07-Jul-19 12:27 AM eEeEeeeeBANG 07-Jul-19 12:27 AM Pinned a message. 07-Jul-19 12:27 AM So like I guess just be safe k? 07-Jul-19 02:02 AM :D 07-Jul-19 02:02 AM i'm excited for my scary new power supply to get here 07-Jul-19 02:02 AM primarily because it has an adjustable current limiter 07-Jul-19 02:02 AM i used to be a lot more cavalier with high voltage as a kid and now i'm a big squeamish baby about it all, s'probably for the best frankly 07-Jul-19 02:06 AM Yep 07-Jul-19 02:06 AM specs of the new supply? 07-Jul-19 02:06 AM 30kV, 32mA; glassman something or other 07-Jul-19 02:06 AM it needs a front meter replaced 07-Jul-19 02:06 AM hopefully nothing else is seriously wrong with it 07-Jul-19 02:07 AM ohh, nice 07-Jul-19 02:08 AM you know what i legitimately really want to build is a van de graaff accelerator 07-Jul-19 02:09 AM damn it, if I was on my PC right now I could send pics of one 07-Jul-19 02:09 AM like presumably just belts and pulleys and suchlike will get you hundreds of kilovolts at however many nanoamps 07-Jul-19 02:09 AM I have one close to me, 14 MV tandem 07-Jul-19 02:09 AM under 6 bar SF6 07-Jul-19 02:09 AM >.> 07-Jul-19 02:11 AM I'm trying to organize a tour through it 07-Jul-19 02:11 AM neat! 07-Jul-19 02:11 AM 'cause it's being shut down for good this year :< 07-Jul-19 02:11 AM oh no 07-Jul-19 02:11 AM what was it used for? 07-Jul-19 02:12 AM everything 07-Jul-19 02:12 AM the reactor close to it does fuel research with it, it's used as a giant microscope, but most of the time it's a mass spectrometer 07-Jul-19 02:12 AM due to a variety of ion sources it can accelerate everything you can ionize 07-Jul-19 02:12 AM but yeah, if you don't need beam current can de graaf might actually be the way to go, easy to regulate and can do 500+ kV with medium effort 07-Jul-19 05:31 AM @qualia that nA of current will be unloaded without beam. As soon as you add beam loading, your voltage will sag a ton unfortunately if your ion gun draws more than that 07-Jul-19 05:31 AM I don't think a working VDG accelerator would be a medium effort past 500 kV. Maybe like 100kv factoring in beam loading issues. 07-Jul-19 05:31 AM However, you could overcome this using a pulsed ion source to inject initial higher current beams and use the VDG to provide the accelerating potential 07-Jul-19 05:31 AM In this way, VDGs can provide beams of a few amps 07-Jul-19 04:06 PM yeah i have heard a couple mentions of chopped-beam VDGs, that seems like a reasonable way to go 10-Jul-19 01:44 AM http://danyk.cz/vn_reg_en.html 10-Jul-19 01:44 AM "Adjustable stabilized switching high voltage supply 7-55kV" 10-Jul-19 01:51 AM nice and simple design 10-Jul-19 10:35 AM ohh that's a really nice design 10-Jul-19 10:35 AM plastic bin chassis is 10-Jul-19 10:45 AM makes it rack-ready - basically 05-Aug-19 03:13 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20190805_001910-757D9.jpg 05-Aug-19 03:13 AM if you've ever wondered what those modules put out: 05-Aug-19 03:13 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/TEK00001_JPG_2-4E026.jpg 05-Aug-19 03:13 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/TEK00001_JPG_3-CB0C3.jpg 05-Aug-19 03:13 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/TEK00001_JPG_1-2654C.jpg 05-Aug-19 01:50 PM 19kV aint that bad 05-Aug-19 01:51 PM and that's just with 3V in, but above ~25 kV they ark over internally 05-Aug-19 01:53 PM Ok. Still looks like a fun toy. 05-Aug-19 01:54 PM they really are 05-Aug-19 01:54 PM really angry little buggers 05-Aug-19 02:07 PM Nice 05-Aug-19 02:31 PM Now... since they put out DC @GigaSquirrel 05-Aug-19 02:31 PM What if you stacked a bunch of them in series, with caps on each node? 05-Aug-19 02:31 PM 10 modules at $3 each and you get 250kV 05-Aug-19 02:32 PM thought about that myself, but you have to keep in mind that the isolation between primary and secondary will in no way isolate 250 kV 05-Aug-19 02:32 PM But each node would only need to isolate 25 05-Aug-19 02:32 PM or 20 to be safe 05-Aug-19 02:33 PM @george and I were thinking about that, PMMA axis and many generators 05-Aug-19 02:33 PM How much current can they push? 05-Aug-19 02:34 PM yet to measure that 05-Aug-19 02:34 PM or rather yet to come up with a way to measure that 05-Aug-19 02:34 PM short circuit current is easy to measure but not very representative 05-Aug-19 02:34 PM You know what, an x-ray tube might be easiest to do in this case 05-Aug-19 02:34 PM Or some tube capable of handling over 25kV 05-Aug-19 02:34 PM yep that was the second thought 05-Aug-19 02:34 PM Slowly ramp the grid/wehnelt/filament voltage 05-Aug-19 02:34 PM But at 25kV, that's perfect for driving my tiny microfocus tubes, which are rated at around 40 05-Aug-19 02:36 PM another point is the definition, how much should the voltage drop to define the current 05-Aug-19 02:36 PM They're not useful for me, but I have two and I might as well build a palmtop microfocus source 05-Aug-19 02:36 PM 2*ripple maybe? 05-Aug-19 02:36 PM For voltage drop 05-Aug-19 02:36 PM so 1 kV 05-Aug-19 02:36 PM that's not going to be much... 05-Aug-19 02:36 PM if it drops 1kV average 05-Aug-19 02:36 PM you should be able to pull a few watts from it if you have some sort of closed loop control to push more power into the oscillator when it's loaded down 05-Aug-19 02:38 PM hmm 05-Aug-19 02:38 PM will try that tomorrow ^^ 05-Aug-19 02:38 PM I'm thinking about powering a small TEA laser with them 05-Aug-19 02:57 PM Heh that would be neat! 05-Aug-19 02:57 PM Damn now I remember that I forgot to take my neon sign transformer with me from my last employer. RIP NST. 05-Aug-19 03:00 PM speaking of, how is your job situation? 05-Aug-19 03:00 PM iirc the latest news weren't great 05-Aug-19 03:08 PM Currently freelance repairing AV gear (mostly big-af led screens) and getting back to school to finish my degree. 05-Aug-19 03:11 PM oh 05-Aug-19 03:11 PM best of luck with your degree! 05-Aug-19 03:12 PM It should be doable. 05-Aug-19 03:12 PM Just re-learning the more academic mindset is gona suck after being 4years in the industry 05-Aug-19 03:12 PM suddenly I have to do actual algebra again :DDDD. Instead of just throwing LTspice and appnotes at problems. 05-Aug-19 03:13 PM oh, I feel very sorry for you 05-Aug-19 03:13 PM And thinking about fun stuff like UL94-V0 certs for wiring harness cables. 05-Aug-19 03:13 PM Hehe yeah. got all the easy stuff done, so all the more fun stuff like semiconductor physics and stuff dealing with laplace transforms left. 05-Aug-19 03:13 PM I wonder if school still has APLAC and MWO licenses. ANd if they have any CST licenses. 05-Aug-19 03:13 PM Speaking of high voltages, I should lashup a quick geiger counter with that 3eur soviet tube I found in the junkbox and one of those 90-450V eBay boost converters. 05-Aug-19 03:13 PM got the boost for making B+ supplies for vacuum tube receivers. 05-Aug-19 03:17 PM uhh 05-Aug-19 03:17 PM what tube? 05-Aug-19 03:17 PM ci-3bg something, the cheapest one can find. 05-Aug-19 03:17 PM One of these http://www.sovtube.com/x-ray-and-geiger-tubes/331-ci-3bg.html 05-Aug-19 03:18 PM ohh, those are... blind 05-Aug-19 03:18 PM expected as much at that price point. 05-Aug-19 03:19 PM fair 05-Aug-19 03:19 PM Threw it in one order years back for giggles. 05-Aug-19 03:26 PM Don't buy a SI-3BG 05-Aug-19 03:26 PM They're beyond blind 05-Aug-19 03:26 PM heh 05-Aug-19 03:26 PM oh btw, @Deleted User you don't have any information about russian detectors by any chance? 05-Aug-19 03:27 PM I mean I speak Russian 05-Aug-19 03:27 PM so yes 05-Aug-19 03:27 PM (let's more this to #radiation ) 18-Aug-19 04:31 PM slightly off topic, but these Chinese single-board tesla drivers are really impressively efficient 18-Aug-19 04:31 PM https://youtu.be/6GnPcXaQSm0 18-Aug-19 04:31 PM 15V in, 40kV out on a completely untuned circuit 18-Aug-19 04:31 PM not sure if I'm even going to bother tuning it, since it more or less PLLs itself, and with 310VDC input, I'm going to see some massive streamers 18-Aug-19 04:31 PM The next step is to test and see if it can handle 310VDC.... 18-Aug-19 10:47 PM https://www.electrotechnicproducts.com/bd-10as-high-frequency-generator/ theese are the hand held Tesla coils we use. They have a vibrating reed that is mechanically tuned with a knob on a screw on the bottom that effectively controls the duty cycle. Very handy for leak testing and just general HV probing. You can instantly find spots in a design where an arc is likely to occur. 18-Aug-19 11:52 PM Not really a tesla coil 18-Aug-19 11:52 PM But yeah, fairly useful 18-Aug-19 11:52 PM I could probably build that in less than a day and certainly for less than $300 18-Aug-19 11:52 PM I've seen them used very often 19-Aug-19 11:17 AM oh i have one of those! ... for .. other purposes 19-Aug-19 11:17 AM is the metal electrode on that socketed? 19-Aug-19 11:40 AM That reminds me of the electric wart remover bigclive tordown at one point 19-Aug-19 06:36 PM Theese last a very very long time and are safe to use, and very resilient. The electrode is socketed on them, and sometimes it is advantageous to actually have a tiny air gap on that socket. Changes the behavior of the arc a bit. 19-Aug-19 06:36 PM Of course when I bought mine they cost a bit less. 19-Aug-19 07:09 PM How zappy are they? 19-Aug-19 07:09 PM Dangerous? 19-Aug-19 07:09 PM If it's a vibrating reed, ignition coil methinks 19-Aug-19 07:09 PM That'd be dangerous 19-Aug-19 07:09 PM But if it's HF, it won't hurt besides the sting 19-Aug-19 11:27 PM They will get you pretty good. It is an ignition coil type of affair but they have a form of high pass filtering in the driver side that basically only allows The chattery noise and harmonics through. I am sure it can be very dangerous if you turn it up all the way but I believe it is also current limited by virtue of secondary impedance so who knows. Not gonna grab the probe directly to find out though! 19-Aug-19 11:45 PM This is why I prefer RF :p 20-Aug-19 11:15 AM i am pretty sure i have one of those exact models of thing; i initially suspected it was indeed a rebranded vacuum leak tester, but i bought it under the auspices of it being a.. toy, of sorts >.> 20-Aug-19 11:15 AM it does indeed have some bite, especially at full power 20-Aug-19 11:36 AM https://pbs.twimg.com/media/DbXNWMUU8AE-oEL?format=jpg bzzt 20-Aug-19 11:43 AM (don't try this at home etc) 20-Aug-19 11:49 AM A toy 20-Aug-19 11:52 AM yeah that 20-Aug-19 11:52 AM but i digress, 20-Aug-19 11:53 AM I like the "safe" nature of HF arcs 20-Aug-19 11:53 AM But I don't like when they sting 20-Aug-19 11:54 AM rather sting than lock up a muscle, i suppose 20-Aug-19 11:55 AM Especially if it's the muscle that makes you grab it harder 20-Aug-19 12:43 PM I've shocked myself a few times with my plasma wand. 20-Aug-19 10:57 PM https://youtu.be/kCnJAr82ifg 20-Aug-19 10:57 PM The cheap driver performs rather well on an untuned crappy coil 20-Aug-19 10:57 PM I've chickened out and decided not to push it further than 120V, because it's DEAFENING 20-Aug-19 11:07 PM nice 06-Sep-19 03:11 PM https://twitter.com/profanegeometry/status/1170088667718701056 new toy :D 06-Sep-19 03:11 PM i wouldn't have bothered getting a P6015, since they need a dielectric fluid to get up to full spec, but i discovered REB3 put together a tech doc on dielectric replacement and recalibration http://www.reb3.com/pdf/AN108.pdf 06-Sep-19 03:28 PM Very nice 06-Sep-19 03:43 PM fingers crossed.. 06-Sep-19 03:43 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Screen_Shot_2019-09-06_at_3.42.46_PM-3A980.png 07-Sep-19 10:10 AM Listings for those on ebay vary in price by about 20x!!! 10-Sep-19 02:43 PM the oil or the probe? 14-Sep-19 10:30 PM The probe 14-Dec-19 05:45 PM Hey everyone this channel is now for lasers as well. So go forth and pew pew! 14-Dec-19 05:45 PM I do want one of those laser skin removal lasers... just seems like too much fun haha 14-Dec-19 05:45 PM though I will want to buy some darn good googles before such a thing even enters the house haha 14-Dec-19 05:45 PM well probably two pairs, one to test the thing against and one to wear... because I wouldn't even trust it at that rate 14-Dec-19 05:45 PM also will probably use a few of my old cell phones for recording anything to do with it since well 14-Dec-19 05:45 PM yea those can die if they want 14-Dec-19 06:09 PM "laser skin removal" 14-Dec-19 06:09 PM Hold on there, Hannibal. 14-Dec-19 06:24 PM o h n o 14-Dec-19 06:24 PM i'm thinking about hooking my gassy little 2mW HeNe thing up to my current-limited glassman supply actually 14-Dec-19 06:24 PM also i haven't stopped thinking about ion cooling since i first learned about it 14-Dec-19 06:24 PM so that might be a mistake i make someday 14-Dec-19 06:26 PM I should probably make a short memey video about burning things with a HeNe 14-Dec-19 06:26 PM But in cinematic 5K... because... I can... 14-Dec-19 06:26 PM Ok i like just got through telling funranium we were being safe 14-Dec-19 06:26 PM So don't screw this up k? 14-Dec-19 06:27 PM Look, I own a HeNe that can burn things 14-Dec-19 06:27 PM That implies I know how to do the safety 14-Dec-19 06:27 PM lmao 14-Dec-19 06:27 PM That is not a thing you can just pick up on eBay 14-Dec-19 06:27 PM one would certainly hope so 14-Dec-19 06:28 PM The laser is too big to fit on my table and my floors are brown 14-Dec-19 06:28 PM I need to buy some black cloth 14-Dec-19 06:28 PM I wonder if laser supercooling is achievable in a home lab vacuum chamber 14-Dec-19 06:28 PM Drop a few cubic microns down below -273C 14-Dec-19 06:28 PM https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTffvrh41dxZlZ2j36AAtN0LPQR6GRBfKGKHvxWHC8GVDSAg1o3&s 14-Dec-19 06:33 PM i'm definitely curious about it, but i don't know the optics side of things well enough 14-Dec-19 06:33 PM magneto-optical trap 14-Dec-19 06:33 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/f76c7401cbfc47e3fe007471b18c0d84-60BBD.png 14-Dec-19 06:33 PM two salad bowls with fancy chicken wire 14-Dec-19 06:33 PM that's amazing 14-Dec-19 06:33 PM and judging by the color, I'm guessing... hene or some weird argon ion mode? 14-Dec-19 06:33 PM you can easily build optical tweezers and drag stuff around with a laser beam 14-Dec-19 06:33 PM that's a 5 minute project 14-Dec-19 06:34 PM i'd like to build a tiny paul trap and a small laser schlieren setup 14-Dec-19 06:34 PM yeh 14-Dec-19 06:35 PM which is a super cool thing 14-Dec-19 06:35 PM you can just take a red laser diode, focus it, and it suddenly quantums your dust 14-Dec-19 07:59 PM Pulled my little laser pointer out 14-Dec-19 07:59 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/toob_bright-761D9.jpg 14-Dec-19 07:59 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/aperture-B6E59.jpg 14-Dec-19 07:59 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/controller_bright-48E35.jpg 14-Dec-19 07:59 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/funky_beam-83BF6.jpg 14-Dec-19 07:59 PM It has the best interlock system ever 14-Dec-19 07:59 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/controller_connector-463E7.jpg 14-Dec-19 08:01 PM hah 14-Dec-19 08:01 PM The controller won't turn on if this little screw that's pushed onto the connector doesn't press the button 14-Dec-19 08:31 PM @Mason_Yu you know what I was thinking... maybe it's possible to DIY a powerful q-switched laser out of eBay parts? 14-Dec-19 08:31 PM There's plenty of ridiculously powerful pump modules well into the 30-50W range 14-Dec-19 08:31 PM Some even above 120 14-Dec-19 08:31 PM And a few q-switches 14-Dec-19 08:32 PM You know, YAG crystals and passive q-switches are not that expensive 14-Dec-19 08:32 PM This guy seems to have done... something(?) 14-Dec-19 08:32 PM https://www.youtube.com/user/w0003947/videos 14-Dec-19 08:32 PM A passive q-switch with an air-cavity yag laser should easily get into the MHz and at least picosecond pulses 14-Dec-19 08:32 PM With a 50W pump and assuming a "crappy DIY" loss of 50%, that's still 25W 14-Dec-19 08:32 PM He even built a mechanically q-switched laser, which is equally funny and impressive 14-Dec-19 08:32 PM Standa makes some very spicy q-switched laser pointers 14-Dec-19 08:32 PM https://www.youtube.com/watch?v=X2Luah-95ik 14-Dec-19 08:32 PM (don't ask them for the price if you don't want to have a heart attack) 14-Dec-19 08:39 PM Huh, only 150 Hz rep rate, it can go higher right? 14-Dec-19 08:39 PM Yeah I think it's just a demo 14-Dec-19 08:39 PM 60mW average output power! 14-Dec-19 08:39 PM 60mW! And air breakdown! 14-Dec-19 08:49 PM tons of Gooch&Housego q-switches on ebay for cheap 14-Dec-19 08:49 PM AOMs though, so need drivers 14-Dec-19 08:49 PM Now those are not cheap 14-Dec-19 08:50 PM Now, to reach the higher powers what's the cheapest way to make the pumping laser diodes? 14-Dec-19 08:51 PM Make? 14-Dec-19 08:51 PM You can buy them over 100W for <$300 14-Dec-19 08:52 PM Oh eBay? I didn't know they were that cheap 14-Dec-19 08:52 PM oh they are dirt cheap 14-Dec-19 08:52 PM not sure if they can be used for pumping though 14-Dec-19 08:52 PM Yeah this is not something just any laser diode will do 14-Dec-19 08:53 PM https://www.ebay.com/itm/nLIGHT-Pearl-P4-050-0808-3-A-R01-30407-Fiber-coupled-Laser/283280851187 14-Dec-19 08:53 PM 50W of 808 for $200 14-Dec-19 08:53 PM inputs shorted, looks clean 14-Dec-19 08:53 PM https://www.ebay.com/itm/nLIGHT-Pearl-P6-080-0808-Fiber-Coupled-Laser/283702162680 14-Dec-19 08:53 PM 80W of 808 with a fiber for $500 14-Dec-19 08:53 PM 40W of coherent 808 for $100 14-Dec-19 08:53 PM https://www.ebay.com/itm/Fiber-for-COHERENT-FAP-800-FAP800-40W-808nm-FIBER-COUPLED-DIODE-LASER/254377484968 14-Dec-19 08:53 PM this one is used in those massive cabinet-sized laser cutter power sources 14-Dec-19 08:53 PM they just stack them 14-Dec-19 08:53 PM the pump bars are even cheaper 14-Dec-19 08:55 PM that last link is just the fiber i think? 14-Dec-19 08:55 PM nope, talked to that seller 14-Dec-19 08:55 PM laser and fiber 14-Dec-19 08:55 PM Hey maybe the factories in China who makes the fiber lasers will be willing to sell components independently, espectially those used in the higher power units for cutting 14-Dec-19 08:56 PM just be careful... "ITEM: Factory fiber, as used on COHERENT HIGH POWER FAPI DIODE (diode pictured is NOT included)" 14-Dec-19 08:56 PM oh, huh 14-Dec-19 08:56 PM "fiber for" 14-Dec-19 08:56 PM ouch 14-Dec-19 08:56 PM well, no worries, there's plenty of others 14-Dec-19 08:56 PM @Mason_Yu maybe, but what about the other parts? 14-Dec-19 08:56 PM I still have no idea on how exactly pumped q-switched lasers are made 14-Dec-19 08:56 PM Even the Tech Ingredients video is not very clear about it 14-Dec-19 08:56 PM And that's the best material on youtube 14-Dec-19 08:56 PM toooons of these though 14-Dec-19 08:56 PM https://www.ebay.com/itm/COHERENT-FAP600-35W-804-0-Laser-Diode-1141810/283350140354 14-Dec-19 08:58 PM when i saw the Strange Parts video that went up today (?) i was hoping they would delve into the actual laser heads instead of just a general overview of the machines 14-Dec-19 08:58 PM https://www.repairfaq.org/sam/lasercds.htm 14-Dec-19 08:58 PM still was cool to see some of that stuff but talk about a let down 14-Dec-19 08:59 PM 804 nm should work for pumping 14-Dec-19 08:59 PM from what I understand that's the wavelength for vanadate pumping 14-Dec-19 08:59 PM frequency doubling is not important for us, so the KTP crystal and its finicky bell curve is not needed there 14-Dec-19 08:59 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Experimental-setup-of-a-diode-end-pumped-a-51EFB.png 14-Dec-19 08:59 PM BBO is... beam blanker optics? 14-Dec-19 08:59 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Schematic-diagram-of-laser-diode-end-pumpe-15F52.png 14-Dec-19 08:59 PM yeah it's definitely 808 14-Dec-19 08:59 PM so cheap lasers are available, but what about the other parts 14-Dec-19 08:59 PM I don't think you can just stick any random Gooch&Housego AOM into the path and expect it to work 14-Dec-19 09:03 PM That's interesting, you'd need to increase the brightness, not just power of the pumping diode, therefore the focusing optics are necessary 14-Dec-19 09:03 PM yes 14-Dec-19 09:03 PM I believe what you need is to focus the laser spot on the surface of the crystal 14-Dec-19 09:04 PM Yep 14-Dec-19 09:04 PM And the crystal has to be stabilized 14-Dec-19 09:04 PM BBO is barium borate? 14-Dec-19 09:05 PM looks like we don't need it 14-Dec-19 09:05 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Experimental-setup-of-a-diode-end-pumped-a-769A7.png 14-Dec-19 09:05 PM looks so deceptively simple on the schematic 14-Dec-19 09:06 PM So, cheap output couplers are also available from China 14-Dec-19 09:06 PM I think this is something like a $300 shopping cart at thorlabs 14-Dec-19 09:06 PM ignoring the weight-in-gold optical table 14-Dec-19 09:06 PM but that can be replaced by an oversized aluminium heatsink and some air 14-Dec-19 09:06 PM oh, hey, look 14-Dec-19 09:06 PM exhibit A: 14-Dec-19 09:06 PM https://www.ebay.com/itm/Nd-YVO4-CRYSTAL-for-DPSS-LASER-Marker-1064nm-High-Power-808nm-diode-Pump/254380070392 14-Dec-19 09:06 PM pumped by the good ol jenoptik blue blobs 14-Dec-19 09:06 PM https://www.ebay.com/itm/Nd-YVO4-DPSS-LASER-Marker-1064nm-Tested-10w-808nm-diode-Pump-Jenoptik-JOLD-30/254391922272 14-Dec-19 09:09 PM Hey it looks just like the schematic minus the focusing optics 14-Dec-19 09:09 PM and minus the q switch 14-Dec-19 09:09 PM wait no, it's right there 14-Dec-19 09:09 PM that red looking RF voodoo thing 14-Dec-19 09:09 PM okay, so here comes the question: why does this look so simple? 14-Dec-19 09:09 PM and a followup question: if it was this simple, the Chinese manufacturers would've made them dirt cheap, right? 14-Dec-19 09:09 PM what's the catch... 14-Dec-19 09:12 PM I think it's in the pumping diode afterall, scaling it up in power does not seem very trivial 14-Dec-19 09:12 PM well, look at that Jenlas pump, only 30W for ">10W" output 14-Dec-19 09:15 PM No, what I mean is pumping the gain medium with a high power diode. Something related to power density inside the crystal and width of pump beam being too large 14-Dec-19 09:15 PM hm 14-Dec-19 09:15 PM well, the width is always adaptable 14-Dec-19 09:16 PM You might get different modes in that case 14-Dec-19 09:16 PM I don't know enough about high power laser pumping to comment on the exact consequences though 14-Dec-19 09:16 PM do we care about lasing modes? 14-Dec-19 09:16 PM I'm fine with a weird mode mix as long as the beam is ok 14-Dec-19 09:16 PM this listing shows that small crystals seem to take a high power pump fine 14-Dec-19 09:16 PM https://www.ebay.com/itm/Nd-YVO4-CRYSTAL-for-DPSS-LASER-Marker-1064nm-High-Power-100w-pump-4x4x30-mm/254435355408 14-Dec-19 09:16 PM http://www.sintecoptronics.com/catalog/qswitch.pdf 14-Dec-19 09:16 PM here's pretty much the entire ebay catalog of q-switches 14-Dec-19 09:16 PM with datasheets 14-Dec-19 09:16 PM lol 14-Dec-19 09:24 PM I'm looking at the exact same document lol 14-Dec-19 09:24 PM Those q-switches are super cheap, and seems to handle 100W just fine 14-Dec-19 09:25 PM and we're back to approaching $500-600 for an experiment 14-Dec-19 09:26 PM They are actually used in Chinese laser engravers 14-Dec-19 09:26 PM though this, if functional, could output WAY more than 20W 14-Dec-19 09:26 PM G&HG? 14-Dec-19 09:26 PM Yep, look at the origin, all shipping from China 14-Dec-19 09:26 PM they're the biggest name 14-Dec-19 09:26 PM https://www.ebay.com/itm/Neos-Driver-N38027-50DMPK-Gooch-Housego-LASER-optic-RF-Driver/333380458046? 14-Dec-19 09:26 PM driver to go 14-Dec-19 09:26 PM I'm guessing 27MHz 50W 14-Dec-19 09:26 PM wait a second... 27MHz, isn't that the CB radio range? 14-Dec-19 09:26 PM I suppose a CB radio transmitter can't be switched on and off at 50kHz 14-Dec-19 09:26 PM https://www.ebay.com/itm/GOOCH-HOUSEGO-R38027-50DMPK-PL1-A-MOTOR-DRIVE/283489288241 14-Dec-19 09:26 PM yes sir, it's totally a motor driver, absolutely, $60 it is 14-Dec-19 09:33 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IWDS038-V1.0-MQH0XX-YYDM-ZZZ-RF-Driver-Cop-9D173.pdf 14-Dec-19 09:33 PM Driver datasheet 14-Dec-19 09:33 PM 27MHz is CB radio range, but 27.12MHz is also a very popular industrial heating & plasma generation band 14-Dec-19 09:34 PM "up to 100kHz pulse rate" 14-Dec-19 09:34 PM don't think a CB radio or plasma supply can do that 14-Dec-19 09:34 PM that AOM power supply is actually super interesting 14-Dec-19 09:36 PM It would take much more than $60 to make this yourself I think 14-Dec-19 09:36 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-FADD8.png 14-Dec-19 09:37 PM well that's just chopping 14-Dec-19 09:37 PM fancy chopping 14-Dec-19 09:37 PM A is rising edge pulse, B is just on-off keying, and C is analog modulation 14-Dec-19 09:37 PM the latter we don't really need, since laser output power is controllable through the pump input 14-Dec-19 09:37 PM (and you don't want to dump 30W into the q-switch) 14-Dec-19 09:43 PM https://www.ebay.com/itm/NEW-High-Power-Laser-Diode-20W-808nm-1cm-50-Emitter-CS-Bar-for-DPSS-Pump-CS-01/113347585663 14-Dec-19 09:43 PM Oh sorry for the link 14-Dec-19 09:43 PM you can drop everything after number? 14-Dec-19 09:43 PM diode bars are not the way to go 14-Dec-19 09:43 PM they need collimation and the whole shoving-through-the-fiber thing regardless 14-Dec-19 09:43 PM so it's far easier to buy pre-coupled arrays 14-Dec-19 09:44 PM The thing is you might be able to make an array out of them? 14-Dec-19 09:45 PM you might 14-Dec-19 09:45 PM but it's not going to be easy or cheap 14-Dec-19 09:46 PM I know it's more complicated on the pumping optics but it will provide a cheaper way to scale up. As it is we're paying $500-$600 in the major components alone for a lower power laser 14-Dec-19 09:46 PM the alignment and parts inside are critical 14-Dec-19 09:46 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/maxresdefault-0A065.png 14-Dec-19 09:46 PM this kind of stuff 14-Dec-19 09:46 PM https://www.youtube.com/watch?v=lk02GYJwXZo 14-Dec-19 09:46 PM here's an assembly of these laser bars 14-Dec-19 09:46 PM in short: not worth the pain 14-Dec-19 09:46 PM placing and aligning an army of optical dinguses(most of which are unobtainium by the way) to within microns 14-Dec-19 09:48 PM Well, although I'm impressed by the power I know it's not suitable for a first prototype 14-Dec-19 09:48 PM you can still get a 30, 50, or even 100W single-package 808 laser 14-Dec-19 09:48 PM 100W pump power would get us around 30-40W output power, I think 14-Dec-19 09:51 PM Still sounds a bit optimistic? In Sam's Laser FAQ they got 5W output power from a 50W pump diode 14-Dec-19 09:51 PM and in that ebay listing posted earlier it was 3:1 14-Dec-19 09:51 PM 10W output with a 30W pump 14-Dec-19 09:54 PM Sams might also just be old? 14-Dec-19 09:55 PM As requested by @AdamMcCombs, laser safety officer is now ONLINE. 14-Dec-19 09:55 PM We are unstoppable in our wild thoughts! 14-Dec-19 09:55 PM :D 14-Dec-19 09:57 PM Sweet jeebus. I am in the damn channel description. 14-Dec-19 09:58 PM Yeah hope you don't mind 14-Dec-19 09:58 PM I wanted to make it clear this is not like another laser powered discord 14-Dec-19 09:58 PM I don't. Just...shocked. 14-Dec-19 09:59 PM Judging by the response it seems to have worked 14-Dec-19 09:59 PM @Mason_Yu look at it this way, in terms of input power 14-Dec-19 09:59 PM The 20W Chinese lasers consume around 150W 14-Dec-19 09:59 PM Which means they are spending probably around 40-50W on the q-switch 14-Dec-19 09:59 PM And given laser efficiencies... the pump lasers can't be that powerful 14-Dec-19 10:00 PM I'm concerned about losses in the focusing optics on the pumping side too, not too necessary for a fiber laser on a low power 14-Dec-19 10:00 PM I looked around the styro pyro server for all of a few minutes before slowly back out the room, closing the door, and running. 14-Dec-19 10:01 PM The fiber lasers generally pump the specified light out through the fiber, the losses are accounted for 14-Dec-19 10:01 PM Also, the old 808nm pump lasers on eBay might not have their full rated power at the end of life 14-Dec-19 10:01 PM So we'll maybe lose a watt or two above the lifespan 14-Dec-19 10:01 PM @AdamMcCombs Hah, yeah they be like that. 14-Dec-19 10:01 PM Considering the channel and types of videos, you can imagine the crowd it pulls in. 14-Dec-19 10:01 PM Yeah 14-Dec-19 10:01 PM It is never good when the International Laser Safety Conference uses you as an object lesson. 14-Dec-19 10:02 PM Lol really? 14-Dec-19 10:02 PM Really. 14-Dec-19 10:02 PM Damn 14-Dec-19 10:02 PM Was it the laser bazooka? 14-Dec-19 10:02 PM It was something of a greatest hits reel. 14-Dec-19 10:03 PM Hah, so I guess it was quite long. 14-Dec-19 10:03 PM I bet it was quite the sight to those who were not already familiar with him 14-Dec-19 10:05 PM OD6-7+ glasses for these kinds of lasers are priiicy 14-Dec-19 10:05 PM But back to laser efficiencies, wall power to CW, we're pretty happy if we can get as high as 20% conversion for laser diode. 14-Dec-19 10:05 PM Which is good news here 14-Dec-19 10:05 PM You lose a bit more to the QSW, but not nearly as much as the inherent inefficiencies. 14-Dec-19 10:05 PM because that means the Q-switched ND:YVO4 laser topology is efficient 14-Dec-19 10:05 PM Is it weird that I can't find glasses that have good notches at 808 and 1064? 14-Dec-19 10:07 PM And as you double and triple frequencies, adding more things you need high OD at, the laser safety glasses get even more expensive. 14-Dec-19 10:07 PM It's either super nice at one or the other, or meh at both 14-Dec-19 10:07 PM It isn't weird for absorptive filter glasses. 14-Dec-19 10:07 PM If you want both you pay through the nose. 14-Dec-19 10:08 PM With these laser powers I want to be certain that a reflection of a reflection of a reflection of a mention of the laser light can't fry me forever 14-Dec-19 10:08 PM For thin film coating style glasses 14-Dec-19 10:09 PM OD7+ at 800-1600 is... $500. Ouch. 14-Dec-19 10:10 PM This is another concern for me if we choose the DIY route, all those exposed parts at high power seems quite a bit more dangerous. Proper enclosure+safety gear is yet more money I don't have 14-Dec-19 10:11 PM In theory the payoff is much bigger than if it's an off the shelf one 14-Dec-19 10:11 PM Yeah one of the reasons why I don't have high power lasers. 14-Dec-19 10:11 PM But this is a "project in and of its own" kind of endeavor 14-Dec-19 10:12 PM As I've often taught in classes, plenty of people have burned or blinded themselves with lasers but if they ever died, they were vaporized and no one missed them. The power supplies, however, regularly kill people in the laser industry. 14-Dec-19 10:12 PM The power supplies are harmless puppies in this case 14-Dec-19 10:12 PM If you don't count the AOM RF power supply 14-Dec-19 10:13 PM Now, there's a lot to be said for a $580 fully enclosed 20W fiber laser then. I honestly don't need more power than that 14-Dec-19 10:13 PM Me neither, but all the equipment that adds to that... 14-Dec-19 10:13 PM If the whole kit was $580 I'd already be playing with it 14-Dec-19 10:14 PM I mean, I think you're looking at quite a bit more for a full complete home-made system here... Yes, there's greater potential for scaling but lots of unknowns in each component you pick 14-Dec-19 10:14 PM i bought a crap handheld 50mW green thing many many years ago without realizing what i was getting myself into, and, of course, it has no IR filter. i bought it for pointing at stars and then shortly thereafter realized absolutely nowhere i've lived in the last decade is far enough away from an airport to do so safely 14-Dec-19 10:15 PM I think it's a fun project to do separately 14-Dec-19 10:15 PM Once an actual application is running already 14-Dec-19 10:15 PM Agreed, I'm surprised at just how cheap some of the pumping lasers are lol 14-Dec-19 10:15 PM With an air cavity system there's potential to build a 20W+ picosecond laser 14-Dec-19 10:15 PM With megawatts at megahertz 14-Dec-19 10:15 PM That's the tempting part 14-Dec-19 10:16 PM tabletop terawatt! tabletop terawatt!! 14-Dec-19 10:16 PM This is also why LSOs everywhere despair. 14-Dec-19 10:16 PM If it was just DIYing the same 20W Chinese laser, it'd be pointless 14-Dec-19 10:16 PM femtos are obviously not happening, but picoseconds is within the realm of CW seed pumping 14-Dec-19 10:16 PM (it's literally right there in the name of the AOM, 27MHz) 14-Dec-19 10:16 PM now that makes me wonder 14-Dec-19 10:18 PM Shorter pulses is the only reason I'm looking at the active q-switches too, but that seems to be the only component that's absolutely needed. 14-Dec-19 10:18 PM ... can a Chinese laser have the AOM replaced with a 27MHz one? 14-Dec-19 10:18 PM you'd have a... pulsed pulsed laser 14-Dec-19 10:18 PM since the seed is the nanosecond source 14-Dec-19 10:18 PM wait, I totally derped just now 14-Dec-19 10:18 PM 27MHz is the static input power, the switching rate is up to 100kHz 14-Dec-19 10:18 PM nevermind, stupid idea 14-Dec-19 10:20 PM So, for your 808-1100nm needs at high OD I do have a recommendation for you at a relatively reasonable price: https://www.lasersafety.com/product-category/eyewear/?sfilter=1&od_ranged=1&range_0=808&od_0=7&really_curr_tax=20-product_cat 14-Dec-19 10:20 PM This is a very common filter we use for our labs. 14-Dec-19 10:21 PM a measly quarter of the total budget 14-Dec-19 10:21 PM lol 14-Dec-19 10:21 PM though I think with the Chinese laser there won't be a need for 808-1100, it's just 1064 14-Dec-19 10:21 PM but they're all $199 or $179 on the site 14-Dec-19 10:22 PM This page is worth bookmarking as Laservision does good work with reliable filters. And they're working with researchers to try to solve the ultrafast bleaching problem. 14-Dec-19 10:22 PM with one exception 14-Dec-19 10:22 PM https://www.lasersafety.com/product/p5k01/ 14-Dec-19 10:22 PM but it's still $160, and only protects from 1064 14-Dec-19 10:22 PM which is fine for the prebuilt laser 14-Dec-19 10:23 PM Another very common filter. 14-Dec-19 10:24 PM need to start searching for some scratched up filters 14-Dec-19 10:24 PM only buy one filter for one eye, tape the other one 14-Dec-19 10:24 PM Or just get the eye patch 14-Dec-19 10:24 PM laser eyepatch 14-Dec-19 10:24 PM That is an option... 14-Dec-19 10:25 PM wait, are they $160 a PIECE? 14-Dec-19 10:26 PM No, comes with choice of frame. 14-Dec-19 10:27 PM group buying one pair of glasses is a compromise 14-Dec-19 10:27 PM dibs on the left eye lens 14-Dec-19 10:28 PM Right, off to go make more ultracoffee. Lase well. 14-Dec-19 10:29 PM Thanks for joining in! 14-Dec-19 11:59 PM oh, this channel is new! 14-Dec-19 11:59 PM welcome to the new people in the new Channel 15-Dec-19 12:23 AM It's the old high voltage channel 15-Dec-19 12:23 AM Except it's now lasers and high voltage 15-Dec-19 12:23 AM ah, not new, only reburbed 15-Dec-19 12:51 AM oh laser 15-Dec-19 12:52 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/hqdefault-75258.png 15-Dec-19 12:53 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-D7EFE.gif 15-Dec-19 12:53 AM just randomly using this gif 15-Dec-19 12:53 AM yeah I mean we need wakefield acc for teh GeVs and TeVs 15-Dec-19 01:07 AM We would still need chirp pulse amplification to make wakefield accelerators feasible 15-Dec-19 01:07 AM For electrons anyway 15-Dec-19 01:07 AM An pulsed electron beam driven design might in fact be slightly more feasible for the dedicated hobbyist 15-Dec-19 08:25 AM y? 15-Dec-19 08:25 AM I mean y it's harder for lasers? 15-Dec-19 08:25 AM cause of the ... source for diffraction gratings? 15-Dec-19 08:30 AM Yes, generating the femptosecond pulse itself is a challenge, but there's so much beyond that too for a laser driven wakefield accelerator 15-Dec-19 08:30 AM For a home system I cannot imagine a long plasma volume, so everything becomes tighter, time of injection, energy of injection, all of the plasma parameters... etc. 15-Dec-19 08:30 AM Whereas in an electron driven wakefield, divergence of relativistic driving beam is not significant and it can happen over a much longer length due to lack of dephasing 15-Dec-19 08:30 AM The catch here is the source of driving electrons. If accelerators like EXEDA from @Applied_Ion becomes a possibility, it is certainly possible to do it for a hobbyist 15-Dec-19 08:30 AM Though, GeVs and TeVs probably have to wait 15-Dec-19 09:26 AM Yeah lol, MeV is possible, generating higher gradients though is just not practical. Lot of new stuff to be done with MeV at amateur level lol 15-Dec-19 09:27 AM Stupid Question: Seeing the other day the dumb video from styropyro about the "1.000.000 watts" tatoo removal laser, that at it's focal point just plasmo-ed the air. I was wondering, what would happen if you made a fusor but instead of powering the grids to enough voltage potential to fuse, you just mantained the plasma in one place, then fired one or more of those lasers at the center of the plasma. 15-Dec-19 09:27 AM (No, not even considering it, just asking the question out of curiosity) 15-Dec-19 09:30 AM Certainly some valid science to be done with laser-plasma interactions at the amateur level. Not sure it would do too much realistically for a fusor though. Takes a lot more effort to ionize gas with a laser than just straight up electrical ionization 15-Dec-19 09:31 AM he asked for a friend 15-Dec-19 09:32 AM I don't think you would see much practical benefit, I'd just say it's better to just pulse the whole fusor lol. 15-Dec-19 09:32 AM If you held weak ionization, to maintain a glow, you could fire the laser and see if you can detect some increase neutron production, but I don't think you would detect a ton 15-Dec-19 09:32 AM Shouldn't actually be a hard experiment though. UV transparent viewport, and adjust the focal length the the center. 15-Dec-19 09:38 AM yeah but not directly with the Nd:YAG 15-Dec-19 09:38 AM which is IR btw 15-Dec-19 09:38 AM but you can use it (the Nd:YAG) as a pumping source of course 15-Dec-19 09:41 AM I'd say a fusor configuration wouldn't be right 15-Dec-19 09:41 AM You would want higher fuel density for spark neutron production 15-Dec-19 09:41 AM and yeah I guess you need a very short pulse/ high power laser for generating significant amounts of neutrons, right? 15-Dec-19 09:42 AM @N00N totally for a friend, yes. 15-Dec-19 09:42 AM ^^ 15-Dec-19 09:43 AM Confinement time and plasma volume would be really bad if you just fire a focused laser beam into low pressure deuterium 15-Dec-19 09:43 AM Lithiundeuteride! 15-Dec-19 09:43 AM Lithium 15-Dec-19 09:44 AM Would be valid if you perhaps need some initial ion source, but really energy inefficient otherwise 15-Dec-19 09:44 AM Electrical pinches exploit compression much better 15-Dec-19 09:44 AM Li(d, t) 15-Dec-19 09:45 AM For the safety POV, just for reference from professional experience, any modestly successful neutron generator is also an unacceptably incidental successful x-ray generator. 15-Dec-19 09:45 AM Yeah 15-Dec-19 09:45 AM but the guys are always into x-ray fun 15-Dec-19 09:45 AM Friends don't let friends build fusors willy nilly. 15-Dec-19 09:46 AM "if the counter's clicks it makes 'em kicks" 15-Dec-19 09:46 AM CURRENT COUNT OF GARAGE FUSOR PHIL HAS PREVENTED FROM IRRADIATING THE NEIGHBORS: 5 15-Dec-19 09:47 AM XDD 15-Dec-19 09:47 AM To be fair, friend's neutron radiography project did sound pretty boss. 15-Dec-19 09:47 AM Oh, we have a funranium here too? 15-Dec-19 09:47 AM You have THE funranium. 15-Dec-19 09:47 AM most persone in here are rick sanchez style mad, i guess 15-Dec-19 09:47 AM ehehe awesome! 15-Dec-19 09:47 AM Excuse me, Sir Funranium. 15-Dec-19 09:48 AM No American can accept titles or ennoblement. 'Tis a rule. 15-Dec-19 09:48 AM Re: LiD Breeding tritium in-situ does not solve the confinement issue, you'd still need to heat and compress the resultant plasma to get appreciable fusion reactions. Unless what you are proposing is a NIF at home 15-Dec-19 09:48 AM Okay, SIR Funranium. 15-Dec-19 09:48 AM What neutron radiography project? 15-Dec-19 09:48 AM All coming together. 15-Dec-19 09:49 AM With what neutron source? A fusor? Pulsed sources? Beam driven? 15-Dec-19 09:50 AM Had a friend very fond of esoteric photography methods, the weirder the better. He was going to slap together a Farnsworth Fusor and go to town. 15-Dec-19 09:50 AM Huh, must be a hell of a fusor then. Need a lot of neutrons for something like that and need to shield for x-rays too 15-Dec-19 09:51 AM It never happened. That was the starting point of the practicality argument for "Don't do this." 15-Dec-19 09:51 AM IBR style source 15-Dec-19 09:52 AM The cadmium film cassettes would also be tricky and somewhat toxic. I offered to introduce him to Aerotest if he really wanted to do this. 15-Dec-19 09:53 AM So nuetron photography? 15-Dec-19 09:53 AM driving his neutron chopper down town :3 15-Dec-19 09:53 AM Just imagining thermal flux? 15-Dec-19 09:53 AM Hm 15-Dec-19 09:53 AM That might actually be really useful 15-Dec-19 09:54 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/PhoenixNuclearLabs-C870C.png 15-Dec-19 09:54 AM This is from a D-D beam on target source with a massive >10^12 neutron generation rate 15-Dec-19 09:55 AM lel perfect cover image for a scene mag 15-Dec-19 09:55 AM Yeah I just don't know how you get that coherent of a source from a garage fusor 15-Dec-19 09:55 AM Yeah I had a friend who worked at Phoenix for a while 15-Dec-19 09:56 AM You don't. That's another part of the practicality argument. 15-Dec-19 09:56 AM I've got a problem right now trying to localize where exactly fusion is happening in a garage fusor and a film method might be nice 15-Dec-19 09:56 AM You just fill your garage with x-rays for funzies. 15-Dec-19 09:57 AM Now I should add this garage fusor has a 2000lb full castle shield on it 15-Dec-19 09:57 AM His would not have. 15-Dec-19 09:57 AM And is registered with the state and regularly inspected 15-Dec-19 09:58 AM Which is part of the later arguments of "If you REALLY want to do this, there's some stuff you need to do..." 15-Dec-19 09:58 AM The system is running in a beam on target mode right now and because the beam hits 2 sides of the vessel doing the math for isotropic output is hard 15-Dec-19 09:58 AM Because it's nowhere near a point source 15-Dec-19 09:59 AM May I recommend long scintillators/scintillating fibers? 15-Dec-19 10:00 AM I can detect 2 lobes of thermalized nuetrons near the ends of the reactor where it's close to the shield so I've got edvidenc it's definitely not a point source 15-Dec-19 10:01 AM You would scan a vertical scintillating fiber across the volume you're intersted and build up an idea of neutron source distribution in one dimension (horizontal) 15-Dec-19 10:01 AM Yeah that's a good idea 15-Dec-19 10:01 AM Saint-Gobain gives samples out for free if you call and ask nicely 15-Dec-19 10:03 AM I was thinking of mapping the flux on the outside with our proton recoil detector and then try to use mcnp to reverse out a probability map of where the nuetrons are coming from. But I'm definitely not good enough at mcnp to do that yet 15-Dec-19 10:03 AM is such doped polystyrene foo pricey? 15-Dec-19 10:04 AM I'm not sure if this complex deconvolution is actually possible in MCNP..... 15-Dec-19 10:04 AM Or any Monte Carlo simulations 15-Dec-19 10:04 AM Me neither 15-Dec-19 10:04 AM But the friend who would know is in town this week 15-Dec-19 10:04 AM So I'm going to find out 15-Dec-19 10:05 AM Just due to how the simulation works. You can solve transport equations backwards to get an exact source term but probablistic simulations is another story 15-Dec-19 10:06 AM Hm 15-Dec-19 10:06 AM The extent of my experience with mcnp is very basic transport simulation so this is pretty far outside of my depth 15-Dec-19 10:07 AM You can certainly just brute force it with many parametrized simulations if you make assumptions about your source distribution 15-Dec-19 10:07 AM This is what's abusing my laptop right now lol, not a good idea to run MC sims for two weeks straight (OpenMC instead of MCNP) 15-Dec-19 10:10 AM Lol 15-Dec-19 10:14 AM @N00N The doped poly is actually really reasonable in price 15-Dec-19 10:15 AM everything to solve blind convolution is handy for that, right? 15-Dec-19 10:15 AM Scintillating fibers with ~200 micron core diameter is ~$20 per meter 15-Dec-19 10:15 AM hmm sounds ok 15-Dec-19 10:15 AM and the whole topic interesting 15-Dec-19 10:19 AM Not related to lasers or high voltage though 15-Dec-19 10:32 AM yeah 15-Dec-19 10:32 AM don't have a neutron source 15-Dec-19 10:32 AM not yet!! 15-Dec-19 10:59 AM https://www.youtube.com/watch?v=r5vsUta5lmo 15-Dec-19 11:10 AM The laser cutting industry is very much still just packing as many laser bars into a cabinet as the customer requests 15-Dec-19 11:10 AM You can go up to hundreds of kilowatts if you're a billionaire 15-Dec-19 12:21 PM Holy moly you're not kidding about Styropyro's discord 15-Dec-19 12:21 PM pun intended 15-Dec-19 12:22 PM Yeah 15-Dec-19 12:22 PM Thus the laser safety thing 15-Dec-19 12:57 PM I'm almost tempted to look myself, but it's probably upsetting to see for people serious about this stuff lol 15-Dec-19 12:58 PM Please don't 15-Dec-19 12:58 PM I'm not sure if that was a positive or negative statement about that discord 15-Dec-19 01:12 PM Negative lol 15-Dec-19 01:14 PM ah well 15-Dec-19 01:18 PM It's almost sad talking to them 15-Dec-19 05:36 PM When a student (usually a student), points at styropyro's body of work and says "But what about this?" when complaining about the laser and lab safety rules he (almost always he) has to follow, I point out that unlike the comments section of YouTube the are professionals with a professional interest and responsibility trying to keep him from going blind, injuring others, and endangering the university's ability to do further research. To quote myself from many of these converstions "I'm not just your LSO to keep you from hurting yourself. You can do that on your free time. I'm here to remind you there's a world beyond the very narrow vision of your work and make sure you get to keep working." Because the philosophy I keep trying to get my colleagues supporting research work to embrace is "The answer is never No, but it might take a lot of work to get to Yes." It also makes the safety collaborative with research and, in my opinion, fun. The number of times I've had to use the Voice of Command to get people to knock it off or hit the EPO to kill work in progress I can count on one hand. 15-Dec-19 05:38 PM Hitting epo must really get their attention 15-Dec-19 05:38 PM I can only imagine the circumstance under which that's required 15-Dec-19 07:15 PM Well, we had blinded someone the previous day and I needed to do an accident investigation... 15-Dec-19 07:16 PM Oh wow that must be one of the worst parts about being lso and rso is dealing with what happens when things go wrong 15-Dec-19 10:01 PM FWIW I don't think hobbyist femto is out of the realm of possibility. By far the most difficult/expensive aspect is instrumentation, but actual construction is on the level of having a splicer that can handle polarization maintaining fiber. E.g. an erbium doped fiber laser using passive mode locking via non-linear polarization rotation is easily < $1000 in components (not factoring in tools - e.g. splicer and optical spectrum analyzer) 15-Dec-19 10:07 PM Yeah, timing, tools and instrumentation is really really expensive though. And if you want to use it for something (e.g wakefield accelerator) it gets even more complicated and expensive 15-Dec-19 10:08 PM @Metanoic It's not necessary to own all the tools. Many companies have these Fujikura's - and ether you can find someone who works on them or pay some money to the company. Could be some 100$ to splice everything. But solid state femtosecond lasers could be more straightforward at home. 15-Dec-19 10:09 PM The point is not only getting femptosecond pulses but high power ones, can solid-state get to the same level of power as CPA? 15-Dec-19 10:09 PM I don't think your common telco fujikura splicers can handle the polarization fiber 15-Dec-19 10:09 PM well it would definitely be a trial/error process with the lengths of active fiber and the like, so paying for splices third party isn't especially doable 15-Dec-19 10:09 PM yes most telco splicers do not handle polarization maintaining fiber, but they can be altered to an extent 15-Dec-19 10:09 PM with that said it should be possible to just... hack it 15-Dec-19 10:09 PM toss out the parts that don't fit, make your own 15-Dec-19 10:09 PM the splicers are really simple when you get down to it 15-Dec-19 10:10 PM e.g. I modified a FSU-975 to let me twist the fiber and hold it proper 15-Dec-19 10:10 PM Probably external twist could be more feasible. When you insert pre-rotated fiber into machine 15-Dec-19 10:11 PM I'm working on a fiber puller/splicer co2 laser system at the moment, IMO is way more practical than arc fusion splicers 15-Dec-19 10:11 PM and fun/weird/awesome stuff happens when you make a fiber nanometers in diameter 15-Dec-19 10:12 PM I know one thing about super thin fibers 15-Dec-19 10:12 PM You can couple multiple fibers together using a tapered inner core! 15-Dec-19 10:12 PM photons keep going in a straight line for a while even after the core disappears 15-Dec-19 10:13 PM it's generally the evanescent wave that does the coupling in fused taper couplers 15-Dec-19 10:13 PM that's another aspect of the co2 system I'm working on, making fused biconical tapers and the likes 15-Dec-19 10:14 PM fused biconical taper is the term I didn't remember 15-Dec-19 10:15 PM more particularly you'd want adibiatic (sp?) tapered couplers 15-Dec-19 10:15 PM *adiabatic 15-Dec-19 10:15 PM light does super weird things when it's shoved down these magical photon tubes 15-Dec-19 10:15 PM even moreso when they're too small to be tubes! 15-Dec-19 10:15 PM the internet is a series of mirrors 15-Dec-19 10:16 PM e.g. supercontinuum generation, or all-fiber harmonic generation 15-Dec-19 10:16 PM merely making a small diameter choke point in a fiber results in crazy stuff 15-Dec-19 10:16 PM another thing I want to work towards is a co2 fiber draw tower similar to the one they made for the ligo mirror suspension 15-Dec-19 10:16 PM https://iopscience.iop.org/article/10.1088/1361-6382/aacf81 15-Dec-19 10:28 PM I will confirm, hobbyist femto isn't out of the realm of possibility. A reasonable Vegas bankroll will let you build one. But my word of warning is that you want to buy BRAND NEW EYEWEAR for this. Since 2018 the reputable manufacturers have been testing and certifying for bleaching effects. Older stuff? No guarantee it'll work. 15-Dec-19 10:38 PM another reason I won't be building one any time soon! :D 15-Dec-19 10:39 PM but you can build the stuff you need your self 15-Dec-19 10:39 PM measurement equip etc 15-Dec-19 10:50 PM the most complex tool(set) would be the splicer/fiber processor - if you want dealing with them, right? 15-Dec-19 10:50 PM but a sub-ps Ti:Sapphire laser doesn't need that? 15-Dec-19 10:57 PM for strictly the assembly part, yea a splicer is the costly item.. though I suppose with extreme patience you could do fc/apc termination by hand (IMO you'd throw you polishing puck across the room after #3 though) 15-Dec-19 10:57 PM an optical spectrum analyzer is helpful in achieving mode-locking or gauging how far off you are 15-Dec-19 10:57 PM as far as ti:sapphire goes I can't speak with authority but I know the gain medium itself doesn't come particularly cheap 15-Dec-19 11:00 PM but you don't need a super high res osa? 15-Dec-19 11:00 PM no, you could surely get by with a DIY wavemeter sort of setup 15-Dec-19 11:00 PM yeah 15-Dec-19 11:00 PM simple michelson would do I guess 15-Dec-19 11:01 PM when you get down to characterizing pulses and whatnot things would get hairy, but merely as a feedback device especially when using nonlinear polarization rotation or, specifically, paddle-type or waveplate polarizers, some rudimentary OSA would let you keep sane 15-Dec-19 11:01 PM my favorite is an equal path fiber interferometer using piezo tubes to stretch one arm 15-Dec-19 11:01 PM relatively limited scan distance but extremely fast 15-Dec-19 11:01 PM and, of course... as will all things monolithically fiber.. no alignment headaches and less susceptible to environmental issues 15-Dec-19 11:01 PM long story short on that is wrap unjacketed fiber around a radially expanding piezo cylinder and oscillate, treat it the same as any other fourier transform interferometer 15-Dec-19 11:06 PM Fiber has been a major step forward in femto work. You lose a lot of power, but if the goal is chirping and any color you like? Let the power go and just smile at Dial-A-Wavelength. 15-Dec-19 11:09 PM not sure I agree on the losing a lot of power part.. can you elaborate? 15-Dec-19 11:11 PM Any given wavelength band you pick off from spectral expansion has fraction of the total power. 15-Dec-19 11:11 PM if your pulse is a broad spectrum, sure 15-Dec-19 11:11 PM which is definitely the case with ti:sapphire, but not necessarily - rarely so - with fiber 15-Dec-19 11:17 PM Your experience with fiber lasers and specific wavelength pick off does not seem consistent with mine. I guessing you have an application I haven't done. 15-Dec-19 11:18 PM I'm not referring to dial-a-wavelength sort of situation with fiber, I think that's where I'm misinterpreting 15-Dec-19 11:18 PM definitely if you're wanting an on-demand pulse of a wavelength of your choosing you're going to be sacrificing a lot of energy that isn't in your desired band 15-Dec-19 11:18 PM I interpreted your earlier sentence as any femto pulse from fiber inherently is going to sacrifice lots of power 15-Dec-19 11:20 PM For a given value of "love", I love the ability to take a fiber laser and get pretty much whatever you want out of it. Every year, that power goes a little bit higher and the versatility improves. From a laser safety perspective, it's infuriating. 15-Dec-19 11:21 PM I can imagine the dial-a-wavelength aspect is particularly infuriating from a safety perspective 15-Dec-19 11:22 PM As I said 20 years ago in the heyday of the MOPOs, "[tosses a pair of coffee mugs at the engineers] That's the best I can do for you. Tell me how you'd like to save yourself from yourself." 15-Dec-19 11:24 PM Hey so we have these devices... they can concentrate enormous energy... spatially and temporally... we want you to make sure they're safe. 15-Dec-19 11:36 PM And a lot of that depends on your cognizance of what you're doing and when. I can buy you a lot of sets of gogs, but it's up to you to wear the right one when. And sometimes its a matter of protecting from the worst thing in a pack of bad things. 15-Dec-19 11:37 PM agreed. In the hobby world you also have the not-so-great environment of family/co-dwellers and pets and whatnot 15-Dec-19 11:37 PM I have a specific power extension/cord/whatever tied in with my lab door and at one point found myself frustrated with the fiance as to how many times things powered down, then realized what I was getting upset about 15-Dec-19 11:39 PM And sometimes you need just a tiny bit of transmission at 532 (or whatever) so you can see what you’re doing for alignment without the temptation to take glasses off 15-Dec-19 11:41 PM I have various cameras with IR filters removed and try to use them as much as possible so I can keep my eyeballs out of the equation entirely, but doesn't work always 15-Dec-19 11:41 PM PROTIP: take out your phone and watch it via your camera. Indirect viewing is wonderful and makes the colorshift for you. 15-Dec-19 11:41 PM it'd be great if InGaAs arrays weren't so darn expensive for the further IR bands 15-Dec-19 11:41 PM ESPECIALLY for 532nm. 15-Dec-19 11:41 PM This was a trick I demonstrated to the CEO of a laser PIV company that blew his goddamn mind. 15-Dec-19 11:45 PM webcams these days are so darn cheap, too, even with direct hdmi output or tied in with the phone sort of stuff so you can use a monitor directly without frustration 15-Dec-19 11:45 PM the without frustration part is key so that you actually use it 15-Dec-19 11:45 PM Yep! $100 of webcams and some software gets you a remote monitoring system we couldn't dream of 20 years ago. 15-Dec-19 11:46 PM at the 1um range a standard webcam with IR filter removed still works beautifully 15-Dec-19 11:46 PM not to mention you can usually adjust the exposure too so even if you COULD see the beam by wavelength, you can keep it super dim and still "see" it 15-Dec-19 11:46 PM and if you're surrounded by extra computers and whatnot you can get by with $15 cameras and a cheapo monitor 15-Dec-19 11:49 PM Have been doing some work with nice Ekspla OPOs lately - lovely dial-a-color from like 16000 to 300 nm 15-Dec-19 11:49 PM Big investment though 15-Dec-19 11:51 PM The full enclosure, alignment power only while open, and lots of remote monitoring (now that it's cheap enough) is the castle approach that the UK has been going with in general. It still demands people taking the time to think about the second order effect of their work, but it is ana amazing improvement. 15-Dec-19 11:52 PM thinking about supercontinuum situations.. never considered the difficulty of eyeball protection in that situation 15-Dec-19 11:53 PM [salutes] Welcome to my workdays most days. 15-Dec-19 11:54 PM the only conceivable approach I can think of is just super low power 15-Dec-19 11:54 PM Which is why I usually ask "Really, are sure you want this open air? Please, think of your data. You'll get better results if you box this up." 15-Dec-19 11:54 PM hehehe 15-Dec-19 11:55 PM I'm not lying. In general, the good laser safety practices I want also lead to better scientific results. A photon that doesn't hit a detector is a wasted photon. That's just as true for x-rays as it is lasers. 15-Dec-19 11:56 PM for sure, it's a good argument/suggestion 15-Dec-19 11:57 PM It always warms the heart when a grad student comes to my office to give me a high five for good data after doing an experimental tweak. 16-Dec-19 04:02 AM Seems safe 16-Dec-19 04:02 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-B8D85.png 16-Dec-19 05:08 AM works great for removing eyeshadow too 16-Dec-19 07:43 AM it's a lot of light, it works for removing all kinds of shadows :P 16-Dec-19 07:43 AM Also if you just want to remove your eyes it also has you covered. 16-Dec-19 07:45 AM One could argue it's best at making shadows 16-Dec-19 07:45 AM my go-to for moon landing deniers btw, no technology back then to make such crisp shadows 16-Dec-19 07:45 AM at least not without turning things ruby red at the same time 16-Dec-19 09:30 AM That's way too technical to explain to those people though... 16-Dec-19 09:34 AM How long until this discord server becomes Laser Hackers? 16-Dec-19 09:38 AM nope 16-Dec-19 10:41 AM The “laser cleaners” are extremely popular in Europe where they have a couple centuries of soot to remove from buildings and statues. They are treated with a similar level of training and worksite controls as a flamethrower. The beams are fairly divergent, much like a FLAMMENWURFER, so you control the work areas for “DO NOT BE HERE” for LASERWURFER work. Also, I am very proud my autocorrect remembered LASERWURFER and FLAMMENWURFER. It’s been a couple years since I’ve used those terms. 16-Dec-19 11:36 AM Well, they are basically giant fiber laser engravers 16-Dec-19 11:36 AM except more dangerous because you move them around while they're running 16-Dec-19 09:17 PM https://www.ebay.com/itm/AMS-Laserscope-Greenlight-HPS-High-Performance-Laser-w-Foot-Switch-13170/254233794410 diode pumped, q-switched(maybe?) and I think 150W? 16-Dec-19 09:17 PM ah, no, not q-switched 16-Dec-19 09:17 PM 120W continuous 532nm DPSS 16-Dec-19 09:17 PM fiber output 16-Dec-19 09:17 PM obviously I can't afford to buy and ship that, but some of you might be close 16-Dec-19 09:17 PM looks like there's quite a few of them on ebay 17-Dec-19 04:10 PM it is Q-switched 17-Dec-19 04:10 PM if it's 532nm 17-Dec-19 04:10 PM it will be Q-switched. 17-Dec-19 04:10 PM especially the laserscope 17-Dec-19 04:13 PM why would it be? 17-Dec-19 04:13 PM you may be confusing q-switching and DPSS 17-Dec-19 04:13 PM it could be pulsed 17-Dec-19 04:20 PM that's how you pulse the laser 17-Dec-19 04:20 PM the frequency doubling crystal works better the higher power pulse that hits it. 17-Dec-19 04:21 PM pulsed as in CW modulation 17-Dec-19 04:21 PM not q switching 17-Dec-19 04:21 PM not really very viable. 17-Dec-19 04:21 PM sure is 17-Dec-19 04:21 PM but I'm not leaving out the possibility that there's a q switch in there too 17-Dec-19 04:22 PM you won't get the peaks you need compared to Q-Switched 17-Dec-19 04:22 PM for the NLC 17-Dec-19 04:22 PM a 120W q-switched DPSS 532 laser would likely have output in the megawatts 17-Dec-19 04:22 PM which would do some fun stuff to skin 17-Dec-19 04:22 PM indeed 17-Dec-19 04:22 PM https://i.imgur.com/cpNArjL.jpg 17-Dec-19 04:22 PM that's mine, non-functional laserscope 17-Dec-19 04:23 PM ah, so you have one 17-Dec-19 04:23 PM that's an AOM right there 17-Dec-19 04:23 PM where's the KTP crystal? 17-Dec-19 04:23 PM I don't quite get the diagram 17-Dec-19 04:24 PM and here is a SUPER Laserscope 17-Dec-19 04:24 PM focusing lens, beam dump, dichroic that goes off to the aiming laser 17-Dec-19 04:24 PM how fast is it pulsed? 17-Dec-19 04:25 PM uuuh, not sure 17-Dec-19 04:25 PM https://i.imgur.com/xxDVYNN.jpg 17-Dec-19 04:25 PM here is my one 17-Dec-19 04:25 PM it's flash lamp powered 17-Dec-19 04:25 PM oh, I thought it was diode pumped 17-Dec-19 04:25 PM my one is flash-lamp 17-Dec-19 04:25 PM but yeah, you won't get the high spike pulses you need to have an efficient KTP frequency doubling without a Q-Switch 17-Dec-19 04:25 PM for tiny, low powers you could get away with it 17-Dec-19 04:25 PM but over a few Watts, really needs to be QSwitched AFAIK 17-Dec-19 04:26 PM yeah, for KTP you'd want a q switch 17-Dec-19 04:27 PM indeed 17-Dec-19 04:27 PM I'd actually take the KTP crystal out for my application 17-Dec-19 04:27 PM since I just need very fast (>10kHz) and very powerful short pulses 17-Dec-19 04:27 PM you'd need to mess around a fair bit with the optics 17-Dec-19 04:27 PM to get the IR out 17-Dec-19 04:27 PM in fact, a major re-design for a laserscope 17-Dec-19 04:27 PM due to the Z-fold shape. 17-Dec-19 04:27 PM if I had the choice I'd just grab the relevant bits, the q switch and its brains, pump diodes 17-Dec-19 04:28 PM it would be a fricking pain 17-Dec-19 04:28 PM make a transmission based laser 17-Dec-19 04:28 PM pump diodes shining straight into the crystal from the back 17-Dec-19 04:28 PM simplest design possible 17-Dec-19 04:28 PM good luck xD 17-Dec-19 04:28 PM good money would be a better wish 17-Dec-19 04:28 PM sadly we've deduced with Mason that it'd cost around the same amount of money, but a ton more effort, to build a DIY DPSS q-switched laser, than to buy a pre-built fiber one 17-Dec-19 04:29 PM mason? 17-Dec-19 04:29 PM @ Mason_Yu 17-Dec-19 04:29 PM just scroll up, we discussed the practicality of this yesterday 17-Dec-19 04:30 PM https://www.aliexpress.com/wholesale?catId=0&initiative_id=SB_20191217162952&SearchText=YAG+laser+diode 17-Dec-19 04:30 PM this would be your best bet 17-Dec-19 04:30 PM oh huh 17-Dec-19 04:30 PM they're... just... a thing 17-Dec-19 04:30 PM @Mason_Yu pinging 17-Dec-19 04:30 PM is this just... a laser pump? 17-Dec-19 04:30 PM or a laser-pumped... rod? 17-Dec-19 04:33 PM laser diode pump 17-Dec-19 04:33 PM and rod. 17-Dec-19 04:33 PM no mirrors 17-Dec-19 04:35 PM so in theory all that's needed is two mirrors, one transmissive, and a q-switch? 17-Dec-19 04:35 PM well and the drivers of course 17-Dec-19 04:35 PM yah 17-Dec-19 04:35 PM also, poke your head over here: 17-Dec-19 04:35 PM https://www.youtube.com/user/w0003947/videos?disable_polymer=1 17-Dec-19 04:35 PM I did 17-Dec-19 04:35 PM I was unsure what he used 17-Dec-19 04:37 PM https://www.youtube.com/watch?v=s9uCANj7XZ8 17-Dec-19 04:37 PM Buying pump diodes from China may not be chepaer than eBay 17-Dec-19 04:37 PM looks like the one on alibaba 17-Dec-19 04:37 PM depends 17-Dec-19 04:37 PM @Mason_Yu eBay is like 10x cheaper 17-Dec-19 04:37 PM speak to the factory directly. 17-Dec-19 04:37 PM you can get similar heads for $200 17-Dec-19 04:37 PM in unknown condition 17-Dec-19 04:37 PM oh? 17-Dec-19 04:37 PM yeah 17-Dec-19 04:37 PM but as Mason has the power to communicate with factories in Chinese, he might get some super favorable prices too 17-Dec-19 04:38 PM It's finals week for me lol, I'll call a few factories as soon as I'm done with exams 17-Dec-19 04:38 PM good luck with the finals haha 17-Dec-19 04:39 PM https://www.ebay.co.uk/itm/YAG-Laser-Trumpf-Haas-HL-4406-D-HL4406D-2007-complete/264172778531?hash=item3d81ecb423%3Ag%3AzWoAAOSwSfJcUvRV&LH_ItemCondition=4 17-Dec-19 04:39 PM group funded teardown? 17-Dec-19 04:39 PM I was about to say that lol 17-Dec-19 04:39 PM all it is is just racks upon racks of FAP assemblies 17-Dec-19 04:39 PM and some beam combining optics 17-Dec-19 04:40 PM https://www.ebay.co.uk/itm/YAG-Laser-Trumpf-Haas-Laser-HL-1006-D-Collection-Only/352843640342?hash=item52271eae16%3Ag%3AqKAAAOSwTsNdCkUn&LH_ItemCondition=4 17-Dec-19 04:40 PM oh daym 17-Dec-19 04:40 PM tens and tens of FAP assemblies 17-Dec-19 04:40 PM if they're lower power, hundreds of them 17-Dec-19 04:40 PM xD 17-Dec-19 04:40 PM FAP FAP FAP FAP 17-Dec-19 04:41 PM https://www.ebay.com/itm/CEO-YAG-RB-64688-Diode-Pumped-Nd-YAG-Rod-Laser-Module-64688-7000-hours-used/262093141354 17-Dec-19 04:41 PM huh 17-Dec-19 04:41 PM given that there's 31 sold... I'm going to hazard a guess they're still functional 17-Dec-19 04:41 PM that kind of thing never shows for me 17-Dec-19 04:42 PM use ebay.com 17-Dec-19 04:42 PM sort by price: highest first 17-Dec-19 04:42 PM ;) 17-Dec-19 04:42 PM always used .co.uk 17-Dec-19 04:42 PM yeah, local versions show less 17-Dec-19 04:42 PM also, since you're in the UK.. 17-Dec-19 04:42 PM I'll PM you about an interesting thing 17-Dec-19 05:24 PM @Metanoic you're the optical guy here 17-Dec-19 05:24 PM Tell us, what's the catch? 17-Dec-19 05:24 PM Why are these Nd:YAG pumps so cheap on eBay, and why q-switching them is some kind of trap we don't know about 17-Dec-19 05:24 PM Or maybe they're just less known and aren't actually traps? 17-Dec-19 05:24 PM 40 watt pump, straight into two mirrors with a q-switch 17-Dec-19 05:24 PM surely there's SOMETHING wrong 17-Dec-19 05:24 PM found the supplier of the modules on ebay 17-Dec-19 05:24 PM https://detail.1688.com/offer/521390697151.html?_server_name=www.xytlaser.cn&visitorIp=178.127.103.227&_server_port=80&from_site=officialsite&spm=a262gm.8761431.0.0.17ba41dck9Qd9V 17-Dec-19 05:24 PM https://i.spirit.re/NTkA3.png 17-Dec-19 05:24 PM Gucci q-switches, too, of course. 17-Dec-19 05:24 PM (it's Gooch & Housego) 17-Dec-19 05:24 PM looks like brand new they cost around $500-700 17-Dec-19 05:35 PM This is an opportunity to investigate 17-Dec-19 05:35 PM I think it's unlikely we can build something cheaper with brand new stuff, but there is a used market in China as well 17-Dec-19 05:36 PM But the power 17-Dec-19 05:36 PM These are 50W modules 17-Dec-19 05:36 PM a 50W fiber laser is what, $12k? 17-Dec-19 05:36 PM No, more like $3k 17-Dec-19 05:36 PM Perhaps even less actually 17-Dec-19 05:36 PM yeah, closer to 3-4k 17-Dec-19 05:36 PM but still, 3x cheaper is worst case scenario 17-Dec-19 05:36 PM but looks like these discrete air cavity lasers have much higher output energy and much shorter pulses 17-Dec-19 05:36 PM everything I've seen is <30ns and >2mJ 17-Dec-19 05:36 PM at 10kHz ish 17-Dec-19 05:36 PM and yeah, I'd totally buy all this stuff used 17-Dec-19 05:36 PM not to mention you can just open the q switch continuously(with cooling?) and turn it into one hell of a laser cutter 17-Dec-19 05:48 PM Looks to me like somebody just got wise to the DIY market, combined with the DIY market thriving, and just came up with a sensible package. 17-Dec-19 05:49 PM That's the thing - I have never seen these red DPSS modules used in DIY projects 17-Dec-19 05:49 PM That Daniel Beam guy is the only one I've seen who did 17-Dec-19 05:49 PM well, and rocketman340 but he's a grumpy guy working in a lab 17-Dec-19 05:49 PM But there's a big enough market that there's companies buying them for $700 a piece 17-Dec-19 05:51 PM It's going to be $470 a piece for the 50W red module 17-Dec-19 05:51 PM 50W is huge but it's very good to know that this is an option. 17-Dec-19 05:52 PM When beam combining dont forget about destructive interference. 17-Dec-19 05:52 PM I think there's got to be a catch somewhere? I couldn't find super detailed info on these beyond some adversizing that's often inconsistent 17-Dec-19 05:52 PM There's no beam combining necessary at these powers 17-Dec-19 05:52 PM Was referring to the rack of FAP stuff earlier 17-Dec-19 05:52 PM Processing the backlog 17-Dec-19 05:53 PM We're thinking of just this: [100% mirror] --- [Module] --- [Q-switch] --- [Output mirror] --- [Glass] --- [galvos/etc] 17-Dec-19 05:53 PM Is there a catch to this? 17-Dec-19 05:54 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/T1W7W_XcVnXXb9JTE8_101726-C70DC.png 17-Dec-19 05:54 PM yes, almost exactly that actually 17-Dec-19 05:54 PM with slightly more ghetto mirror mounts 17-Dec-19 05:55 PM Q-switch should be from eBay, more expensive from China when factoring in shipping and controller cost 17-Dec-19 05:55 PM yup 17-Dec-19 05:55 PM this setup would also make a quasi-continuous laser possible 17-Dec-19 05:55 PM 50% duty cycle q switch driving 17-Dec-19 05:55 PM The modules take chilled water, but that's not a big issue 17-Dec-19 05:55 PM Hmm, is the q-switch rated for this? 17-Dec-19 05:56 PM yes 17-Dec-19 05:56 PM not sure about funky driving modes, but the power rating certainly 17-Dec-19 05:56 PM they also need chilling 17-Dec-19 05:56 PM Well the a qswitch needs to be in the resonator, looks like those diode pump + rod packages are self contained 17-Dec-19 05:57 PM yes, that's the allure of this thing 17-Dec-19 05:57 PM Yep, these are side-pumped Nd:YAG crystal modules 17-Dec-19 05:57 PM no need to make weird cavity mirrors, you get a self contained DC-powered rod 17-Dec-19 05:57 PM for less than the combined price of the two as well 17-Dec-19 05:57 PM (when bought used) 17-Dec-19 05:58 PM Are they advertising these as merely a diode pumped rod and no resonator? 17-Dec-19 05:58 PM yes 17-Dec-19 05:58 PM Ah 17-Dec-19 05:58 PM I'm wondering what kind of output we would see though 17-Dec-19 05:58 PM in terms of pulse length, energy 17-Dec-19 05:59 PM Can't say for certain, but I think it's likely cost effective 17-Dec-19 05:59 PM any idea of the range at all? 17-Dec-19 06:01 PM It's difficult to say. Need to know pump wavelength to know absorption, and hard to put a figure on just stimulated emission 17-Dec-19 06:01 PM One adversized optical set-up 17-Dec-19 06:01 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/HTB1389KbMaH3KVjSZFpq6zhKpXaY-F408E.png 17-Dec-19 06:01 PM well, since it's Nd:YAG, I'm going to say it's just a couple 808 diode bar arrays stacked up to the yag rod 17-Dec-19 06:01 PM Yep, surrounding it radially cooled by one water jacket 17-Dec-19 06:02 PM harf refrect mirror and red raser 17-Dec-19 06:02 PM I would expect substantial output, no reason not to 17-Dec-19 06:02 PM what about pulse lengths? 17-Dec-19 06:02 PM are we going to see single-double digit nanoseconds, or way into the micros? 17-Dec-19 06:03 PM That's going to be up to the mode locking method and actual mode locker 17-Dec-19 06:03 PM Can you explain how that works? 17-Dec-19 06:03 PM All I see is an AOM driver that outputs RF gated by a TTL signal 17-Dec-19 06:03 PM Something like a saturable absorber will be very high rep rate short pulses - assuming good recovery 17-Dec-19 06:04 PM I don't need very high repetition rates, double or triple digit kHz is totally fine 17-Dec-19 06:04 PM which most drivers can do 17-Dec-19 06:05 PM Then you have active quality switching which will depend on the mechanism again, e.g PZT vs lithium niobate or similar with much faster piezo effects 17-Dec-19 06:05 PM the most available q-switches are Gooch & Housego QS27 series 17-Dec-19 06:05 PM Your pulse length will be derived from the qswitch 17-Dec-19 06:05 PM That statement stands on it's own for a single pulse 17-Dec-19 06:05 PM which spec of the q switch defines the pulse length? 17-Dec-19 06:06 PM When you want subsequent you must have a gain medium actively lasing so then you toss in pump power and gain efficiency to the mix 17-Dec-19 06:07 PM looks like all the affordable switches are fused silica 17-Dec-19 06:07 PM Then assuming that's all good then you're on to how quick the mode locker can recover and go again 17-Dec-19 06:07 PM that's the only thing I can see here in the datasheets 17-Dec-19 06:07 PM https://i.spirit.re/jc17R.png 17-Dec-19 06:09 PM I would expect the arrangement to be on par with "conventional" dpss, I can't think of any glaring reason why the numbers wouldn't be extremely similar 17-Dec-19 06:09 PM they're made for DPSS 17-Dec-19 06:10 PM Like I said, I dont see any reason to suspect a gimmick or gotcha. 17-Dec-19 06:10 PM Aside from our collective... racism or whatever you want to call the "China cheap" idea 17-Dec-19 06:11 PM The driver specified a pulse width adjustment range from 1 to 14 microseconds 17-Dec-19 06:11 PM that's not good for us 17-Dec-19 06:11 PM (not calling it racist, just dont know what to actually call it lol) 17-Dec-19 06:12 PM https://i.spirit.re/bm0ct.png 17-Dec-19 06:12 PM There's a G&HG q switch chart 17-Dec-19 06:12 PM Specifies the material too 17-Dec-19 06:12 PM or... at least it should 17-Dec-19 06:12 PM most ebay ones don't follow the same code 17-Dec-19 06:12 PM But assuming the switch itself is compatible, can it be driven at the nanosecond range? 17-Dec-19 06:14 PM Sry out in the shop on my phone so distracted and such 17-Dec-19 06:14 PM Take your time 17-Dec-19 06:14 PM Or maybe the q-switch driver times don't match the actual pulse lengths? 17-Dec-19 06:14 PM Maybe 14us of the driver is... 200ns of the output, or something 17-Dec-19 06:16 PM The mode locker will be the speed limit for something with e.g. 50W of 808nm diode pumping. Unless they tossed in a ridiculously too large rod or something stupid like that. 17-Dec-19 06:16 PM Looks like the rods are around 3mm in diameter 17-Dec-19 06:16 PM 170 mm long or so 17-Dec-19 06:17 PM that's wrong 17-Dec-19 06:17 PM can't be 170, that's huge 17-Dec-19 06:17 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/2401187067_91973921-71BAA.jpg 17-Dec-19 06:17 PM 3mm in diameter, 65mm long 17-Dec-19 06:17 PM Sorry, yeah it's 65 or 70 17-Dec-19 06:17 PM There's two versions one with a slightly longer rod for some reason 17-Dec-19 06:18 PM higher power probably 17-Dec-19 06:18 PM Same 50 W rated power 17-Dec-19 06:19 PM There's a bunch of pumps that cost $250, some a bit less 17-Dec-19 06:19 PM Another $250 on the q-switch 17-Dec-19 06:19 PM not bad 17-Dec-19 06:19 PM but not good either 17-Dec-19 06:19 PM Longer rod will give higher output but push the repetition rate lower bounds upwards 17-Dec-19 06:19 PM Maybe meant for use with output mirrors that has different transmission rates? 17-Dec-19 06:19 PM If that made any sense 17-Dec-19 06:19 PM that makes sense 17-Dec-19 06:19 PM So my only concern now is the pulse length 17-Dec-19 06:19 PM microsecond range pulses are unacceptable for machining anything, only good for marking and burning stuff 17-Dec-19 06:20 PM Too long a rod will give you a big nothing if taken to extremes, and bad efficiency when still "in the ballpark" 17-Dec-19 06:20 PM I trust that the engineer did his job properly 17-Dec-19 06:20 PM so the question isn't if there's any limits to the pulse length range 17-Dec-19 06:20 PM but rather what the pulse length will be 17-Dec-19 06:20 PM if the driver says is can drive the q switch with microsecond pulses, does this mean we're going to get microsecond pulse lengths on the output? 17-Dec-19 06:21 PM You need both pulse length and rep rate to really judge 17-Dec-19 06:21 PM rep rate is around 10khz on most drivers 17-Dec-19 06:22 PM I would compare to existing systems as if apples and apples and derive your estimates from that 17-Dec-19 06:22 PM existing systems don't seem to use these 17-Dec-19 06:23 PM Same thing different package/product 17-Dec-19 06:25 PM hmm 17-Dec-19 06:26 PM Do they spec any spectral range or transverse beam mode? 17-Dec-19 06:26 PM looks like they're all 1064 17-Dec-19 06:26 PM no mode I can see 17-Dec-19 06:26 PM Then for-sure multimode otherwise they'd brag 17-Dec-19 06:27 PM Is that good or bad? 17-Dec-19 06:27 PM Bad on both fronts, longitudinal multimode means not monochrome, transverse multimode means non-gaussian beam profile 17-Dec-19 06:27 PM Then again that's a whole package situation too 17-Dec-19 06:27 PM Hard to judge like I said, e.g. it's up to you to make your resonator length a length that has less combinations of sustainable wavelengths 17-Dec-19 06:29 PM So the distance between mirrors is also critical, right? 17-Dec-19 06:29 PM Or is it more of a "slide it around until best results" kind of thing? 17-Dec-19 06:30 PM Beam profile stems from the gain medium so that part is a bit ehhhh in not spec'ing 17-Dec-19 06:30 PM Yea, lemme hop to comp real quick 17-Dec-19 06:30 PM okay, so as far as longitudinal modes go, you're familiar with constructive and destructive interference right? 17-Dec-19 06:31 PM I'm familiar with interference but not modes 17-Dec-19 06:31 PM well with longitudinal mode it's all about interference 17-Dec-19 06:31 PM imagine it as it sounds, firstly.. longitudinal as in along the length of the resonator 17-Dec-19 06:31 PM so let's say you had a pool of water, 100 meters long and we made some waves starting at one end at 10hz 17-Dec-19 06:33 PM right, that's basic interference 17-Dec-19 06:33 PM so imagine when the wave hits the end of the pool and comes back to the waves still propagating 17-Dec-19 06:33 PM if you make the length of your pool precise, and the frequency of your waves precise, you can determine what length of pool will guarantee the waves coming back will constructively interfere 17-Dec-19 06:34 PM So the ideal resonator length should be a multiple of 1064, right? 17-Dec-19 06:34 PM as close as possible to it 17-Dec-19 06:34 PM basically, yes 17-Dec-19 06:35 PM well, that's a "whack it with a mallet until it's bright" situation 17-Dec-19 06:35 PM but if you've ever seen a high dollar wavemeter you know there's a lot of numbers after the decimal in 1064 17-Dec-19 06:35 PM whack it with... thoughts? 17-Dec-19 06:36 PM well my preferred method is measure while tuning lol 17-Dec-19 06:36 PM output power? 17-Dec-19 06:36 PM spectral output 17-Dec-19 06:36 PM heh, I don't have a spectrometer that precise 17-Dec-19 06:36 PM or one at all 17-Dec-19 06:37 PM well, with enough energy you can use second order nonlinearity effects to make it measure itself 17-Dec-19 06:37 PM (just a fancy way of saying high harmonic generator or similar non-linear optical phonomena) 17-Dec-19 06:38 PM how would this affect pulse length? 17-Dec-19 06:39 PM longitudinal mode won't, but it will effect the ... effect of the output on whatever it hits 17-Dec-19 06:39 PM quanta and photoelectric effect and whatnot 17-Dec-19 06:41 PM so what makes the nanosecond and picosecond pulse lengths? 17-Dec-19 06:41 PM I'm assuming it's not just how quickly you pulse the q switch 17-Dec-19 06:42 PM how quickly you can trigger a population inversion, resulting in stimulated emission 17-Dec-19 06:43 PM isn't that PRR? 17-Dec-19 06:43 PM it definitely ties in, but rep rate is the ensemble of multiple factors 17-Dec-19 06:44 PM the Q switch acts as a mirror sitting in front of the half transparent mirror 17-Dec-19 06:44 PM when driven it becomes transparent 17-Dec-19 06:44 PM actually, that's wrong, isn't it 17-Dec-19 06:44 PM q switches modulate the loss in the resonator 17-Dec-19 06:47 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-EF463.png 17-Dec-19 06:47 PM no it's close enough - there are more ways than that, but I trust that the qswitch you're dealing with effectively acts that way 17-Dec-19 06:47 PM it would act as a mirror? 17-Dec-19 06:48 PM not realllly but in effect it's a fine logical analogy 17-Dec-19 06:48 PM Wouldn't it cause the laser to... lase, when it's turned off as well? 17-Dec-19 06:48 PM at the low(ish) pump power level 17-Dec-19 06:49 PM most often I would think frustrated internal reflection is the underlying method but either way 17-Dec-19 06:49 PM so it would reflect more chaotically, not like a mirror 17-Dec-19 06:51 PM so back to that longitudinal mode stuff from earlier 17-Dec-19 06:51 PM let's say that I took a section of the pool, about 5 feet long, and wrapped it in a big plastic bag, totally water tight 17-Dec-19 06:51 PM for any waves going through that region, they'd make the water next to it move just the same 17-Dec-19 06:51 PM but now consider I momentarily drug that bag 2 feet forward then drug it right back to where it was 17-Dec-19 06:51 PM it'd totally momentarily cause some serious interference issues downstream 17-Dec-19 06:52 PM the bag analogy is the q switch, right? 17-Dec-19 06:52 PM an AOM, yes 17-Dec-19 06:52 PM brb wife let the cat out 17-Dec-19 06:53 PM alright 17-Dec-19 06:53 PM Please correct me if I'm wrong, but it appears that the pulse width of a q-switched laser is mostly dependent on how fast the gain medium can be saturated with the pump power and with a given resonant cavity, and the 1 - 14 microsecond pulse length for the q-switch does not play a direct role unless saturation takes much longer than that, in which case two pulses may form 17-Dec-19 06:56 PM I think I'm coming to the same conclusion 17-Dec-19 06:56 PM There's many caveats here, for example the rise/fall time of the AOM 17-Dec-19 06:57 PM I think those relate to the RF drive power 17-Dec-19 06:58 PM It's like ~100ns for the ones we're looking at. If it interferes with the pumping of the gain medium it could cause all sorts of interference in the resonant cavity right? 17-Dec-19 06:58 PM let's see what he has to say about it 17-Dec-19 07:03 PM back 17-Dec-19 07:03 PM In the meantime @Mason_Yu can you figure out what the third gray wire is? 17-Dec-19 07:03 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/s-l1600-76702.png 17-Dec-19 07:03 PM That's the 75W module I believe 17-Dec-19 07:03 PM same with the 50 17-Dec-19 07:03 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/O1CN01AJjJsE1qrUHViXziI_3455295549-0799A.png 17-Dec-19 07:04 PM I'm not going to buy new, they're way too expensive new to be worth it 17-Dec-19 07:04 PM That's the 50W one with 70 mm long crystal 17-Dec-19 07:04 PM Okay, let me look 17-Dec-19 07:04 PM they're $200 on eBay, these and another one from Germany 17-Dec-19 07:04 PM that one has two wires 17-Dec-19 07:09 PM It's probably a built-in thermistor 17-Dec-19 07:09 PM Some sort of temperature monitoring line 17-Dec-19 07:09 PM with a super thick cable? 17-Dec-19 07:10 PM That doesn't make much sense, but I could find instruction to connect a temperature monitoring line to the dedicated power supply 17-Dec-19 07:11 PM well, not to worry, I found a super similar one to the one you sent 17-Dec-19 07:11 PM having difficulty making coherent words lol 17-Dec-19 07:11 PM except it doesn't have those black caps and the housing is black 17-Dec-19 07:11 PM 18V @ 18A 17-Dec-19 07:11 PM with a puny 6A lasing current 17-Dec-19 07:11 PM :D 17-Dec-19 07:12 PM so, yes - the root pulses are a result of the resonator itself and the gain medium and whatnot, but when you throw in something like an aom you're messing with the way those same pulses evolve 17-Dec-19 07:13 PM Okay, is there a way to calculate this? Given a pumping power, cavity length, gain medium and AOM characteristic? 17-Dec-19 07:13 PM @Deleted User Those are actually made by a different manufactuer, the newer ones are all just two lead devices 17-Dec-19 07:14 PM I'm eyeing this one 17-Dec-19 07:14 PM https://www.ebay.com/itm/Laser-Module-Model-GTPC-50S/254349998315 17-Dec-19 07:20 PM https://www.ebay.com/itm/Diode-Pump-Laser-Module-Model-DPL-5040B/254376593635 17-Dec-19 07:20 PM Well I'm calling dips on this one then 17-Dec-19 07:20 PM best if we have the same module 17-Dec-19 07:20 PM that seller has 2 17-Dec-19 07:20 PM I messaged him to see if he offers tracked shipping 17-Dec-19 07:21 PM They are actually made by the same manufacturer too, I got confused with a reseller 17-Dec-19 07:21 PM I should call the factory 17-Dec-19 07:21 PM Get more details 17-Dec-19 07:21 PM but my biggest concerns are: 1) unprotected rod damage 2) THEY ARE ALL UNSHORTED 17-Dec-19 07:21 PM so it's a total gamble if we're getting an oversized yag rod with a bunch of dead PN junctions 17-Dec-19 07:21 PM or an actual DPSS head 17-Dec-19 07:23 PM According to the advertisement they have anti-static protection inside 17-Dec-19 07:23 PM huh, that's something I couldn't find in english 17-Dec-19 07:24 PM At least the DPL ones have that 17-Dec-19 07:24 PM I'm going to call and see what's the difference 17-Dec-19 07:25 PM ask for the factory prices too, just in case :P 17-Dec-19 07:25 PM yes you can calculate out all the details and model things and whatnot, definitely would not be a direct task if factoring in all the pieces 17-Dec-19 07:26 PM It's ~$520 on their website, doubt they'll give a discount 17-Dec-19 07:26 PM my next concern is optics 17-Dec-19 07:26 PM even interpreting the result after changing various parameters would be difficult 17-Dec-19 07:26 PM mirrors, mounts, etc 17-Dec-19 07:26 PM Hmm, okay, I am pretty confident that the pulse length is not going to be in the microseconds though 17-Dec-19 07:27 PM anything between 0 and 100ns is fine by me 17-Dec-19 07:27 PM e.g. are we using an AOM to create a standing wave versus muddying things up temporarily like a q-switch 17-Dec-19 07:27 PM they're all AOMs 17-Dec-19 07:27 PM fused silica with 24-27MHz RF input 17-Dec-19 07:27 PM at 10-100W 17-Dec-19 07:27 PM AOMs take on many a tasks though, mind you 17-Dec-19 07:28 PM any details to be aware of? 17-Dec-19 07:28 PM drive it like a qswitch if you want qswitching, I guess? 17-Dec-19 07:29 PM anything specific in there? 17-Dec-19 07:29 PM the drivers just usually output RF and accept a TTL and sometimes analog modulation level 17-Dec-19 07:30 PM should be peachy then 17-Dec-19 07:30 PM factor in pulse duration on the order what you see in other q-switched applications, no reason to suspect you'd get different results 17-Dec-19 07:30 PM in this case the AOM is making /sure/ the gain medium is saturated then unleashing hell 17-Dec-19 07:36 PM so just a moderate PRR? 17-Dec-19 07:36 PM should be able to trade off length for rep rate so long as the gain medium is getting pumped well enough 17-Dec-19 07:37 PM are we talking orders of magnitude here? 17-Dec-19 07:39 PM asking the wrong question I think.. 17-Dec-19 07:39 PM or at least I'm thinking in circles 17-Dec-19 07:39 PM I mean orders of magnitude PRR difference 17-Dec-19 07:39 PM well you could for-sure go slower by orders of magnitude, as many orders as you have patience 17-Dec-19 07:40 PM I mean what's the window for pulse height 17-Dec-19 07:40 PM Are we talking 100hz vs 10khz here 17-Dec-19 07:40 PM or 10khz vs 500khz 17-Dec-19 07:40 PM what does the q-switch doc say? How fast can it modulate? 17-Dec-19 07:41 PM the doc says nothing 17-Dec-19 07:41 PM well that's helpful 17-Dec-19 07:42 PM assuming it can switch as fast as possible, does this depend on the pumping power as well? 17-Dec-19 07:42 PM logically, this is what's happening: 17-Dec-19 07:42 PM uuuugh 17-Dec-19 07:44 PM oh no 17-Dec-19 07:45 PM used a curse word and it erased my message 17-Dec-19 07:45 PM pump diodes energize rod, begins inverting population getting rod all excited, q-switch is like "lol gonna make really bad resonator for a while", rod keeps getting pumped but no stimulated emission because q-switch doesn't let any light bounce back and forth, q-switch is like "ok party", rod blows its top, q-switch goes back to "lol bad resonator", rod starts getting energized again, rinse and repeat 17-Dec-19 07:45 PM so the speed limits in that process are a) how quickly can we create a population inversion in the rod and b) how fast can the q-switch go from party-time to poopy-resonator and back 17-Dec-19 07:51 PM But the pulse length is mainly determined by the amount of energy for the rod to have stimulated emission right? And the delay of the pulse from the q-switch triggering is dependent on how many resonant cycles it takes for stimulated emission to be dominant and exponentially rising 17-Dec-19 07:51 PM Am I understanding that part correctly? 17-Dec-19 07:57 PM trying to find a good reference on the SE portion 17-Dec-19 07:58 PM Thanks for helping us out! 17-Dec-19 07:58 PM That was very helpful 17-Dec-19 07:58 PM So the next order of business - finding the optics to go with this @Mason_Yu 17-Dec-19 07:58 PM I found a ton of stuff from China 17-Dec-19 07:59 PM I found sources for affordablish and suitable q switches(in quantity) and we have two identical laser lots 17-Dec-19 07:59 PM ultimately it's going to come down to a given gain medium and its tendency to absorb or emit, not finding anything exceptional as far as tying in the resonator 17-Dec-19 07:59 PM We need: 1) Optics 2) Driver for the q switch 3) A variable 20V 20A-ish CC supply 17-Dec-19 07:59 PM and that's... it 17-Dec-19 07:59 PM We'll need 1 full reflection mirror, one output mirror, one expander, likely optical mounts to go with all of it 17-Dec-19 08:00 PM OH. 17-Dec-19 08:00 PM Unless you already have this stuff of course 17-Dec-19 08:00 PM goggles. 17-Dec-19 08:00 PM Yep 17-Dec-19 08:00 PM we're dealing with eye-deleting powers here 17-Dec-19 08:00 PM so goggles are a must 17-Dec-19 08:02 PM A combiner for a red laser too on top. Plus the galvo, plus the f-theta lens 17-Dec-19 08:02 PM cheap webcam and remove IR filter for visualizing the beam 17-Dec-19 08:02 PM let's ignore those @Mason_Yu 17-Dec-19 08:02 PM the goal is to make a little spark fountain come out of a metal piece 17-Dec-19 08:02 PM Just build the laser and blast stuff first？ 17-Dec-19 08:02 PM yeah 17-Dec-19 08:02 PM I have no problem with that 17-Dec-19 08:02 PM once the laser is built, we can bolt whatever we want onto it 17-Dec-19 08:02 PM so I guess we can build out a price list 17-Dec-19 08:02 PM or part list in general 17-Dec-19 08:02 PM for a 3mm rod, we want a 4mm q switch 17-Dec-19 08:02 PM https://www.ebay.com/itm/I-QS027-4S4G-U5-ST1-GOOCH-HOUSEGO-ACOUSTO-OPTICS-I-QS027-4S4G-U5-ST1/254186828064 17-Dec-19 08:02 PM buying 2 is a lot cheaper, so I guess I can order both and ship one to you 17-Dec-19 08:05 PM Okay 17-Dec-19 08:06 PM the Stallion is more robust and faster 17-Dec-19 08:06 PM so that's an advantage 17-Dec-19 08:06 PM but the disadvantage is that it's 27MHz 17-Dec-19 08:06 PM fewer driver choices 17-Dec-19 08:07 PM Driver I can buy on my own: 17-Dec-19 08:07 PM https://www.ebay.com/itm/GOOCH-HOUSEGO-R38027-50DMPK-PL1-A-MOTOR-DRIVE/283489288241 17-Dec-19 08:07 PM buuuuut I can't 17-Dec-19 08:07 PM only one of those available 17-Dec-19 08:07 PM :< 17-Dec-19 08:07 PM https://www.ebay.com/itm/GOOCH-HOUSEGO-R39027-50DMFPS-A-DRIVER/264274821673?hash=item3d8801c229:g:qBMAAOSwsO1cq4GC 17-Dec-19 08:07 PM More expensive one 17-Dec-19 08:08 PM what's the difference? 17-Dec-19 08:08 PM https://www.ebay.com/itm/Neos-Driver-N38027-50DMPK-Gooch-Housego-LASER-optic-RF-Driver/333380458046? 17-Dec-19 08:09 PM $70 to ship :< 17-Dec-19 08:10 PM I just checked my bank balance 17-Dec-19 08:10 PM And I have bad news 17-Dec-19 08:10 PM It says "no"? 17-Dec-19 08:10 PM Very much no at the moment 17-Dec-19 08:10 PM Depositing a paycheck this Friday but it's not gonna help much 17-Dec-19 08:10 PM Well, feel free to get the cheaper unit, shipping is expensive for you afterall 17-Dec-19 08:12 PM I think that's the best choice 17-Dec-19 08:12 PM But I'm uncertain about the other optics 17-Dec-19 08:25 PM A short list of optics: 1 DPSS Laser Module: $200 Q-switch QS027-4S4G: $176 Q-switch Driver: ~$60-$140 1 focus lens ~$20 (for testing) 1 full reflection mirror ~$25 1 output coupler 20% transmission ~$25 3 adjustable optical mounts ~$28*3 1 mount for Q-switch ~$25 (optional) Mounting rail and hardware: ~$20 For cutting/engraving: 1 four-times expander: ~$25 1 red laser: $5 RC1001 galvo: ~$140 w/ $110 SAM-USC-1 Control Card f-theta lens 160mm focal length: ~$30 Goggles: $160? 17-Dec-19 08:28 PM oh that's quite affordable 17-Dec-19 08:28 PM are you sure we need 50%? 17-Dec-19 08:29 PM It can be 20% as well 17-Dec-19 08:29 PM This is something I still need more info on 17-Dec-19 08:29 PM earth to @Metanoic 17-Dec-19 08:29 PM how much reflection do we need on the output? 17-Dec-19 08:35 PM I found a description that specified output mirror transmission rate is 20%, let's go with that for now 17-Dec-19 08:35 PM With a resonant cavity length of 170mm 17-Dec-19 08:35 PM That's where the 170 came from! I knew it was from somewhere 17-Dec-19 08:35 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-F8C63.png 17-Dec-19 08:36 PM Should try multiple. I was gonna throw out "15ish" 17-Dec-19 08:37 PM yeah, let's go with 20% then 17-Dec-19 08:37 PM If researching try the term "output coupler" 17-Dec-19 08:58 PM @Mason_Yu goggles are $60-70ish for a questionable Chinese OD7+ pair with CE certs 17-Dec-19 08:58 PM not going to mention those without CE certs at all 17-Dec-19 08:58 PM a good proper pair is $160 17-Dec-19 08:58 PM DO NOT USE WITHOUT TESTING 17-Dec-19 08:58 PM here comes funranium 17-Dec-19 08:58 PM I was just about to say lol 17-Dec-19 08:58 PM it me 17-Dec-19 08:58 PM hey look I did say they're CE certified 17-Dec-19 08:58 PM similar pairs without CE certs are half the price 17-Dec-19 08:58 PM (wonder why lol) 17-Dec-19 08:58 PM but eyes are worth $30 extra 17-Dec-19 08:59 PM No, it's CE marked. That doesn't mean certified from China. Deeply damaged trust is deeply damaged. 17-Dec-19 09:00 PM certified too apparently 17-Dec-19 09:00 PM it's the company everyone keeps recommending, EagleView/Eagle Pair 17-Dec-19 09:00 PM http://www.eaglelaser.cn/En/GoodsView/719.html 17-Dec-19 09:00 PM http://www.eaglelaser.cn/En/GoodsView/847.html 17-Dec-19 09:00 PM looks like they're compliant and certified? 17-Dec-19 09:00 PM I don't know how true it is 17-Dec-19 09:03 PM Oh, these. If you're paying less than $100, do not trust, test to verify. The coatings are, to be kind, variable. Also, these gogs are f'n uncomfortable and delicate. 17-Dec-19 09:04 PM @Mason_Yu so... halfsies for a for-serious pair, each gets one eye? :D 17-Dec-19 09:04 PM I don't like wearing an eyepatch lol 17-Dec-19 09:04 PM well, the serious goggles are ~$160ish 17-Dec-19 09:05 PM Do you have a power meter? 17-Dec-19 09:05 PM no, but I can build one that I wouldn't trust with my eyesight 17-Dec-19 09:05 PM I don't think this kind of thing can be measure with a thermoelectric one, you'd need photoelectric, right? 17-Dec-19 09:05 PM to make sure the power that gets to your looking balls doesn't exceed class 1 levels 17-Dec-19 09:06 PM PE & wavelength dependent ideally. 17-Dec-19 09:07 PM I was thinking of something like a naked solar cell in a black box with a sensitive meter 17-Dec-19 09:07 PM only issue is that I'm not sure I can calibrate it well 17-Dec-19 09:08 PM TOTALLY NEW DIY PROJECT! 17-Dec-19 09:08 PM https://www.ebay.com/itm/Ophir-Laser-Power-Meter-Nova-Display-W-BC20-3W-SH-BC20-3WL-photodiode-sensor/323762545451? 17-Dec-19 09:08 PM only a grand 17-Dec-19 09:08 PM can get a bunch to give out as candy 17-Dec-19 09:11 PM GENTEC has nice things. They are not cheaper, unfortunately. 17-Dec-19 09:11 PM I'm pretty certain I can build a very sensitive and quite linear LPM 17-Dec-19 09:11 PM but I don't have access to a facility where I can calibrate it with an actual laser 17-Dec-19 09:11 PM I suppose an LED would work as well 17-Dec-19 09:12 PM Surplus Melles-Griot HeNe lasers are cheap, stable, and plentiful on ebay. 17-Dec-19 09:13 PM but do they output the same as the tin says? 17-Dec-19 09:13 PM It takes work to kill one of those. Also, ThorLabs alignment lasers are small cheap, and reliable. 17-Dec-19 09:13 PM I don't mean kill 17-Dec-19 09:13 PM I mean output degradation 17-Dec-19 09:14 PM Melles-Griot? Generally, yes, though they might have lost some power over the years. 17-Dec-19 09:14 PM I have a soviet 26mW HeNe if that counts 17-Dec-19 09:14 PM still lases perfectly, quite bright too 17-Dec-19 09:14 PM ~10% output per decade as long as users have been kind to it 17-Dec-19 09:14 PM does that apply to all henes? 17-Dec-19 09:14 PM I know pretty much the exact date mine was made 17-Dec-19 09:14 PM which is to say, nearly 30 years ago! 17-Dec-19 09:14 PM oh look, a shiny. 17-Dec-19 09:14 PM https://www.ebay.com/itm/YOKOGAWA-Optical-Power-Meter-TB200-W-405-660-785nm-Red-Blue-Laser-Sensor-Module/181347193434 17-Dec-19 09:14 PM but calibrated for the wrong inputs :< 17-Dec-19 09:14 PM found one that goes up to +5dBm, but it doesn't look like it's built for fibers 17-Dec-19 09:14 PM super cheap 17-Dec-19 09:19 PM The Soviet HeNe should work just .3fine. 17-Dec-19 09:19 PM That's good 17-Dec-19 09:19 PM Are fiber power meters useful for this at all? 17-Dec-19 09:19 PM The kind that have direct access to the photoelement anyway 17-Dec-19 09:29 PM It should work. 17-Dec-19 09:30 PM they're too cheap to not buy and try 17-Dec-19 09:49 PM ok @Mason_Yu, so that seller replied, tracking is available 17-Dec-19 09:49 PM I also found a full DS for this guy 17-Dec-19 09:49 PM https://www.ebay.com/itm/CEO-YAG-RB-64688-Diode-Pumped-Nd-YAG-Rod-Laser-Module-64688-7000-hours-used/262093141354 17-Dec-19 09:49 PM which is a 5% discount if we buy 2 17-Dec-19 09:49 PM http://www.tsukasa-tec.co.jp/product/laser/documents/Typical_RB_Series_Performance_info.pdf 17-Dec-19 09:49 PM Northrop Grumman! 17-Dec-19 09:49 PM the rod looks quite clean 17-Dec-19 09:49 PM and there's a video of it running on youtube! 17-Dec-19 09:49 PM by none other than rocketman 17-Dec-19 09:49 PM https://www.youtube.com/watch?v=4hrUUBR9rts 17-Dec-19 09:49 PM seems like he even has the same ebay laser, since the wires are also cut 17-Dec-19 09:53 PM That seems like a better deal to me. Cheaper and we know it works 17-Dec-19 09:53 PM AND there's a whole writeup 17-Dec-19 09:53 PM https://qumoptly.github.io/laser/site/Laser%20YAG%20DPSS%20Northrop%20Grumman%203x50.html 17-Dec-19 09:53 PM with teardown pics! 17-Dec-19 09:54 PM Hey, I really need to study now, it's 1:00 in the morning. But I think we're close now 17-Dec-19 09:54 PM Studies come first, I'll just mention you when I have info 17-Dec-19 09:54 PM don't have to reply right away 17-Dec-19 09:55 PM Wow, that's a nice teardown 17-Dec-19 09:55 PM Interesting arrangement of bars, alignment here is not nearly as critical I guess 17-Dec-19 09:56 PM Rofin too! 17-Dec-19 09:56 PM they're all like that! 17-Dec-19 09:56 PM Man I want an optical table (and somewhere to put it) 17-Dec-19 09:57 PM replace all your tables with optical tables 17-Dec-19 10:39 PM why are they so expensive 17-Dec-19 10:39 PM is it because they're heavy 17-Dec-19 10:40 PM they're super flat 17-Dec-19 10:40 PM also super heavy and super drilled 17-Dec-19 10:40 PM A friend was offered a practically new massive optical table with vibration isolation 17-Dec-19 10:40 PM Only caveat was a wall was going to need to be taken down and a craned called. 17-Dec-19 10:40 PM Surplus gizmos in Portland had a few small tables for 150$ 17-Dec-19 10:42 PM so they're like pianos but worse 17-Dec-19 10:42 PM yes 17-Dec-19 10:42 PM if you bend a piano you generally don't get fired 17-Dec-19 10:42 PM there is sort of one hack to make an optical table if you have a surface plate 17-Dec-19 10:42 PM superglue lol 17-Dec-19 10:42 PM 123 blocks and superglue 17-Dec-19 10:43 PM ooh 17-Dec-19 10:44 PM i dunno if all tables do this, but the ones that float probably add a good bit of cost too 17-Dec-19 10:45 PM yep, there's some tables that float 17-Dec-19 10:45 PM they usually float on smaller, stubbier tables. 17-Dec-19 10:45 PM or huge granite blocks 17-Dec-19 10:45 PM and if you buy a used table that floats, you should make sure that part works 17-Dec-19 10:45 PM i have like, a slab of aluminum with a bunch of 1/4"-20(?) holes drilled in it that came out of a bell jar thermal evap thing and i'm not sure if there's any interchangeability in the standards around it 17-Dec-19 10:45 PM (or, at least, it seems like it was meant to be modular in that way) 17-Dec-19 10:45 PM i saw some weird pneumatic optics table feet on fleabay and i loved them tbh 17-Dec-19 10:45 PM vibration isolation is fascinating 17-Dec-19 10:57 PM okay so 17-Dec-19 10:57 PM my HeNe laser is probably dead 17-Dec-19 10:57 PM but i do have a 50mW DPSS green laser thing 17-Dec-19 10:57 PM i wonder how light output scales with current 17-Dec-19 10:57 PM .. i should throw together a curve tracer sometime 17-Dec-19 11:05 PM nonlinearly 17-Dec-19 11:11 PM so u need new HeNe? 17-Dec-19 11:11 PM you have a vacuum chamber at -7 @qualia 17-Dec-19 11:11 PM it's only natural that you must refill your hene 17-Dec-19 11:11 PM with hene 17-Dec-19 11:12 PM the capillary tube on the inside seems misaligned or cracked in some way 17-Dec-19 11:12 PM just the typical hene thing with em 17-Dec-19 11:12 PM I like the HeNe colors 17-Dec-19 11:14 PM https://twitter.com/profanegeometry/status/1207164808300097536?s=19 my understanding is that the outside of the thing shouldn't be glowing in the way it is 17-Dec-19 11:14 PM second image 17-Dec-19 11:14 PM you can't have enough HeNe tubes in your lab 17-Dec-19 11:14 PM no that's normal 17-Dec-19 11:14 PM oh? huh 17-Dec-19 11:14 PM I believe it's just gassy 17-Dec-19 11:14 PM it's not lasing 17-Dec-19 11:14 PM mm 17-Dec-19 11:14 PM yeah 17-Dec-19 11:15 PM ok i have a small induction heater 17-Dec-19 11:15 PM i wanna hit the getter ring with it 17-Dec-19 11:15 PM ok 17-Dec-19 11:15 PM that could work 17-Dec-19 11:15 PM there's one other thing you can do 17-Dec-19 11:15 PM get a tank of helium and bathe the laser in it for a week 17-Dec-19 11:15 PM hm 17-Dec-19 11:16 PM yeah that works 17-Dec-19 11:16 PM I've heard stories that this resurrects them 17-Dec-19 11:16 PM i could do that 17-Dec-19 11:16 PM if helium wants to leak out, you can force it to leak back in 17-Dec-19 11:16 PM sam's laser FAQ says it 17-Dec-19 11:16 PM so it must be true 17-Dec-19 11:16 PM sam's site is wonderful 17-Dec-19 11:17 PM yeah best laser resource ever 17-Dec-19 11:17 PM I mean compendium wisr 17-Dec-19 11:17 PM wise 17-Dec-19 11:17 PM you want to use it for a wavemeter? 17-Dec-19 11:17 PM as the reference? 17-Dec-19 11:19 PM yeah 17-Dec-19 11:19 PM or try to 17-Dec-19 11:20 PM yeah ok 17-Dec-19 11:20 PM i want to try and use it in the process of cobbling together an optical spectrometer 17-Dec-19 11:20 PM and then i'd like to try doing imaging with it 17-Dec-19 11:20 PM at which point i may need.. more laser than this 17-Dec-19 11:22 PM eheheh moat las0rs 17-Dec-19 11:22 PM moar 17-Dec-19 11:22 PM like cleaning windshields with laser 17-Dec-19 11:23 PM that's what the oxygen plasma asher is for 17-Dec-19 11:23 PM ahhh ok! 17-Dec-19 11:34 PM do you also need it for tuning diode lasers? 18-Dec-19 12:02 AM (that's my application) 18-Dec-19 12:08 AM i want to tune everything i own eventually 18-Dec-19 12:08 AM or at least precisely quantify whatever its doing 18-Dec-19 12:08 AM i don't know much about how you would tune diode lasers specifically 18-Dec-19 12:10 AM I'm going to see if cheap chinese telco optical power meters are good for measuring laser power 18-Dec-19 12:10 AM they should be 18-Dec-19 12:10 AM ok like with external cavities or the internal one by temperature and current regulation 18-Dec-19 12:11 AM yep 18-Dec-19 12:11 AM normal LD are pretty wide band amps 18-Dec-19 12:11 AM that's also y they tend to laser in many internal cavity modes ^^ 18-Dec-19 12:11 AM compared with narrow band amplification media like HeNe 18-Dec-19 12:13 AM HeNe is super nice for calibrating stuff 18-Dec-19 12:13 AM you power it up, let it get warm, and you get a rock solid output 18-Dec-19 12:13 AM or more multi narrow bands of course 18-Dec-19 12:13 AM some henes are filtered internally! 18-Dec-19 12:13 AM some are unfiltered on purpose 18-Dec-19 12:14 AM yeah and relatively easy to stabilize 18-Dec-19 12:14 AM but ok via fp cavity length most CW stuff is easy to stabilize ^^ 18-Dec-19 12:14 AM 'easy' 18-Dec-19 12:14 AM but having wavemeters/osa is of course nice for many analytical things 18-Dec-19 12:24 AM ooo 18-Dec-19 12:24 AM i should fumble around fleabay for a nice HeNe setup 18-Dec-19 12:26 AM Yeah this laser channel has me saying that way to often 18-Dec-19 12:26 AM assuming i can't get my tube lasing anyways 18-Dec-19 12:26 AM Should we just call this lasers and optics now? 18-Dec-19 12:26 AM keep HV in the name 18-Dec-19 12:26 AM I feel like I want to get a less powerful HeNe laser 18-Dec-19 12:27 AM I think anything high voltage just happens other places though 18-Dec-19 12:27 AM and a slightly more convenient one at that 18-Dec-19 12:27 AM it's a bit hard to wrangle a meter-long 3kg tube 18-Dec-19 12:27 AM And the lasers are kind of dominating this channel... 18-Dec-19 12:27 AM just merge this and radiation into #electromagnetics 18-Dec-19 12:27 AM (not really but) 18-Dec-19 12:28 AM I mean I could 18-Dec-19 12:28 AM But also no 18-Dec-19 12:28 AM could snap high voltage onto semiconductor 18-Dec-19 12:28 AM mmmm 18-Dec-19 12:28 AM they're intertwined enough to be relevant 18-Dec-19 12:29 AM Not really I dont think 18-Dec-19 12:29 AM could also just make this the laser channel and make a new hv/pulsepower channel 18-Dec-19 12:29 AM yep 18-Dec-19 12:29 AM it's not like the server is huge and cluttered 18-Dec-19 12:29 AM When this channel was high voltage i think there was like 20 messages total after several months 18-Dec-19 12:29 AM So im not really sure if we need a dedicated channel for it tbh 18-Dec-19 12:30 AM high voltage for high voltage's sake is boring 18-Dec-19 12:30 AM #off-topic-thats-sometimes-on-topic-and-is-also-hv 18-Dec-19 12:31 AM Yeah i think thats what it comes down to 18-Dec-19 12:31 AM I'm surprised there's not a lot of HV talk to be honest 18-Dec-19 12:31 AM There is 18-Dec-19 12:31 AM just not here 18-Dec-19 12:32 AM well, I guess #lasers_and_optics it is 18-Dec-19 12:32 AM As qualia said it just happens in relationship to other things 18-Dec-19 12:32 AM fair enough 18-Dec-19 12:32 AM i kinda want a pulsed power channel though 18-Dec-19 12:32 AM that in particular is a way undertapped niche 18-Dec-19 12:33 AM because it's hard and scary 18-Dec-19 12:33 AM puts on management hat I have reorganized the servers main verticals to more accurately represent the needs and uses of the users take off management hat 18-Dec-19 12:33 AM That almost hurt to write 18-Dec-19 12:33 AM So pulsed power eh? 18-Dec-19 12:34 AM great thanks let's touch base in the AM after standup 18-Dec-19 12:34 AM yeh maybe! 18-Dec-19 12:35 AM speaking of wavelength meters 18-Dec-19 12:35 AM https://www.youtube.com/watch?v=wXVKHLXO-po 18-Dec-19 01:00 AM speaking of sam, i forgot his ebay store carries many delights https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F302905123013 18-Dec-19 01:00 AM yeah 18-Dec-19 01:00 AM (with many more reasonable doodads within) 18-Dec-19 01:01 AM siliconsam also has HeNe kits 18-Dec-19 01:01 AM power supply plus tube plus sockets 18-Dec-19 01:01 AM i'm Considering 18-Dec-19 01:01 AM specifically a stabilized kit 18-Dec-19 01:01 AM have had his piezo interferometer in my watchlist a while 18-Dec-19 04:50 AM so who's going ahead with building that dang YAG? 18-Dec-19 05:38 AM would be nice 18-Dec-19 05:38 AM some of my caps 18-Dec-19 05:38 AM and boom 18-Dec-19 05:38 AM literally 18-Dec-19 05:38 AM how would one design a q-switch for that kind of power 18-Dec-19 06:15 AM Sizing :p 18-Dec-19 06:25 AM for a certain laser of 150-200W of 532nm Q-switched greenlight 18-Dec-19 06:25 AM the Q-switch needs 75-150W of RF 18-Dec-19 06:25 AM https://gandh.com/wp-content/pdfs/IWDS003V1_0Super_AO_Q_Switch.pdf 18-Dec-19 06:25 AM similar to that 18-Dec-19 06:29 AM That's too small 18-Dec-19 06:29 AM 16mm vs 7/8" rod diameter, also power density of that will be insane 18-Dec-19 06:30 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-CE101.png 18-Dec-19 06:30 AM daym 18-Dec-19 06:31 AM Mechanical q-swtich could work? (if you time things well) 18-Dec-19 06:31 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-82481.png 18-Dec-19 06:35 AM what power density are we talking? 18-Dec-19 06:37 AM It depends on a lot of factors, but with this length and size of the gain medium, you can bet there's a lot of joules pumped up in it and can be released in as little as 100 ns 18-Dec-19 06:38 AM hehe 18-Dec-19 06:40 AM That's one thing I'd like to calculate based on resonant cavity length, output coupler properties, rod diamter and length, pumping power and gain medium properties. But it's a lot of differential equations it seems. 18-Dec-19 06:43 AM Well I take that back, it has been solved for us: 18-Dec-19 06:43 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-C9560.png 18-Dec-19 06:53 AM Let me put the entire lecture note in #resources , not much activity over there for a while now 18-Dec-19 09:23 AM holy buckets that is a terrifyingly large nd:glass rod 18-Dec-19 09:23 AM (Sam eBay listing posted earlier) 18-Dec-19 09:27 AM He's got an even bigger one, over a meter long 18-Dec-19 09:48 AM that seems like a 'i have a dedicated laser building' level project. 18-Dec-19 09:57 AM someone's gotta build the first hobbyist-scale indirect-drive ICF facility eventually 18-Dec-19 10:15 AM a model one would be cute 18-Dec-19 10:15 AM a load of lil laser diodes in fake tubes 18-Dec-19 10:15 AM focusing in on some flash powder xD 18-Dec-19 10:15 AM puff 18-Dec-19 10:25 AM You generally don't use active q switching in flash pumped lasers, it's very complicated to sync. You just use a passive q switch crystal 18-Dec-19 10:25 AM It absorbs light to a certain point and then creashes 18-Dec-19 10:37 AM Also @MCP-TCW it's likely that I will try building one 18-Dec-19 11:04 AM And I though I had large Nd:glass rod... 18-Dec-19 11:04 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/nd-glass-97153.jpg 18-Dec-19 11:06 AM oooo 18-Dec-19 11:06 AM @Deleted User You mean you want to get this? https://www.ebay.com/itm/Gargantuan-Nd-Glass-Laser-Rod-with-4-Giant-Xenon-Flashlamps-Over-1-Meter-Long/302905123013 18-Dec-19 11:07 AM no no 18-Dec-19 11:07 AM the pumps we're talking about 18-Dec-19 11:07 AM Okay, I thought you were actually crazy for a second there 18-Dec-19 11:08 AM As if we're not crazy for wanting to build our own lasers that pulse in triple-digit kilowatts 18-Dec-19 11:09 AM Well, passively q-switched that massive rod will be well into the gigawatt range. 18-Dec-19 11:09 AM I did a quick calculation and got triple digit gigawatt 18-Dec-19 11:10 AM "Why is there a hole in my laser power meter and hand now" 18-Dec-19 11:10 AM oooo 18-Dec-19 11:10 AM do eeett 18-Dec-19 11:10 AM I might build a tiny ruby laser later, but I want something practically applicable now 18-Dec-19 11:10 AM I may have three 10 kV 100uF cap that will be retiring soon 18-Dec-19 11:10 AM They were used in another government laser project 18-Dec-19 11:10 AM o gawd 18-Dec-19 11:10 AM ooo 18-Dec-19 11:10 AM do they have inductance specs? 18-Dec-19 11:11 AM No, but they are quite low (meant for pulse power) 18-Dec-19 11:12 AM are they the funky recessed single terminal sort? 18-Dec-19 11:12 AM (scyllac iirc) 18-Dec-19 11:12 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Capacitors-231E5.jpg 18-Dec-19 11:12 AM I'm going to need to dig through my resources for pulsed gas lasers. Caps like those would be perfect for it 18-Dec-19 11:12 AM oo neat 18-Dec-19 11:12 AM beautiful doorstops 18-Dec-19 11:12 AM @Mason_Yu you aren't using them for the dpf anymore? 18-Dec-19 11:12 AM these should be enough to pulse like... one of those flashlamps :D 18-Dec-19 11:12 AM I realized one of them may go bad soon 18-Dec-19 11:12 AM And I also realized I need more voltage 18-Dec-19 11:12 AM But I'll pulse with them first before moving on 18-Dec-19 11:14 AM when thegeekgroup in the US collapsed, they sold off a massive stock of huge pulse caps for dirt cheap prices 18-Dec-19 11:14 AM https://www.ebay.com/itm/Aerivox-22KV-Capacitor-By-AeroStar-High-Power-Tesla-Coil-Guaranteed/153579531968 18-Dec-19 11:14 AM Candidate upgrade caps 18-Dec-19 11:14 AM "That is a High Power Tesla Coil" 18-Dec-19 11:15 AM Grammar lol. They're excess from Los Alamos 18-Dec-19 11:15 AM Probably driving some crazy accelerators or maybe lasers 18-Dec-19 11:15 AM With 9 of them you can do serious damage 18-Dec-19 11:16 AM Could be used for driving a pulsed Tesla transformer for fast beam stuff. That's an actually useful Tesla coil lol. Sparks = losses 18-Dec-19 11:16 AM wouldn't want to be the lucky sob to short it with something 18-Dec-19 11:17 AM Huh wasn't this channel about high voltage as well? 18-Dec-19 11:17 AM yes 18-Dec-19 11:17 AM it's still about high voltage in spirit 18-Dec-19 11:21 AM Should still be a place to talk high voltage probably 18-Dec-19 11:25 AM what are your plans safety wise for those eBay DPSS? that pulsed power output seems like something in the realm of no longer trusting goggles 18-Dec-19 11:25 AM but laser stuff is not something i know much about (mostly because i like my eyes) 18-Dec-19 11:26 AM Goggles for indirect-always-wearing 18-Dec-19 11:26 AM camera for staring at the photony bits 18-Dec-19 11:27 AM Yeah, cameras and photodiodes 18-Dec-19 11:27 AM well, at low powers I'll still stare with goggles 18-Dec-19 11:27 AM think "just starting to lase" 18-Dec-19 11:27 AM but as soon as I figure out the power supply, a 50W pump is hellish and it's not going to be near my eyes ever 18-Dec-19 11:27 AM I'll also have a full enclosure over the resonant cavity 18-Dec-19 11:27 AM same here 18-Dec-19 11:27 AM once it's done it's going in a box with an output hole 18-Dec-19 11:28 AM For such high power systems that's something that you would want remote and monitoring with video, like an accelerator lol 18-Dec-19 11:28 AM well, it's still controlled 18-Dec-19 11:28 AM it's not like it's raining mirrors in my room 18-Dec-19 11:28 AM yeah the main thing i was wondering about would be unexpected reflections 18-Dec-19 11:28 AM I'm planning to assemble this whole thing on a piece of extruded aluminium 18-Dec-19 11:28 AM Well there are people selling commercial systems that's much more powerful yet you can walk up right next to it while it's cutting 18-Dec-19 11:28 AM with water running through it for extra chilling 18-Dec-19 11:28 AM and i remember Spirit mentioning wanting to do laser milling or something so i wasnt sure if this was part of that 18-Dec-19 11:29 AM I'm making mine on a piece of Starrett flat stock 18-Dec-19 11:29 AM that's going to be after I get the laser working at all 18-Dec-19 11:29 AM @Mason_Yu if you want to do a group order for the parts we can group order, that'd be preferable 18-Dec-19 11:29 AM and I might need a bit of help getting that RF supply from the US, since the seller doesn't want to ship 18-Dec-19 11:30 AM Hmm, let's figure out the ordering and shipping part once we have a complete list of stuff we're buying 18-Dec-19 11:30 AM The optics part is still a bit tentative and we still need a CC supply for the pump 18-Dec-19 11:31 AM okay, so pump: 18-Dec-19 11:31 AM https://www.ebay.com/itm/CEO-YAG-RB-64688-Diode-Pumped-Nd-YAG-Rod-Laser-Module-64688-7000-hours-used/262093141354 18-Dec-19 11:31 AM suitable qsw: https://www.ebay.com/itm/I-QS027-4S4G-U5-ST1-GOOCH-HOUSEGO-ACOUSTO-OPTICS-I-QS027-4S4G-U5-ST1/254186828064 18-Dec-19 11:31 AM I've also verified that exact q-switch is known to work with the Chinese 50W modules 18-Dec-19 11:31 AM Probably where they're from actually 18-Dec-19 11:32 AM it's a 4mm fused silica switch 18-Dec-19 11:32 AM 3mm laser rod + the manufacturer recommends a small margin 18-Dec-19 11:32 AM Oh I thought you were talking for building GW lasers lol 18-Dec-19 11:32 AM we're building 200-500kW lasers :P 18-Dec-19 11:32 AM not TOO far off 18-Dec-19 11:33 AM o boi 18-Dec-19 11:33 AM I promise 18-Dec-19 11:33 AM if I get rich 18-Dec-19 11:33 AM I will do teardowns on all the stupid-expensive stuff I can find 18-Dec-19 11:35 AM So if we buy two pumps, that's $189.05*2 + $6 + $5 = $389.1 for two pumps including shipping to me($194.55 ea) 18-Dec-19 11:35 AM $159.6*2 + $6 + $5 = $330.2 for two q-switches including shipping to me($165.1 ea) 18-Dec-19 11:36 AM gonna have to work out all your cooling too 18-Dec-19 11:37 AM cooling is the easy part 18-Dec-19 11:37 AM power supplies are harder 18-Dec-19 11:37 AM a 24V 20A supply is ~$40 18-Dec-19 11:37 AM but there needs to be something on top to regulate the power 18-Dec-19 11:37 AM since these need to run at constant current, not voltage, still 18-Dec-19 11:38 AM that's the easy part 18-Dec-19 11:38 AM a 20A constant current supply is not very easy :P 18-Dec-19 11:39 AM New power supplies made for these modules from China is super expensive and heavy to ship, it's like $220 + shipping 18-Dec-19 11:40 AM too much 18-Dec-19 11:40 AM Might be able to ask Reps for a pair, he already designed one for the jenoptik pumps 18-Dec-19 11:40 AM ya 18-Dec-19 11:40 AM that's not too bad tho 18-Dec-19 11:40 AM tbh 18-Dec-19 11:40 AM $220 18-Dec-19 11:40 AM I'd buy it 18-Dec-19 11:40 AM (for myself, not you) 18-Dec-19 11:40 AM :V 18-Dec-19 11:41 AM It weighs too much to ship economically. You can find them on Aliexpress with a markup but much cheaper shipping 18-Dec-19 11:41 AM it's a bit pointless for $200 18-Dec-19 11:41 AM pinged Marco to see if he has any left 18-Dec-19 11:42 AM https://www.ebay.com/itm/Spectra-Physics-Laser-Diode-w-Fiber-Optics-Cable-808nm-Tested-25W/254346100792?hash=item3b38358038:g:SjgAAOSwwKZdKgV8 18-Dec-19 11:42 AM oooo 18-Dec-19 11:43 AM you can get double the power for the same price 18-Dec-19 11:43 AM look for "nlight" 18-Dec-19 11:43 AM https://www.ebay.com/itm/Gooch-Housgo-Dual-Channel-Laser-Q-Switch-w-Mount-4mm-AR-532nm-1064nm-QS027/254358995752?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D57921%26meid%3Db7e8ec763d6d4dfcb38ea96f8bfde496%26pid%3D100005%26rk%3D1%26rkt%3D12%26mehot%3Dpf%26sd%3D254375286371%26itm%3D254358995752%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100005.m1851 18-Dec-19 11:43 AM that looks very custom 18-Dec-19 11:43 AM if you just want raw power, here 18-Dec-19 11:43 AM https://www.ebay.com/itm/nLIGHT-Pearl-P4-110-0886-5-2-A-R02-Mfg-2017-2013-Fiber-coupled-Laser-Tested-120W/254421382143 18-Dec-19 11:43 AM or here 18-Dec-19 11:43 AM https://www.ebay.com/itm/nLIGHT-Pearl-P4-050-0808-3-A-R01-30407-Fiber-coupled-Laser/283280851187 18-Dec-19 11:43 AM but these aren't useful to us 18-Dec-19 11:43 AM because coupling this light to a yag rod is quite hard, as it turns out 18-Dec-19 11:45 AM And side pumping scales much better with power 18-Dec-19 11:45 AM you haven't tried enough ductape. 18-Dec-19 11:45 AM most importantly money 18-Dec-19 11:45 AM :D 18-Dec-19 11:45 AM So here's a list 18-Dec-19 11:45 AM $194.55/pump $165.1/q-switch $60-150/q-switch driver $20/focus lens $25/100% mirror $25/20%T(80% refl) mirror $28*3=$84/optical mounts $25/q-switch mount $20/rail&other hardware 18-Dec-19 11:45 AM 194.55+165.1+20+25+25+84+25+20+100(q driver+shipping) = ~$660 18-Dec-19 11:45 AM things unaccounted for: 18-Dec-19 11:45 AM $40/24V20A power supply $50-90/20A constant current DC regulator(imaginary) $70-100 water cooling 18-Dec-19 11:45 AM 40+90+100 = $230 worst case scenario 18-Dec-19 11:45 AM in total we get $660+230 = ~$890 for the whole laser 18-Dec-19 11:45 AM so... still a lot cheaper than a 50W fiber laser, but not a whole lot cheaper than a 30W one, is it? 18-Dec-19 11:45 AM but we might get shorter pulses... 18-Dec-19 11:56 AM Yeah that's the price for a 30W fiber laser 18-Dec-19 11:56 AM and the INVAR base plate? 18-Dec-19 11:57 AM honestly this one isn't as critical 18-Dec-19 11:57 AM xD 18-Dec-19 11:58 AM my idea is to put it on a water-chilled/reservoir'ed alu extrusion 18-Dec-19 11:58 AM this way it stays stable while being cheap 18-Dec-19 11:58 AM It's possible I can get cheaper optics, but probably not by much 18-Dec-19 11:58 AM I'm just going to stick heat sink onto a big piece of steel I already have lol 18-Dec-19 11:59 AM it will still need forced water 18-Dec-19 11:59 AM in fact for some reason quite high pressure forced water 18-Dec-19 11:59 AM Yeah 18-Dec-19 11:59 AM ~50PSI for the q switch 18-Dec-19 11:59 AM tiny flow rate, but high pressure 18-Dec-19 12:00 PM That will be from an industrial water chiller 18-Dec-19 12:00 PM I will go with a lower tech solution 18-Dec-19 12:00 PM bucket. 18-Dec-19 12:01 PM That works too, I might go with a bucket first considering how much money I'll have after this 18-Dec-19 12:01 PM lol 18-Dec-19 12:01 PM In fact negative money 18-Dec-19 12:01 PM maybe, something better to spend your money on would be good 18-Dec-19 12:01 PM make money? 18-Dec-19 12:02 PM oh, and I forgot a piece 18-Dec-19 12:02 PM glasses - $90 18-Dec-19 12:02 PM aaaaand we're over a grand. 18-Dec-19 12:02 PM or just under 18-Dec-19 12:04 PM Now I can get a 20W fiber laser + galvos and control cards. That's more economical for me ($870 with shipping included) 18-Dec-19 12:05 PM I'm not sure if an extra 30W is worth it 18-Dec-19 12:05 PM if the pulse length is much shorter, it's almost a no-brainer 18-Dec-19 12:05 PM but if we're going to get a few hundred ns at 50W, then it's not really 18-Dec-19 12:05 PM just a quick reminder, does $870 have a quantity discount? 18-Dec-19 12:15 PM No, and for you it'll be like $920 or something like that due to shipping 18-Dec-19 12:15 PM 920 with all the galvos and control cards looks much more reasonable now 18-Dec-19 12:15 PM :( 18-Dec-19 12:15 PM Around $900 anyway 18-Dec-19 12:16 PM such a bummer, I thought it'd be at least worth it building a custom laser 18-Dec-19 12:20 PM There is an advantage of tunability of a custom laser, by playing with the q-switch drive, cavity length, output coupler transmission and so on, it's possible that we can get pulses well below 100ns 18-Dec-19 12:21 PM I was also wrong about the cost of a power supply 18-Dec-19 12:21 PM 400W DC-DC converters are closer to $200 than to $20 18-Dec-19 12:21 PM :< 18-Dec-19 12:22 PM Economics have a habit of trashing interesting ideas... 18-Dec-19 12:22 PM Though I still think it's possible the DPSS option can be superior, especially for some applications 18-Dec-19 12:23 PM If it works the way I think it works, it'd be superior in every way 18-Dec-19 12:23 PM Peak power, pulse length, the ability to easily turn it into a CW laser 18-Dec-19 12:23 PM or QCW 18-Dec-19 12:24 PM For SLM 18-Dec-19 12:24 PM Not to mention the 30 extra watts 18-Dec-19 12:25 PM Yeah, that flexibility is interesting, I'd be interested in just building the cavity without the q-switch first 18-Dec-19 12:26 PM that does drop the price significantly 18-Dec-19 12:26 PM but... still 18-Dec-19 12:26 PM why does money have to be so hard to obtain and keep 18-Dec-19 12:28 PM I'd be willing to swap the q-switch + driver for a galvo and control card and just play with the CW laser first 18-Dec-19 12:29 PM But it's what, $400ish versus $250ish? 18-Dec-19 12:31 PM Yeah, so it's more affordable too. I'll need the galvo anyway for either the fiber laser or the DPSS laser 18-Dec-19 12:31 PM Well, I do need the pulsed functionality 18-Dec-19 12:31 PM I could sell the Chinese pulsed laser for more than the purchase price when I decide to upgrade to DIY, lol 18-Dec-19 12:31 PM considering we're basically buying it 50% off 18-Dec-19 12:33 PM Hmm, I know someone who might be interested in a Chinese fiber laser 18-Dec-19 12:36 PM You could totally resell a few kits to fund a DIY laser 18-Dec-19 12:36 PM or just emitters 18-Dec-19 12:36 PM I can't though :( 18-Dec-19 12:36 PM Why? 18-Dec-19 12:37 PM importing >3 of anything is considered "unregistered commercial activity" in this wreck of a country 18-Dec-19 12:37 PM hell, importing just one kit will be hard to explain to customs 18-Dec-19 12:37 PM I may get in trouble if I import stuff just to sell, my visa does not allow that 18-Dec-19 12:38 PM I don't know much about US visas 18-Dec-19 12:38 PM my laser guy is in a bit of a financial pinch right now so he can't invest in selling/building these here 18-Dec-19 12:38 PM but that might change 18-Dec-19 12:43 PM I will make some low ball offers on some other DPSS modules and forget about the q-switch for now. 18-Dec-19 12:43 PM It looks like for a SLM test a 50W CW laser should be okay 18-Dec-19 12:44 PM I'd buy the Chinese laser kit 18-Dec-19 12:44 PM at least you get something functional to play with, and you can resell the source for a profit 18-Dec-19 12:45 PM I don't know about the reselling part yet. Let me ask around first 18-Dec-19 12:45 PM buy the whole kit for <$900, sell the source used on eBay for $999 18-Dec-19 12:45 PM or just give it to someone who will sell it for you :P 18-Dec-19 01:32 PM @Deleted User What voltage to what voltage 400W DC-DC? 18-Dec-19 01:32 PM 24V @ 20A CV to 20V @ 0-20A CC 18-Dec-19 01:32 PM 100% duty 18-Dec-19 01:33 PM That should be doable with telecom surplus 18-Dec-19 01:33 PM the CV power supply is the easy part 18-Dec-19 01:33 PM but 0-20A constant current is the hard part 18-Dec-19 01:34 PM likely 36-72V "48V" input and 24V output. 18-Dec-19 01:34 PM Hmm true 18-Dec-19 01:34 PM CC would require modding a 48V psu down to 24V 18-Dec-19 01:34 PM done that to get +1kW of 28V for an amplifier 18-Dec-19 01:34 PM are there adjustable telco supplies that go to 0? 18-Dec-19 01:34 PM as far as I know they have ranges of somewhere around 20-58V 18-Dec-19 01:34 PM I have never checked how low the current limit goes on any of mine 18-Dec-19 01:34 PM some do have a minimum load 18-Dec-19 01:35 PM yeah that won't work here 18-Dec-19 01:35 PM And yeah, the current limit might trip it instead of folding back power 18-Dec-19 02:30 PM @Deleted User speaking of import/export inconveniences. Here in the US, export of lasers is a huge issue as they fall under two categories of the US munitions list (USML) which falls under the International Traffic in Arms Regulations (ITAR) 18-Dec-19 02:31 PM These don't 18-Dec-19 02:31 PM They're not ranging lasers 18-Dec-19 02:31 PM it makes the prospect of selling lasers internationally really, really difficult 18-Dec-19 02:31 PM they can also be considered directed energy weapons too though 18-Dec-19 02:31 PM Yeah, these lasers don't fall under that 18-Dec-19 02:31 PM and there's nothing clear-cut in the regulations 18-Dec-19 02:31 PM it's silly broad is all I'm complaining about 18-Dec-19 02:32 PM I've studied ITAR a little 18-Dec-19 02:32 PM It definitely doesn't affect us 18-Dec-19 02:33 PM not saying it does, just making conversation 18-Dec-19 02:33 PM I'm not sure whether I'll end up building a pulsed laser now ;~; 18-Dec-19 02:33 PM Not unless someone buys my thermal camera for a nice price 18-Dec-19 02:33 PM I've wanted to produce and sell a hyperspectral camera but basically said "screw it" after looking deeply into the marketability 18-Dec-19 02:33 PM would have to artificially limit its capabilities just to be in the clear for exporting, silly stuff 18-Dec-19 02:34 PM Hyperspectral in what meaning? 18-Dec-19 02:35 PM as in visible through mid-ir response/imaging 18-Dec-19 02:35 PM heh yeah that'd be hard ITAR 18-Dec-19 02:35 PM 9Hz and <111kpx 18-Dec-19 02:36 PM meanwhile there are dozens and dozens of research papers describing functional principles in excruciating detail 18-Dec-19 02:36 PM there's even been educators threatened with prosecution for teaching foreign students 18-Dec-19 02:43 PM Yeah any fast pulsed stuff will fall under ITAR 18-Dec-19 02:43 PM Pulsed lasers definitely will be regulated in some way 18-Dec-19 02:43 PM If not ITAR then EAR for certain 18-Dec-19 02:45 PM No export licensing required 18-Dec-19 02:45 PM Just no exporting to embargoed countries AFAIK 18-Dec-19 02:45 PM you gotta mess up pretty bad to get on the embargoed countries' list 18-Dec-19 02:45 PM (or be Russia, but IPG has some nice loopholes for that) 18-Dec-19 02:46 PM What type of electronics drive it though? 18-Dec-19 02:46 PM slower than telco drives 18-Dec-19 02:47 PM Wait which lasers are we talking about here lol 18-Dec-19 02:47 PM q-switched and/or seeded nanosecond pulsed fiber lasers 18-Dec-19 02:48 PM Yeah I'd still be careful. Ns pulsed stuff is definitely classified under weapons in the US 18-Dec-19 02:48 PM well then a whole lot of companies should be fined billions 18-Dec-19 02:48 PM :P 18-Dec-19 02:48 PM Since it's used very heavily in weapons lol 18-Dec-19 02:48 PM They may have export licenses though 18-Dec-19 02:49 PM 90% of the laser markers in the world are nanosecond 18-Dec-19 02:49 PM everyone and their dog imports and exports them 18-Dec-19 02:49 PM This might be something @funranium has more info about 18-Dec-19 02:49 PM I just know that coming from pulsed power, any ns pulsed stuff can be highly regulated 18-Dec-19 02:50 PM pulsed power is a bit different 18-Dec-19 02:50 PM Maybe it's different on the optics side, but ns pulsed optics still has a lot of weapons applications in the US 18-Dec-19 02:50 PM Just saying I'd be careful lol, the regulations are super convoluted. There is layer upon layer with a million subsections. 18-Dec-19 02:51 PM well, as long as it's hobbyist I don't think anyone will care 18-Dec-19 02:51 PM assuming you don't start buying and exporting actual rangefinders or something 18-Dec-19 02:53 PM It unfortunately still applies to anyone, regardless of pro or hobby. Probably care less about hobby, but still always a possibility. Individual parts much less so than like a full range finder for sure lol 18-Dec-19 02:53 PM lucky for us, pulsed lasers made in the US are unobtainably expensive! ;) 18-Dec-19 02:53 PM Q-switches are UK made 18-Dec-19 02:54 PM Like I was about 30C of temp range for 1 component on my pulsed plasma thruster from it being regulated under EAR lol 18-Dec-19 02:54 PM https://www.ebay.com/itm/U-S-LASERS-CORP-DIODE-PUMPED-SHG-LASER-SET-HEAD-Q-SWITCH-MODULES-YAG-MARKING/202644483161 18-Dec-19 02:54 PM mason don't throw wrenches into this perfect argument 18-Dec-19 02:55 PM Okay, go on, I'm on your side since I'm doing both lasers and pulse power now 18-Dec-19 02:55 PM well that's it 18-Dec-19 02:55 PM as long you don't buy any actual pulsed laser emitters made in the US, or export from the US 18-Dec-19 02:55 PM ¯\_(ツ)_/¯ 18-Dec-19 02:55 PM but that looks like an awesome find 18-Dec-19 02:55 PM lowball the seller and you might score it 18-Dec-19 02:57 PM https://www.ebay.com/itm/ALLTec-Laser-Head-section-DN-50A-Nd-YAG-Rod-Laser-Module-64688-8000-hours-used/264428689223 18-Dec-19 02:57 PM I linked this one before 18-Dec-19 02:57 PM not worth $900, but you might be able to lowball the seller 18-Dec-19 02:57 PM I'd pay maybe $500-550 for it 18-Dec-19 02:59 PM I contacted the seller to see if he's willing to accept $500 if he ships to China 18-Dec-19 02:59 PM ... can I have it if it's 500 18-Dec-19 02:59 PM He's got 5, so if we buy two at $1000 it might be a better argument 18-Dec-19 02:59 PM oh wow I didn't realize 18-Dec-19 02:59 PM yeah that'd be awesome 18-Dec-19 02:59 PM I'll take the burden of designing a power supply for it 18-Dec-19 03:00 PM Yeah, got to be cheaper than ~$250, that's essentially what it will cost to buy a dedicated laser diode power supply from China and ship it along with this thing 18-Dec-19 03:01 PM $50 for the actual CV supply 18-Dec-19 03:01 PM maybe another $50 for a board 18-Dec-19 03:01 PM and $300-500 of my time, but I'm very philanthropic with my time if it's a cool project 18-Dec-19 03:01 PM the datasheet for that head says 50W CW or 3-65kHz pulsed 18-Dec-19 03:01 PM 1064 18-Dec-19 03:03 PM Rated for CW huh? Good news 18-Dec-19 03:03 PM well yeah, it's a q switch 18-Dec-19 03:03 PM dump power into it and it's transparent 18-Dec-19 03:03 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/allprint_dn50a_zoom-F857E.png 18-Dec-19 03:03 PM chunky 18-Dec-19 03:03 PM There's still some loss inside the q-switch 18-Dec-19 03:03 PM ~10% 18-Dec-19 03:03 PM but you get that loss all the time 18-Dec-19 03:03 PM it's just that at 500kW the loss doesn't seem so big 18-Dec-19 03:03 PM but yeah, if that head is $500 I'm taking it 18-Dec-19 03:03 PM shipping would be... yeosch, 17kg, but I'm willing to make that sacrifice 18-Dec-19 03:29 PM export controls are no fun at all 18-Dec-19 03:50 PM :< 18-Dec-19 05:52 PM There's also Wassenaar to be aware of 18-Dec-19 05:52 PM Much easier to get in problems with that 18-Dec-19 05:52 PM hook up 3x HackRF's instead of rtl-sticks to KerberosSDR and youäd be in breach of wassenaar :D 18-Dec-19 05:54 PM Wassenaar is also a lot more lax in some areas 18-Dec-19 05:55 PM yep 18-Dec-19 06:52 PM @Deleted User WE HAVE A DEAL! 18-Dec-19 06:52 PM YES!!!!!! 18-Dec-19 06:53 PM $500 a piece including shipping to ShenZhen 18-Dec-19 06:53 PM yup, and then one goes to me 18-Dec-19 06:53 PM how much will it cost to ship to me? 18-Dec-19 06:55 PM $198 for air, $110 for surface, all with tracking 18-Dec-19 06:55 PM why must thou twist thine knife 18-Dec-19 06:55 PM I'm going to opt for surface lol 18-Dec-19 06:57 PM what are you two planning to do with these besides playing around with getting them up and running? 18-Dec-19 06:57 PM I want to do laser micromachining and metal 3d printing 18-Dec-19 06:57 PM the latter being a stretch 18-Dec-19 06:57 PM Same for me basically 18-Dec-19 06:57 PM so when do we figure out payment 18-Dec-19 06:58 PM Tomorrow or tonight at the soonest I think 18-Dec-19 06:58 PM Let's work this out in PM? 18-Dec-19 06:59 PM yup 18-Dec-19 07:04 PM Looking forward to y'all receiving and putting into practice. I'm interested in results and process, please do keep the channel updated on it all. 18-Dec-19 07:04 PM For the laser sintering you should check out what all you can manage by using a DLP chip or other spatial light modulators to do dynamic beam shaping and whatnot. E.g. multiple beam steering, spatial and temporal beam shaping, polarizing for optical vortices, endless other applications 18-Dec-19 07:04 PM Neatest thing IMO about beam steering with spatial light modulators is the discrete aspect. Dont have to cross point B to go from A to C. 18-Dec-19 07:18 PM DLP won't do 18-Dec-19 07:18 PM the chip will cease to exist at 50W input lol 18-Dec-19 07:29 PM gonna have to keep an eye on your projects to see if its something i might want to copy in the future 18-Dec-19 07:29 PM way more affordable than i would expect this stuff to be 18-Dec-19 07:37 PM @Deleted User damage threshold is actually quite high believe it or not, nanosecond pulses of tens of joules per cm squared 18-Dec-19 07:38 PM interesting 18-Dec-19 07:38 PM That's at 1064 at least 18-Dec-19 07:38 PM Naturally you beam expand and cover the entire surface, which you'd want to do anyhow to utilize all pixels 18-Dec-19 07:38 PM DLP, or more broadly in literature a DMD (digital micromirror device) won't give you polarization control which is particularly useful for stuff like machining or sintering; for that you would need liquid crystal. Phase control is still very useful though! 18-Dec-19 07:38 PM Fairly decent reference on DMD damage: https://doi.org/10.1117/1.OE.56.3.034108 18-Dec-19 08:41 PM Sorry, been busy with end of year crap all day. Sooooooooooo, laser importing then? 18-Dec-19 08:41 PM The good news, while it drives me crazy at work, is that nothing stops you from importing things. The key is to build the enclosure you need to have to be safe, have the eyewear you need for the alignment when you need to do it, and FIRST THING learn how to do all the maintenance to care of those final optics. 18-Dec-19 08:41 PM Ventilation consideration to make sure you aren't locally venting is important because of LGAC. 18-Dec-19 08:47 PM because of the LG AC units? What'd they do to you? 18-Dec-19 08:48 PM Laser Generated Airborne Contaminants 18-Dec-19 08:48 PM well, the first thing will be actually getting it running 18-Dec-19 08:48 PM first in CW mode, because the q switch requires brains and a people-frying RF transmitter 18-Dec-19 08:48 PM Yes...but you want the enclosure and ventilation handy. 18-Dec-19 08:49 PM there won't be any enclosure for the first tests 18-Dec-19 08:49 PM just covering it up with something 18-Dec-19 08:49 PM and a beam dump of course 18-Dec-19 08:49 PM And spectroscopic grade methanol. 18-Dec-19 08:50 PM you're assuming we didn't just blow our entire budgets on the laser heads 18-Dec-19 08:50 PM I have pure ethanol though 18-Dec-19 08:50 PM I am, but one of the saddest things I run across in labs are people drilling optics because they aren't keeping them clean. 18-Dec-19 08:51 PM well, the lasers we bought have enclosed/sealed optics, they have little silicone tubes going between the sensitive parts of the beam path 18-Dec-19 08:51 PM Pure ethanol will work. Hemostats and Kodak lens wipes to keep things clean are a skill you're gonna develop. 18-Dec-19 08:51 PM You'll always need to clean the final objective. 18-Dec-19 08:52 PM yep 18-Dec-19 08:57 PM Looks like you're set then. 18-Dec-19 10:12 PM lasors 18-Dec-19 10:12 PM Yup 18-Dec-19 10:27 PM Before you ask I had glasses on 18-Dec-19 10:27 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-787BF.jpg 18-Dec-19 10:27 PM The camera missed the pulse but you can just barely see near my finger 18-Dec-19 10:27 PM 495nm which I think is my favourite colour now 18-Dec-19 10:27 PM Ekspla NT340 dial-a-wavelength 18-Dec-19 10:27 PM Is analytical reagent MeOH good enough or should it be HPLC grade? 19-Dec-19 12:06 AM @qualia also on second thought it looks like your HeNe does have a fractured capillary 19-Dec-19 12:06 AM but you should still try to get it to lase 19-Dec-19 12:06 AM a lot more plasma inside the capillary than it appears outside, so it could just be glow 19-Dec-19 12:06 AM or helium leaking out into the outer shell 19-Dec-19 12:31 AM or buying a new tube :3 19-Dec-19 08:39 AM @Metanoic that paper on dmd damage is interesting. have you ever come across a similar reference for liquid crystal devices? 19-Dec-19 04:44 PM @zakqwy not off the top of my head but when I get back home I'll find you one 22-Dec-19 02:36 AM @GigaSquirrel https://iopscience.iop.org/article/10.1088/1367-2630/7/1/253 22-Dec-19 02:36 AM Experimental studies on thin foil targets with thicknesses greater than the wavelength of the laser light have demonstrated the production of beams of protons with energies up to 58 MeV, using a large single-shot kilojoule laser with a wavelength of ~1 μm and an intensity of 3 × 1020 W cm−2 [13]. Two aspects are of particular interest: the proton energy attained and the high-conversion efficiency between the laser energy and the proton beam. In the above studies, a conversion efficiency of 12% was obtained [13]. 22-Dec-19 02:39 AM oh damn 22-Dec-19 02:44 AM And your Terawatt laser. 22-Dec-19 02:44 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/terawattsetup-B84AE.png 22-Dec-19 02:46 AM @Black Lemming With Nd:YAG you need ~10 times less effort than with Ruby for the same power. But getting from 1064 to 532nm is not trivial. Pulsed ruby has quite wide spectrum, so not good for holography. Maybe for shallow scenes it will work. I do have some experience in holography, and I very much recommend you to work with CW 532nm laser. You need to check & fix coherence length first. 22-Dec-19 02:50 AM Disk lasers seem really neat 22-Dec-19 02:50 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/250px-ActiveMirror-499A1.png 22-Dec-19 06:30 AM My hene somehow died, I’ll try the garbage-bag filled with helium soaking bath to rejuvenate my tube and I’ll see if that can save it ( it stopped lasing yesterday ) 22-Dec-19 07:42 AM I've heard the best way 22-Dec-19 07:42 AM is a balloon on each end 22-Dec-19 07:42 AM the pressure helps 22-Dec-19 08:09 AM This implies getting the actual tube out of the housing and have probable harsh time later with alignment or something, no ? 22-Dec-19 09:31 AM So instead retrofitting a new laser implies you don't need to re-do alignment? 22-Dec-19 10:13 AM Let’s say I’m not scared with my « external » mirrors and setup realignment, just scared unmounting the tube out of the neat shiny L-extruded aluminium support, scared I would mess up some not fixable stuff 22-Dec-19 04:37 PM https://www.youtube.com/watch?v=VP011kS_V5Q 22-Dec-19 04:37 PM eek 22-Dec-19 04:39 PM "oh no, firebrick is not enough" 22-Dec-19 04:39 PM "let's angle it so it takes longer to destroy" 22-Dec-19 04:40 PM xD 22-Dec-19 04:40 PM it's a very compact unit 22-Dec-19 04:40 PM yeah 22-Dec-19 04:40 PM pumping disk laser 22-Dec-19 04:40 PM ah it's just diode bar stacks 22-Dec-19 04:40 PM they're about $70 each on eBay 22-Dec-19 04:40 PM for 40W 22-Dec-19 04:40 PM could theoretically build a ~300W laser for under $1000 22-Dec-19 04:40 PM but with a disgusting beam quality 22-Dec-19 04:42 PM indeed 22-Dec-19 04:44 PM Get a bigger Nd:YAG rod and use that powerful diode bars to pump it instead, wouldn't add too much to the cost if you can build the case yourself. 22-Dec-19 04:45 PM Could be an upgrade path for our lasers too 22-Dec-19 04:45 PM Speaking of which, there's really nothing stopping someone from just buying a bunch of diode bars and surround a huge Nd:Glass rod with a lot of them (3 radially, as many as needed for the length of the rod) 22-Dec-19 04:45 PM except money 22-Dec-19 04:45 PM and practical heatsinking 22-Dec-19 04:46 PM And making a water-cooling case 22-Dec-19 04:46 PM could easily pump a few kW into a Nd:YAG rod though 22-Dec-19 04:46 PM indeed 22-Dec-19 04:46 PM not sure the rod would survive however 22-Dec-19 04:46 PM trying to deal with the heat would be a PITA 22-Dec-19 04:46 PM You'd have to cool the rod too 22-Dec-19 04:46 PM watercooling + chillers 22-Dec-19 04:46 PM there are practical limits on the rods too 22-Dec-19 04:46 PM maybe TEK or two 22-Dec-19 04:47 PM one or two hundred TECs 22-Dec-19 04:47 PM This is many kWs, 22-Dec-19 04:47 PM pumping it this hard would require actual chillers 22-Dec-19 04:47 PM the boring fridge kind 22-Dec-19 04:47 PM or a very large bucket 22-Dec-19 04:47 PM Or a very good faucet lol 22-Dec-19 04:48 PM yeah lol 22-Dec-19 04:54 PM https://www.ebay.com/itm/TRUMP-TLF-3200-TURBO-CO2-LASER-POWER-SOURCE/293374329533?hash=item444e7902bd:g:aTcAAOSwm5Nd8uMn 22-Dec-19 04:54 PM remember the coffee table we spoke about? 22-Dec-19 04:54 PM HAha 22-Dec-19 04:54 PM HA 22-Dec-19 04:54 PM buy it 22-Dec-19 04:54 PM I dare you 22-Dec-19 04:54 PM (don't) 22-Dec-19 04:56 PM https://www.ebay.com/itm/Trumpf-TLA700-RF-Drive-Excited-CO2-Laser-700-watts-cnc-cutter/293027117109?hash=item4439c6f835:g:4sEAAOSwjMJXCESV 22-Dec-19 04:56 PM I 22-Dec-19 04:56 PM really, really want to 22-Dec-19 04:56 PM you want it 22-Dec-19 04:56 PM an I could 22-Dec-19 04:56 PM but I won't 22-Dec-19 04:56 PM you could, for $5k? 22-Dec-19 04:56 PM https://i.spirit.re/Y2vQo.png 22-Dec-19 04:56 PM screaming intensifies 22-Dec-19 04:57 PM haha 22-Dec-19 04:57 PM 1.4kW CO2 on the first one 22-Dec-19 04:57 PM I could buy these 22-Dec-19 04:57 PM would destroy my savings xD 22-Dec-19 04:57 PM and my dad would flip out. 22-Dec-19 04:58 PM I read the total CW power is 3.2 kW on the label 22-Dec-19 04:58 PM perfect for light plywood work 22-Dec-19 04:59 PM yes 22-Dec-19 04:59 PM ;P 22-Dec-19 04:59 PM aaah 22-Dec-19 04:59 PM well, there's no bids for $1k 22-Dec-19 04:59 PM I was looking at the label on the front 22-Dec-19 04:59 PM lowball him 22-Dec-19 04:59 PM 1-5kW actually 22-Dec-19 04:59 PM I can't afford to really get it 22-Dec-19 04:59 PM shipping etc. 22-Dec-19 04:59 PM Local pick up only 22-Dec-19 04:59 PM would be amazing, but shipping to the UK 22-Dec-19 04:59 PM yeah... 22-Dec-19 04:59 PM problem! 22-Dec-19 05:00 PM single pallet size 22-Dec-19 05:00 PM I just... 22-Dec-19 05:00 PM can't 22-Dec-19 05:00 PM nope 22-Dec-19 05:00 PM x.x 22-Dec-19 05:00 PM https://www.trumpf.com/filestorage/TRUMPF_Master/_processed_/0/8/csm_TRUMPF-Laser-Amplifier_4244a96b5b.jpg 22-Dec-19 05:00 PM Jeebus, trumpf is up to some wacky stuff 22-Dec-19 05:00 PM https://www.trumpf.com/en_GB/products/laser/euv-drive-laser/ 22-Dec-19 05:05 PM I didn't know Trumpf was into EUV 22-Dec-19 05:06 PM seems it's a colab 22-Dec-19 05:06 PM That was just the laser to produce a plasma source... 22-Dec-19 05:06 PM 457k parts. 22-Dec-19 05:06 PM can't even imagine how much that piece of kit cost 22-Dec-19 05:07 PM This is what comes after it 22-Dec-19 05:07 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/fig1-CC4B9.png 22-Dec-19 05:07 PM *batteries not included 22-Dec-19 05:07 PM and a nice adorable looking staubli bot 22-Dec-19 05:07 PM https://www.laserfocusworld.com/blogs/article/14039015/how-does-the-laser-technology-in-euv-lithography-work 22-Dec-19 05:07 PM With more than 100,000 components, such an EUV lithography system is one of the most complex machines ever built. It is pumped by the most powerful laser system ever made in serial production. In total, it weighs 180 tons and consumes more than 1 MW electrical power. It costs $120 million and is sold out for years. 22-Dec-19 05:07 PM there we go, $120 million 22-Dec-19 05:08 PM "and is sold out for years" 22-Dec-19 05:08 PM they have orders for years to come 22-Dec-19 05:08 PM $120M isn't too expensive though 22-Dec-19 05:08 PM that falls in line with all the other fab gear 22-Dec-19 05:09 PM xD 22-Dec-19 05:10 PM It's 120 million euros 22-Dec-19 05:10 PM minor differences 22-Dec-19 05:10 PM The clean room contains the steppers for photolithography, in addition to etching, cleaning, doping and dicing machines. All these devices are extremely precise and thus extremely expensive. Prices for most common pieces of equipment for the processing of 300 mm wafers range from $700,000 to upwards of $4,000,000 each with a few pieces of equipment reaching as high as $130,000,000 each (e.g. steppers). A typical fab will have several hundred equipment items. ouch 22-Dec-19 05:11 PM Only 30 units installed in 2019 22-Dec-19 05:11 PM so it's still on the highest high side 22-Dec-19 05:11 PM voids warrenty 22-Dec-19 05:12 PM reminds me of that joke 22-Dec-19 05:12 PM "will I die if I try getting into this machine?" 22-Dec-19 05:12 PM "yes, but not from the machine, you'll be dead because of bullets long before you reach it" 22-Dec-19 05:13 PM haha 22-Dec-19 05:13 PM you don't need a bomb to threaten a facility like this 22-Dec-19 05:13 PM just the threat to take your mask off and sneeze 22-Dec-19 05:14 PM imagine the cleanup price if someone puts a contaminated wafer through the process 22-Dec-19 05:14 PM "I want 500k wired to my account and a helicopter exit, or I'll set off a can of deoderant hidden in the fab lab" 22-Dec-19 05:14 PM ... yeah 22-Dec-19 05:15 PM "I have a can of air freshener and I am not afraid to use it" 22-Dec-19 05:15 PM replaces a wafer with a disk of volatile plastic. 22-Dec-19 05:19 PM kill a major chip manufacturer's(intel/ndivia/amd) market by inverting a small square in a photomask 10% into the run 22-Dec-19 05:19 PM actually, they're not maskless... 22-Dec-19 05:19 PM I wonder, is maskless EUV possible at all? 22-Dec-19 05:19 PM I wonder..... is EUV possible... at home... 22-Dec-19 05:22 PM What would be the advantage of maskless EUV? The production rate would not be significantly higher than E-beam and we're talking similar feature sizes here 22-Dec-19 05:23 PM yeah I suppose e-beam is the sensible choice here 22-Dec-19 05:23 PM plus every SEM owner has an e-beam machine in disguise 22-Dec-19 05:23 PM just need to add some minor hardware changes 22-Dec-19 05:28 PM Making an EUV lightsource at home should be feasible, not with CO2 laser onto a tin target but with pulsed Nd:YAG onto Xenon 22-Dec-19 05:28 PM But really, what's the point? 22-Dec-19 05:29 PM There isn't much point to owning a SEM either 22-Dec-19 05:30 PM lol 22-Dec-19 05:30 PM Well if your goal is to make nanometer features then a convereted SEM is still a much better idea than EUV 22-Dec-19 05:31 PM Some day I'll build a SEM 22-Dec-19 05:31 PM Or buy one, whichever becomes available first 22-Dec-19 08:50 PM oh hey @DUIofPhysics https://youtu.be/D9PnopSHPRk?t=1024 22-Dec-19 08:50 PM looks like the USSR outdid Trumpf by a few decades in the gas flow laser department 22-Dec-19 08:50 PM HeN2 glow discharge laser, apparently 22-Dec-19 08:50 PM @Mason_Yu this is a super neat post 22-Dec-19 08:50 PM https://habr.com/ru/post/433222/ 22-Dec-19 08:50 PM looks like a N2 laser can be built very easily 22-Dec-19 08:50 PM use google translate, obviously 22-Dec-19 08:50 PM I wonder if it can be made completely CW, not HF pulsed 22-Dec-19 09:21 PM Oh, I knew how easy a TEA N2 laser is to build, but the longitudinal discharge with a resonantor is new to me. 22-Dec-19 09:21 PM https://deralchemist.wordpress.com/ 22-Dec-19 09:21 PM That's what's interesting to me too 22-Dec-19 09:21 PM longitudinal lasers are new 22-Dec-19 09:22 PM It can only be pulsed, never made completely CW for the same reason as a ruby laser 22-Dec-19 09:22 PM It's a 3 level laser in which there is no long stable pumped state, only a metastable state 22-Dec-19 09:22 PM https://www.youtube.com/watch?time_continue=3&v=iI1X1b5zRfo&feature=emb_logo 22-Dec-19 09:22 PM I like the noise! 22-Dec-19 09:24 PM I wonder what kind of mirrors it needs 22-Dec-19 09:24 PM Because I can totally build one 22-Dec-19 09:25 PM Simple circuit 22-Dec-19 09:25 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/laser1-8E240.png 22-Dec-19 09:25 PM Would make a nice tutorial video 22-Dec-19 09:25 PM The post you mentioned says only a silver coated mirror and an output coupler 22-Dec-19 09:25 PM Hey I can get you some mirrors and output couplers for cheap 22-Dec-19 09:28 PM Who would have thought :D 22-Dec-19 09:28 PM And probably one or two for myself too 22-Dec-19 09:28 PM I'd be interested in making my own 22-Dec-19 09:28 PM A 100% reflective one would be simple, but an output coupler would be challenging 22-Dec-19 09:51 PM https://www.youtube.com/watch?v=cFXY9HgzrpY 22-Dec-19 09:51 PM ha 22-Dec-19 09:51 PM someone did use a HeNe as a nitrogen laser 22-Dec-19 09:51 PM also, whoa 22-Dec-19 09:51 PM https://www.youtube.com/watch?v=-IraMj5gvPM 22-Dec-19 09:51 PM DIY KDP? 22-Dec-19 09:52 PM It requires some glassworking ? 22-Dec-19 09:52 PM looks like not 22-Dec-19 09:52 PM just blow the tube and attach a low pressure nitrogen system 22-Dec-19 09:52 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/1319290441_1667_FT66720_len2schem-504E2.png 22-Dec-19 09:52 PM I wonder what would happen if I replaced the spark gap with a thyratron 22-Dec-19 09:52 PM And bumped the cap values an order of magnitude up 22-Dec-19 09:59 PM It's the same topology as the circuit I showed above, replacing with a thyratron would make it triggerable but a self-breaking spark gap's performance should be more than enough here 22-Dec-19 09:59 PM Self-breaking? 22-Dec-19 09:59 PM ah 22-Dec-19 09:59 PM You charge the spark gap to a certain voltage and it break by itself 22-Dec-19 09:59 PM Well yeah, but I'm talking more in terms of pulse rate 22-Dec-19 09:59 PM soviet thyratrons are a dime a dozen, can handle a few kV at a few dozen amps, and can pulse at a few kHz 22-Dec-19 10:00 PM Oh, going with a thyristor is an option too 22-Dec-19 10:00 PM oh yeah 22-Dec-19 10:00 PM very true 22-Dec-19 10:00 PM Speaking of SHG 22-Dec-19 10:00 PM I found these 22-Dec-19 10:00 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/TB2XXbkyFmWBuNjSspdXXbugXXa_3365237887-10A83.png 22-Dec-19 10:01 PM Beam finders? 22-Dec-19 10:01 PM Yeah 22-Dec-19 10:01 PM they're just microscope slides dipped in a phosphor 22-Dec-19 10:01 PM can't remember which 22-Dec-19 10:01 PM Super cheap and potentially useful for us 22-Dec-19 10:01 PM it's like $30 a kilo 22-Dec-19 10:01 PM you can use a paper note in a pinch 22-Dec-19 10:03 PM The thing is, some of them claim it's a SHG ceramic that frequency doubles and are specifically marketed as such 22-Dec-19 10:03 PM I was a bit off on price 22-Dec-19 10:03 PM it's around $0.90 a gram 22-Dec-19 10:03 PM but it's just a phosphor 22-Dec-19 10:03 PM https://www.alibaba.com/trade/search?fsb=y&IndexArea=product_en&CatId=&SearchText=infrared+pigment 22-Dec-19 10:05 PM Yeah that would make a lot of sense. I guess it's just blatant false advertising 22-Dec-19 10:05 PM well, you can turn it into a ceramic 22-Dec-19 10:05 PM which is what they did 22-Dec-19 10:05 PM dip into slurry, sinter, done 22-Dec-19 10:05 PM https://www.alibaba.com/product-detail/infrared-ray-active-pigment-IR-phosphor_60551020792.html?spm=a2700.7724838.0.0.173956f5AS8bMb&s=p 22-Dec-19 10:05 PM could order a bag of this and make us a bunch 22-Dec-19 10:05 PM oh, here we go 22-Dec-19 10:05 PM https://www.alibaba.com/product-detail/Infrared-Excitation-Pigment-980nm-for-Security_60726911836.html?spm=a2700.7724838.0.0.173956f5AS8bMb 22-Dec-19 10:05 PM "FREE SAMPLE PROVIDE" 25-Dec-19 04:01 AM https://hackaday.com/2019/12/25/laser-welding-with-a-tattoo-removal-gun/ 25-Dec-19 04:01 AM Christmas time 25-Dec-19 10:39 AM That should be possible with the DPSS laser as well since we have full control over pump power and the q-switch. 25-Dec-19 11:31 AM true 25-Dec-19 11:31 AM just a level of powwah 25-Dec-19 11:40 AM @Mason_Yu it won't be 25-Dec-19 11:40 AM that flashlamp laser has pulses in the many mJ range 25-Dec-19 11:40 AM and they're very long 25-Dec-19 11:40 AM several ms 25-Dec-19 11:44 AM https://www.spilasers.com/whitepapers/pulsed-ns-fiber-lasers-they-can-weld-too/ 25-Dec-19 11:44 AM I think it's possible for thin materials 25-Dec-19 11:44 AM Not for super thick metals, but more like thin sheet metal or razor blades 25-Dec-19 11:44 AM It's certaintly possible that we'd need to go to very high pulse repetition rates 25-Dec-19 11:44 AM Our q-switch is capable of at least 100 kHz repetition rate 25-Dec-19 11:44 AM That will be very close to QCW operation 25-Dec-19 12:01 PM Well, we can try 25-Dec-19 12:01 PM That's pretty much the motto of our experiment 25-Dec-19 12:01 PM "Well, we can try" 25-Dec-19 12:03 PM Exactly. There's so many parameters that can be altered here, the resonant cavity length and output coupler transmission should play a role as well 25-Dec-19 12:03 PM I'm really curious how the fiber lasers can change their pulse widths all the way from 9 to 500 ns 25-Dec-19 12:05 PM maybe q switch drive power 25-Dec-19 12:05 PM or q switch opening time 25-Dec-19 12:12 PM I guess you could change the gain of the cavity by messing with losses in the q-switch. Well, yet another parameter to change 25-Dec-19 01:14 PM There are multitudes of ways that you can alter the resonator of a fiber laser. Bending, squeezing, twisting, heating - all alter the beam. You can longitudinally stretch the fiber to physically lengthen the resonator. You can use a semiconductor saturable absorber and adjust the gain - basically a passive adjustable q-switch. I'm leaving out dozens. 25-Dec-19 01:15 PM https://www.spilasers.com/wp-content/uploads/2016/10/SM-S00219-Rev-I-G4-Datasheet_0817.pdf 25-Dec-19 01:15 PM By looking at the pulse shape, can you tell how SPI are tuning their laser pulse lengths? 25-Dec-19 01:15 PM For us it's easy enough to just move the reflectors and output couplers, we also have an adjustable 1-4mm mode aperture in the cavity 25-Dec-19 01:17 PM no, that graph is likely just marketing stock photo anyhow 25-Dec-19 01:17 PM looking at their FAQ, I'm going to assume they're just chirping the pulse and then re-integrating user-chosen sub-bands 25-Dec-19 01:17 PM Start with a broadband pulse, say 600-800nm. You'll have a peak somewhere, maybe another small peak elsewhere, a few valleys, etc. Then put it through high dispersion optics - e.g. a bulk grating, a long run dispersion compensating fiber, or a special tapered fiber that generates a supercontinuum and you'll have various arbitrarily shaped sub-pulses if you look at it as a Fourier transform (which the dispersion effectively just did). Then sample from that dispersed pulse over time, de-disperse and you've got your custom pulse shape. The gotcha is your spectral density is a function of your pulse shape and you don't get to eat your cake and have it too. 25-Dec-19 01:17 PM You could also sample spatially with, e.g. a DMD or MEMs grating 25-Dec-19 01:30 PM Hmm, is it possible they are using a seed laser to change pulse width and control waveform? 25-Dec-19 01:30 PM Like MOPA 25-Dec-19 01:30 PM The laser they are advertising as tunable pulse likely falls in their seed category of products 25-Dec-19 01:30 PM Pulse broadness is only relative to dispersion resolution, though. So if they are reliably manufacturing a volatile spectrum of narrow bandwidth you may still have a pretty narrow line 25-Dec-19 01:30 PM You could use multiple lasers each with their specific pulse but it's a pain and requires relatively expensive solutions to reliably adjust phase for coherent addition. 25-Dec-19 01:30 PM Would be much easier to just have a broad pulse, chirp, sample, de-chirp/compress. 25-Dec-19 01:34 PM That seems much more complicated. I think we don't need to achieve anywhere near their range of pulse width adjustment 25-Dec-19 01:34 PM Perhaps we can achieve something like this by modulating the loss inside the q-switch? 25-Dec-19 01:34 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-8DCD0.png 25-Dec-19 01:36 PM just disperse your pulse 25-Dec-19 01:36 PM pass it through/off a grating, place turnable mirrors at desired points for sampling the spectrum or dumping it, reflect back to second grating to undo the first one's effects. 25-Dec-19 01:36 PM well, not entirely undo as you still want your dispersion effects for the pulse lengthing 25-Dec-19 01:36 PM basic mechanism, though 25-Dec-19 01:40 PM Chirped pulse compression/sampling is something I'd like to play with in the future, but it's not going to be the first thing I try 25-Dec-19 01:40 PM If the tunable parameters we have can be changed to achieve the result I need, then I don't want to have extra complexity in the system that adds cost 25-Dec-19 01:40 PM I am are looking for pulse widths on the order of a few hundred nanoseconds at very fast repetition rates for welding/SLM purposes. 25-Dec-19 01:47 PM SLM is CW/QCW 25-Dec-19 01:47 PM just very very fast scan rates 25-Dec-19 01:48 PM Yeah, the goal is to try and achieve QCW operation with fast switching rate at high power. CW is already given with our system 25-Dec-19 01:50 PM maybe we can ride that edge of edge of lasing 25-Dec-19 01:50 PM by dropping the q switch power down to nothing 25-Dec-19 01:52 PM If you just want a tunable pulse length and not shape you can get by with just two rotatable gratings or linear translating prisms 25-Dec-19 01:52 PM Prisms would be easiest fabrication wise. 25-Dec-19 01:55 PM Chirping with prisms should provide greater tolerance to peak power right? 25-Dec-19 01:55 PM Yeah I guess if it's not possible to get the pulse length we want just from tuning stuff in the cavity, this would be the next step. Thanks for the suggestion! 25-Dec-19 01:56 PM So many next steps while we don't even have the lasers yet 25-Dec-19 01:56 PM It should have just arrived! 25-Dec-19 01:56 PM But nobody is there to get it yet 25-Dec-19 01:57 PM Tomorrow we shall know 25-Dec-19 01:57 PM Umm, they're not going to be there tomorrow neither... Family gathering for three days straight lol 25-Dec-19 01:57 PM In three days we shall know 26-Dec-19 10:32 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-9CB32.jpg 26-Dec-19 10:32 AM Now we wait. 26-Dec-19 11:36 AM "You are doing WHAT?" "Bathing a laser." sirens are heard in the distance 27-Dec-19 12:00 PM https://www.aliexpress.com/item/33016631628.html 27-Dec-19 12:00 PM This is interesting 27-Dec-19 12:00 PM I wonder if that can be collimated into a fiber? 27-Dec-19 12:00 PM At $350 that'd be an amazing deal, a 250W fiber laser for just... cutting stuff 27-Dec-19 12:05 PM at that price point it is definitely worth sending the company an email for more info on what exactly the output is 27-Dec-19 12:05 PM Well, it's just a diode bar stack 27-Dec-19 12:06 PM This could not be coupled to a typical fiber (100-400um) 27-Dec-19 12:06 PM It's also 250W of 808, which means it'll blast through one or two mm of metal 27-Dec-19 12:06 PM yeah but is it just one beam or do you have to worry about more than one output? never seen that sort of window on that diode 27-Dec-19 12:06 PM It's many wide beams 27-Dec-19 12:06 PM A stack of lines 27-Dec-19 12:06 PM This will not blast through metal, as you cannot collimate it to a spot 27-Dec-19 12:06 PM yeah thats what i was thinking based on the bars 27-Dec-19 12:06 PM maybe they have another model of similar price that would be easier to work with lol 27-Dec-19 12:07 PM @Metanoic thoughts? 27-Dec-19 12:07 PM @LRM they have bigger models 27-Dec-19 12:07 PM up to a kW I think 27-Dec-19 12:07 PM All you can do with it is pump YAG rods/slabs 27-Dec-19 12:08 PM You sure? 27-Dec-19 12:08 PM Because fiber coupled packages do this exact thing, except with single bars and cylindrical lenses 27-Dec-19 12:11 PM Absolutely, fiber coupling is a very challenging business. With fiber coupling you integrate everything as compact as possible. For high power fiber coupled - you typically do multiple 100um fibers, which are then fused into 1 thicker fiber. And even then beam quality is very bad and cannot cut metal. You do an Yb fiber amplifier, which gives you high-quality, TEM00 beam in 9um core of the fiber. "Double clad active fiber" is the magic keyword for cutting metal 27-Dec-19 12:11 PM You can cut metal with a bad beam 27-Dec-19 12:11 PM Just not efficiently and not thick 27-Dec-19 12:12 PM Yes, if you are fine with a spot size comparable to physical size of the array... 27-Dec-19 12:13 PM Collimated fiber output could work 27-Dec-19 12:13 PM Anyway, Nd:YAG laser pumped by this thing is very easy and reliable thing to do 27-Dec-19 12:13 PM except for the fact that they're stacked the wrong way 27-Dec-19 12:13 PM so unless you have a square rod you'd need optics to guide the light in 27-Dec-19 12:15 PM Yes, both options are used 27-Dec-19 12:15 PM In 99% of cases 808nm diodes are for pumping Nd:YAG 27-Dec-19 12:15 PM yes 27-Dec-19 12:15 PM these diode bars seem to be for "therapy" 27-Dec-19 12:15 PM as in, just pointing the diode bars at skin lol 27-Dec-19 12:17 PM Maybe 27-Dec-19 12:17 PM they're all over aliexpress 27-Dec-19 12:17 PM diode bar stacks... in handles 27-Dec-19 12:18 PM BTW, I am in contact to a guy selling 45*720mm Nd:Glass rods... He offers me larger and larger items... I am getting scared that it might be a KGB trap for illigal military tech 27-Dec-19 12:19 PM Heh 27-Dec-19 12:19 PM I guess someone unearthed another soviet institute warehouse 27-Dec-19 12:19 PM Yeah 27-Dec-19 12:19 PM Just like nixie warehouses keep popping up in ukraine 27-Dec-19 12:21 PM On the January vacations I plan to take DIY polarimeter, oscilloscope to measure fluorescence time, IR spectrum analyzer and go there to measure all these rods... 27-Dec-19 12:21 PM always wondered how that warehouse stuff works...like are these just sitting abandoned by the owners for 30-50yrs and then someone buys it and realizes the contents? 27-Dec-19 12:21 PM Yes 27-Dec-19 12:21 PM "Buys"? Lol 27-Dec-19 12:21 PM No, he got it for free most likely 27-Dec-19 12:21 PM Or sitting abandoned on the territory of a factory that is 99% dead but still protected/alive 27-Dec-19 12:21 PM Someone rents out the unused buildings, discovers that they're packed full of soviet inventory 27-Dec-19 12:22 PM yeah i was assuming it was more the rent/buying unused buildings sorta thing 27-Dec-19 12:22 PM This guy seems to know laser stuff, so he might be retired from facility or something 27-Dec-19 12:23 PM "Hey I know a guy who did laser stuff, he can sell these crates" 27-Dec-19 12:23 PM Maybe 27-Dec-19 12:23 PM BTW anyone dealt with these relatively new Chinese RF CO2 tubes (30/40/50W)? What is the difference to regular cheap glass CO2 tubes? 27-Dec-19 12:31 PM I've been told that the drive doesn't matter but brand does 27-Dec-19 12:31 PM Reci seem to be the tubes to buy, but quite expensive 27-Dec-19 12:31 PM Told by a friend who also manufactures laser cutters 27-Dec-19 01:14 PM https://hgrinc.com/productDetail/Electrical/Used-Omnichrome-Laser/08190710247/ 27-Dec-19 01:14 PM anyone happen to know what this laser is? A friend thinks it might be helium-cadmium? 27-Dec-19 01:16 PM Yes @Conmega 27-Dec-19 01:16 PM HeCd 27-Dec-19 01:16 PM https://i.spirit.re/vNcnM.png 27-Dec-19 01:18 PM sweet 27-Dec-19 01:18 PM thanks! 27-Dec-19 02:40 PM optical glass that has a reflective coating on a side.. is the wave that is reflected phase shifted (180 deg) if the coating (say, aluminum) has a lower index of refraction? phase shift happens when going from a smaller to larger index of refraction 27-Dec-19 02:40 PM it is possible the numbers the internet is telling me are simply wrong, too.. so more so: should I expect a phase change from any/every reflective coating? 27-Dec-19 02:57 PM so the topic is of interferrance (for measurement of thin films, as brought up elsewhere by me).. but the laser going from air into the glass, small to big index, will undergo a phase shift on it's reflection.. so you actually still get the interferance (regardless of a reflective coating) on the initial beam, and an unchanged one from the transmitted beam.... neat 27-Dec-19 02:57 PM idea of taking long optical flat and grinding a small angle in it, and using that as a scale standard (for position measuring) 27-Dec-19 08:55 PM @Deleted User Good news, I have pictures of the lasers. They both come with a full cover and a back panel for water and electrical connections. 27-Dec-19 08:55 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/0b72737609a08be5f2bfdbc5e7a1e7c1-A6233.jpg 27-Dec-19 08:55 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/5ddf2a1d8fe23252643a1c34ec4d7ee6-078A8.jpg 27-Dec-19 08:55 PM Oh, very nice! 27-Dec-19 08:56 PM Interestingly, it says the maximum power is 100W 27-Dec-19 08:56 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/7284d019cf5b68cc1a95a406fe87f2f0-746E3.jpg 27-Dec-19 08:56 PM It's a generic sticker 27-Dec-19 08:56 PM "certified that it won't output more than 100W" 27-Dec-19 08:58 PM I guess that does make sense. I'm not expecting anything more than 50W. 27-Dec-19 08:58 PM One connector in the front 27-Dec-19 08:58 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/a6e1e368e5a0339bcddf9537aee5a3e8-DEBD5.jpg 27-Dec-19 08:59 PM Probably a shutter or something 27-Dec-19 09:01 PM It's not connected to anything besides ground it seems. All the stuff we need goes out the hole in the back where a connector used to be 27-Dec-19 09:01 PM Well, it looks relatively compact 27-Dec-19 09:01 PM I guess we can talk about shipping in PMs 27-Dec-19 09:05 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/a9beabda0864331aa24ad3d1acf69db5-5EF2C.jpg 27-Dec-19 09:05 PM Can almost see the entire path 27-Dec-19 09:06 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/e7c509e87d5d511826f028e84d916575-28426.jpg 27-Dec-19 09:06 PM You can see the outline of the Nd:YAG rod 27-Dec-19 09:07 PM And the lack of dust on the optics 27-Dec-19 09:07 PM They will be covered during shipping 27-Dec-19 09:07 PM Are they both the same inside? 27-Dec-19 09:07 PM Pretty much yeah 27-Dec-19 09:07 PM Very good 27-Dec-19 09:08 PM Both have internal hoses and wire management. All have wires cut at the external connection on the back panel 27-Dec-19 09:08 PM Well, that doesn't really matter 27-Dec-19 09:09 PM Quite a bit heavier than I thought, 17kg a piece 27-Dec-19 09:09 PM That control panel will probably go 27-Dec-19 09:09 PM I did tell you they were 17kg a piece! 27-Dec-19 09:09 PM and the seller marked them as 17kg 27-Dec-19 09:10 PM Yep, I guess I was expecting the barebone unit with the pictures on the listing 27-Dec-19 09:10 PM But it's good that it comes with covers and all, saves quite a bit of work 27-Dec-19 09:11 PM What it does not save is shipping cost 27-Dec-19 09:12 PM When you go above 15 kg it doesn't matter that much anymore, especially for surface shipping 27-Dec-19 09:12 PM An enclosure helps it get to you intact as well, these were quite poorly packed from the seller 27-Dec-19 09:12 PM They will be repacked with thicker cardboard boxes and more packing material 27-Dec-19 09:15 PM Well, at least we have the actual lasers somewhere now 28-Dec-19 07:52 AM The helium bath worked for my laser btw 28-Dec-19 07:52 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-92353.jpg 28-Dec-19 07:52 AM Output is now nearly 10mw 28-Dec-19 07:52 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-4304A.jpg 28-Dec-19 07:52 AM Hologram made with stormtrooper and ... well a zebra. 28-Dec-19 07:52 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-5A0F4.jpg 28-Dec-19 07:56 AM cool :D 28-Dec-19 08:42 AM @Black Lemming Very interesting, I wonder if one can monitor power output and infuse He in as long as power is rising... 28-Dec-19 08:48 AM Probably, I would however not do it because my ballast resistors are not isolated ( air accessible ) I fear He would arc them if them if running while bathing in saturated atmosphere 28-Dec-19 10:02 AM https://youtu.be/26YTQzKegfA 28-Dec-19 10:02 AM Short video visit of my upgraded lab 28-Dec-19 01:55 PM I've heard that music before.. what is it? 28-Dec-19 01:55 PM some generic thing? 28-Dec-19 03:09 PM Man this channel is so bad for my budget lol, you are all forcing me to reignite my interest in laser systems. Just picked up some very heavy duty pressurized triggered spark gaps a friend of mine that salvaged them from a large pulsed laser system and have been holding them for me. These things are pretty hefty, lot I can do with them. Probably one at least for a high power TEA laser, and use the others for beam stuff. I'll have to post pictures of them later. Got a bunch of large thyratron trigger modules that can be used for these as well. I'll see if I can get a metglass core to play with magnetic pulse compression drivers for fast gas lasers finally. Unfortunately an ebeam pumped gas laser would be very difficult with less than 100s of keV beams, but at least a microwave FEL should be much easier and possible at lower beam potential. 28-Dec-19 03:40 PM Maybe we can open a #holography now xD 28-Dec-19 03:40 PM I have a roll of like 30meters of 40cm wide holographic film ( old stock ), it is still reactive and developing seems okay with chemicals found on eBay. Thing is these are intended to be used with a pulsed ruby laser. My CW Hene is just offset and exposure time is too long. As a matter of why I don’t know if this old film is still a valid and decent investment ( in term of chemicals ). Anyone here would like me to send a sample of this holographic film to check on a pulsed ruby laser if this film is still as good as I hope it is ? 28-Dec-19 03:45 PM Or you can send me some of your film and developer to test it on an overpowered HeNe :D 28-Dec-19 03:46 PM why not both once you get that fancy new laser too 28-Dec-19 03:46 PM The fancy new laser is not red 28-Dec-19 03:46 PM 808+1064 28-Dec-19 03:47 PM keep forgetting that its not a ruby one 28-Dec-19 03:47 PM wonder if the 808 is close enough to work for the film anyway 28-Dec-19 03:47 PM a lot of films have way wider sensitive ranges than they spec out 28-Dec-19 03:48 PM Exposure time: oh look your film is burning 28-Dec-19 03:49 PM or even better "what film?" 29-Dec-19 06:42 AM You'll have better luck with 532nm... 30-Dec-19 01:15 PM anything wrong with the idea of grinding a slight angle to optical glass. beaming a laser/light at it, and reading off the interffereance pattern/lines as a scale/DRO ? 30-Dec-19 01:16 PM Yes, because you won't see any absolute readings 30-Dec-19 01:16 PM it can be incremental.. or I am sure you can glue some sort of absolute "0" position somewhere 30-Dec-19 01:16 PM and track to find that 30-Dec-19 01:16 PM on startup 30-Dec-19 01:16 PM many DROs/scales are not absolute 30-Dec-19 01:17 PM Remember that interference is on the order of wavelengths 30-Dec-19 01:17 PM You'd need to be superhuman to keep track of it manually 30-Dec-19 01:17 PM If you don't, it's probably easier to just build a digital counting fabry-perot interferometer 30-Dec-19 01:17 PM Sam(the one from Sam's Laser FAQ) sells kits to build them on eBay, minus the digital counting part. 30-Dec-19 01:19 PM the patterns can be somewhat large though, I recall one example showing something like 1.5mm per dark sections (from a ~500nm light source) 30-Dec-19 01:19 PM couple that with a library that can detect lines (I have used lib ZXing for reading barcodes from a webcam, it has some decent routines for that) 30-Dec-19 01:19 PM I'm still not sure what the actual issue with this idea is? 30-Dec-19 01:20 PM Well, an interferometer can directly measure sub-micron distances perfectly 30-Dec-19 01:20 PM An incremental encoder 30-Dec-19 01:21 PM right 30-Dec-19 01:21 PM is this not a type of interferometer? 30-Dec-19 01:21 PM It might work, but I'm not sure 30-Dec-19 01:21 PM It'd be a lot harder to build for sure 30-Dec-19 01:21 PM https://en.wikipedia.org/wiki/Air-wedge_shearing_interferometer 30-Dec-19 01:22 PM That would be very hard to build 30-Dec-19 01:22 PM Those angles have to be perfect and flat 30-Dec-19 01:22 PM so, you really only need one piece of glass 30-Dec-19 01:22 PM you would get the phase change on initial reflection, and in phase (with source) on the reflection off the backside/inside 30-Dec-19 01:22 PM which would provide the interferrance 30-Dec-19 01:22 PM but yeah.. the angle would be a task for the grinder.. 30-Dec-19 01:22 PM which isn't an actual problem for me (once it runs) 30-Dec-19 01:24 PM a grinder won't get anywhere near the required precision and flatness 30-Dec-19 01:24 PM I mean, it's not a lapping machine 30-Dec-19 01:24 PM but it is designed for flatness 30-Dec-19 01:24 PM that's what it does 30-Dec-19 01:24 PM we're talking about flatness here that exceeds the flatness of the table 30-Dec-19 01:24 PM a lapping machine is pretty much required 30-Dec-19 01:25 PM and slapping a ceramic wheel with diamond paste isnt good enough to be called lapping? 30-Dec-19 01:25 PM nope 30-Dec-19 01:25 PM I want to challenge that 30-Dec-19 01:25 PM feel free 30-Dec-19 01:26 PM heh 30-Dec-19 01:26 PM not trying to be headstrong or think my machine can rule all.. I just think it is atleast mildly obtainable 30-Dec-19 01:26 PM it has to be optically flat 30-Dec-19 01:26 PM no grinder can get optical flatness 30-Dec-19 01:26 PM not even all lapping machines 30-Dec-19 01:26 PM no? hrmm 30-Dec-19 01:26 PM grinding can get close to lapping on a surface finish level but nowhere close on a flatness level 30-Dec-19 01:27 PM what if what I start with is optically flat, and I grind a backside/reflection side - so surface finish doesnt need to be that good ? 30-Dec-19 01:27 PM instead of a front side 30-Dec-19 01:27 PM your grinder is not optically flat 30-Dec-19 01:28 PM hrmm 30-Dec-19 01:28 PM i do not understand what you are trying to do well enough to give input on the specifics lol 30-Dec-19 01:28 PM it's not the angle that is so much of an issue 30-Dec-19 01:28 PM the angle can be had multiple ways 30-Dec-19 01:28 PM it's the parallelism and flatness of the surfaces 30-Dec-19 01:28 PM just by virtue of the way grinding works it will never be perfectly flat 30-Dec-19 01:28 PM it's the consistency of the angle? 30-Dec-19 01:28 PM which is what flatness is 30-Dec-19 01:28 PM that is why machine surfaces are almost always scraped in after 30-Dec-19 01:28 PM we're talking not only about surface flatness but also overall flatness 30-Dec-19 01:28 PM the total bow of the entire surface 30-Dec-19 01:28 PM that radius has to be massive 30-Dec-19 01:29 PM I have a radius of nearly 1m on that grinder's table.. with a micrometer reading at the extreme 30-Dec-19 01:29 PM regarding rotation/angle setting 30-Dec-19 01:29 PM a radius of 1m means your grinder is ready to go in the scrap metal pile 30-Dec-19 01:29 PM you might have the measurement wrong :P 30-Dec-19 01:30 PM I think we are tlaking different radii 30-Dec-19 01:30 PM I meant the pivoting table, not a bow 30-Dec-19 01:30 PM sorry 30-Dec-19 01:30 PM you want total flatness, not adjustability 30-Dec-19 01:30 PM if you move x back and forth, that should be perfectly flat and parallel 30-Dec-19 01:30 PM sure, and you grind in the magnetic chuck 30-Dec-19 01:31 PM you grind in with the reference to the linear ways 30-Dec-19 01:31 PM yeah, I get it 30-Dec-19 01:31 PM does "optically flat" have a measure at all? of surface finish/flatness 30-Dec-19 01:33 PM usually a wavelength division measurement 30-Dec-19 01:33 PM so half a micron? 30-Dec-19 01:33 PM division 30-Dec-19 01:33 PM wavelength/number 30-Dec-19 01:33 PM https://www.kemet.co.uk/blog/lapping/how-to-measure-flatness-technical-article 30-Dec-19 01:33 PM a ~5x1cm disk might be typically flat to within ~50-60nm 30-Dec-19 01:39 PM going down the rabbit hole of looking at liquid mercury mirrors as flatness standards... not doing anything else today 30-Dec-19 01:39 PM but, just to verify/reitterate, the number one concern is being unable/unreliably able to make optical flatness [with a standard surface grinder] 30-Dec-19 01:45 PM do you plan to be doing much optical work? 30-Dec-19 01:45 PM i do not really understand why you need to skip just using a flat to measure the workpiece 30-Dec-19 01:45 PM the idea here is for a different scale/DRO - not based on an etched/laser glass slide 30-Dec-19 01:46 PM ahh so a chicken and egg problem with measuring hardware 30-Dec-19 01:46 PM I suppose 30-Dec-19 01:46 PM I want/need a DRO system.. and I am wasting time looking at 'cutting edge' ideas 30-Dec-19 01:46 PM because that's what you do when you are on break 30-Dec-19 01:47 PM anyway...i do not think you will really get optical flatness right off a surface grinder no matter what kind of scales you have 30-Dec-19 01:47 PM that is more a lapping application than anything 30-Dec-19 01:47 PM grind in the shape to almost exact dimensions and then lap to flatness 30-Dec-19 01:48 PM is hand lapping a possibility, ontop a surface plate, or no? 30-Dec-19 01:48 PM depends on the goal/part/application 30-Dec-19 01:48 PM sometimes yes, sometimes no, sometimes you do not need the surface plate in the mix at all besides for final inspection 30-Dec-19 01:48 PM https://www.youtube.com/watch?v=j9FsmsjXKx8 good overview video 30-Dec-19 01:49 PM well, you are making it sound not too impossible 30-Dec-19 01:49 PM yup, seen it, thus why I would bring up such a possiblity 30-Dec-19 01:49 PM "truly flat" and "good enough" I think are the distingsions here 30-Dec-19 01:49 PM good enough for my end use.. maybe not a measurement lab 30-Dec-19 01:51 PM ive got two of those soviet optical flats from ebay and those are way more precise than i will ever actually need 30-Dec-19 01:51 PM still nice to know 30-Dec-19 03:54 PM also, apparently what I was describing is a https://en.wikipedia.org/wiki/Shearing_interferometer 30-Dec-19 04:55 PM https://en.wikipedia.org/wiki/Explosively_pumped_flux_compression_generator 30-Dec-19 04:55 PM Ah! the perfect source for my YAG laser flash-lamp 31-Dec-19 12:19 AM Surface grinder will come nowhere close to optical flat quality. Lapping a single workpiece will just have you going out of parallel. 3 plate method or just snag a Soviet flat off eBay for cheap. 31-Dec-19 12:39 AM @Noxz you need to consider the characteristics of object you're inspecting to arrive at the ideal instrumentation. E.g. if it's specularly reflecting then shearing wouldn't be suitable as your fringes will just reflect. If it's not also quite flat then your fringes will be indecipherable. Each transition from dark to light is one wavelength; if you're planning on using a CCD that puts you in the 400-1000nm range. Any adjacent-pixel path length difference greater than your wavelength will be impossible to determine by how many it really differs. White light interferometry transcends this but your source is now expensive. 31-Dec-19 12:41 AM I dont want to be parallel, I want an angle 31-Dec-19 12:41 AM I need to do some lookup maths, but an air-gap version had interferrance lines every ~1.5mm from a ~500nm light source 31-Dec-19 12:41 AM I will actually look this up right now, because my movie just ended 31-Dec-19 12:42 AM What exactly are you attempting? 31-Dec-19 12:42 AM Fringe spacing is dictated by the topology of the object under test 31-Dec-19 12:43 AM oh, I just want a DRO .. and I have enough time left on winter break to go into a rabbit hole of impossibilities 31-Dec-19 12:44 AM Eek I need to rest 31-Dec-19 12:44 AM let's see, the equation was something like 2d/lambda 31-Dec-19 12:44 AM or, err 31-Dec-19 12:44 AM there's another quation for that 31-Dec-19 12:44 AM okay, found the example I saw before.. 31-Dec-19 12:48 AM So you're basically wanting to measure distance using interferometry, yea? And you have control over the reflector/surface being measured? 31-Dec-19 12:48 AM As in you can make sure it's flat, or make it a mirror, or whatever you like? 31-Dec-19 12:50 AM 500nm light, of an air wedge of height 0.02mm on the high side, 10.0cm long (why do they state it in cm.. stupid americans) == spacing interferrance of 1.25mm 31-Dec-19 12:50 AM the idea here is that some of the light reflect off the primary surface, some goes into the glass and reflects off the back side 31-Dec-19 12:50 AM and it is demonstrated without too much difficulty in that regard, which is why it doesnt seem terrible 31-Dec-19 12:51 AM FWIW wedge spacing is very difficult to get right and especially stay right. Making the wedge also very difficult. 31-Dec-19 12:51 AM but what about the wedge being the glass itself, ie, the shear interferrometer 31-Dec-19 12:51 AM a difference from the air gap is you get an initial reflection off the glass out of phase 31-Dec-19 12:52 AM I would try diffractive shearing. Would need to do the math on whether you could get away with inkjet transparency sort of level but that would be my recommendation 31-Dec-19 12:52 AM vs the second reflection in air gap being out of phase 31-Dec-19 12:53 AM You'd basically use two separate orders from a transmissive diffraction grating 31-Dec-19 12:53 AM not sure I know it yet, willl have to look that up 31-Dec-19 12:54 AM I think it would fall under lateral shearing 31-Dec-19 12:57 AM heh, the example numbers from that air gap was 0 deg 0 min 41.25 arc seconds 31-Dec-19 12:57 AM agh, I suck at discord 31-Dec-19 12:57 AM that gives 1.25mm interferrance spcaing from 500nm light 31-Dec-19 12:59 AM My go-to is always telecom lasers and making a scanning michelson/path-difference interferometer by wrapping fiber around a piezoelectric tube so that, when excited, it stretches the fiber in length. Gets you very far - very robust and good response/speed. You could modulate the piezo with a sine wave and extract your movement from any observed difference. You can also use the modern software defined radios to do all the math/extraction. 31-Dec-19 01:00 AM ah, neat trick, is that method called something? 31-Dec-19 01:01 AM Piezoelectric scanning interferometer is what I would look for in literature 31-Dec-19 01:01 AM For the piezo portion I would look for something like "piezoelectric tunable optical delay line" 31-Dec-19 01:02 AM I think my Funamentls of Photonics book talks about them 31-Dec-19 11:30 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20191231_133001-EE8BF.jpg 31-Dec-19 11:30 AM Lil' bitty baby 20W co2. Adorable. 31-Dec-19 11:30 AM Can almost confuse it for a HeNe 31-Dec-19 11:39 AM Angry HeNe with a heavy contamination of CO2, if you streeeeeeeeeeetch the definition. 31-Dec-19 02:10 PM I wonder if you could diffuse some He in that thing 31-Dec-19 02:14 PM you can replace the gas in them pretty freely 31-Dec-19 02:14 PM the issue is that the mirrors are quite specific 31-Dec-19 02:58 PM aww 31-Dec-19 03:21 PM I designed an absolutely tiny laser/LED buck->dc->boost driver that should run from 2.7 to 5.1V 31-Dec-19 03:21 PM https://i.spirit.re/yBD4l.png 31-Dec-19 03:21 PM 9.83x8.1mm 31-Dec-19 03:21 PM Anyone interested in pitching in to do a group prototype run? 31-Dec-19 03:21 PM I already have a slightly larger laser driver in prototype manufacturing, so I don't really want to blow another $100 on this one 01-Jan-20 09:48 AM "marking" 01-Jan-20 10:20 AM Wurth's models are weird 04-Jan-20 12:50 AM I found something interesting 04-Jan-20 12:50 AM https://www.ebay.com/itm/ORIGINAL-Laser-NEATCELL-Spider-Veins-Acne-Mole-Warts-Freckles-Tattoo-Remover/153585705577 04-Jan-20 12:50 AM From what I can gather online, these devices use gain switched diodes! Whatever that actually means, I'm not sure yet. 04-Jan-20 12:50 AM @Mason_Yu you may be interested as this is pulsy stuff. 04-Jan-20 12:50 AM Someone on hackaday said they measured 1.2ns pulses 04-Jan-20 01:02 AM Looks like it's basically overdriving the diode, but with an RF signal so it goes above and below the lasing threshold with that little kick 04-Jan-20 01:02 AM Lower average output power(around diode rating), but still sharp large pulses 04-Jan-20 01:02 AM Very tempted to buy one to pull to bits and see how it works 04-Jan-20 04:06 AM laser freckle remover?? 04-Jan-20 04:06 AM what is this sinister device 04-Jan-20 04:06 AM i haven't seen that style of weird little goggles it comes with in years, huh 04-Jan-20 04:18 AM I want more freckles, not fewer … 04-Jan-20 04:19 AM just turn up the power and exposure time 04-Jan-20 04:19 AM … no 04-Jan-20 04:19 AM not like that 04-Jan-20 04:22 AM Claim: will not hurt the skin 04-Jan-20 04:24 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/busted-CCDCE.png 04-Jan-20 04:26 AM Size? handle Laser Freckle Removal Pen Type? Laser Freckle Removal False Eyelash Craft? Machine Made 04-Jan-20 04:29 AM Skin Type: Laser Freckle Removal 04-Jan-20 04:29 AM nice 04-Jan-20 06:17 AM So, I have been messing around with the microscope. The light assembly is pretty crap, the lenses are dirty, the clamping is loose (good thing, because I will be able to take them out and clean them) But it makes me wonder, is there any reason that forbids me to use a led source? 04-Jan-20 06:17 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200104_150939-CE46D.jpg 04-Jan-20 06:17 AM Light source is just a crappy halogen lamp 04-Jan-20 06:17 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200104_151010-E75D2.jpg 04-Jan-20 06:17 AM Optics assembly. 04-Jan-20 06:17 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200104_151003-EEBBE.jpg 04-Jan-20 06:17 AM Also, does anyone know these optics function on the system? 04-Jan-20 07:40 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200104_163936-5605D.jpg 04-Jan-20 08:09 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200104_170841-D5677.jpg 04-Jan-20 08:09 AM That fingerprint... 04-Jan-20 09:32 AM oops 04-Jan-20 10:00 AM That print came with it 04-Jan-20 10:12 AM what a deal! 04-Jan-20 10:26 AM but it's removable? 04-Jan-20 10:51 AM depends on the coating. Some can be perma-ruined by oils over time 04-Jan-20 12:08 PM yeah had some fckd up coatings 04-Jan-20 01:38 PM @Nixie No regs forbid you to use an LED source and being incoherent lets you get away with a lot more power before you have a chance to do damage to the skin or eye. I really should just keep that graphic for brightness/damage for given light sources from Sliney et al on my phone for occasions like these. 04-Jan-20 02:17 PM Thanks! 04-Jan-20 02:17 PM Also the plan is to only use a camera with the microscope, so if anything has to get damaged is not my retina on the frontline. 04-Jan-20 02:17 PM XDDD 04-Jan-20 02:17 PM I am extremely tempted in using this 100W cob led at 1/20th the nominal power: 04-Jan-20 02:17 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200104_184238-6ED42.png 04-Jan-20 02:17 PM So I have a full "wall of light" 04-Jan-20 02:17 PM instead of a point source 04-Jan-20 02:17 PM Maybe I can even get rid of the collimator? 04-Jan-20 02:21 PM Does the vertical illuminator have provisions for kohler illumination? 04-Jan-20 02:21 PM /scottish accent/ wot? 04-Jan-20 02:22 PM https://www.olympus-lifescience.com/fr/microscope-resource/primer/anatomy/reflectkohler/ 04-Jan-20 02:23 PM I don't think so 04-Jan-20 02:23 PM In fact, playing with the led this evening, depending on how I focused the light, (NOT using the collimator, nor diffuser) I could focus on the led dots. 04-Jan-20 02:23 PM https://youtu.be/ZRZ9_ov6Fak 04-Jan-20 02:23 PM I would definitely check out this video 04-Jan-20 02:24 PM remember, this is the cheapest metallographic microscope I could find...don't expect miracles out of it. 04-Jan-20 02:24 PM Oh yeah I get that 04-Jan-20 02:24 PM But this is pretty easy to do 04-Jan-20 02:24 PM And should really help image quality 04-Jan-20 02:24 PM It's a way of making the light as perfectly uniform as possible 04-Jan-20 02:26 PM Ahh 04-Jan-20 02:26 PM (yes, just watching the video) 04-Jan-20 02:26 PM Extremely interesting 04-Jan-20 02:29 PM All of her videos are really good and informative 04-Jan-20 02:30 PM Definitely have to check that, but there is not much margin of adjustment in this microscope 04-Jan-20 02:30 PM Will do the best I can. 04-Jan-20 02:32 PM It's not a perfect analog for your system, but you should be able to get a pretty go idea about what is going on 04-Jan-20 02:32 PM Totally ^^ 04-Jan-20 02:32 PM Shame the iris broke on the first 20 minutes of use... 04-Jan-20 02:33 PM 3d print one? 04-Jan-20 02:33 PM And then try not to melt it? 04-Jan-20 02:33 PM Not for the current source of light. 04-Jan-20 02:33 PM XD 04-Jan-20 02:33 PM Found them on aliexpress for about 13/16€ 04-Jan-20 02:33 PM I just have to be careful with the trickle spending (a bit here, a bit there, just this detail here, a small piece...and then you find out you spent a lot more money than you should) 04-Jan-20 02:46 PM Lol yeah 04-Jan-20 02:46 PM Funny how small things add up 04-Jan-20 02:56 PM Especially now that I'm jobless, again 04-Jan-20 02:56 PM XD 04-Jan-20 03:17 PM @Deleted User I think I found the diode they used in those "picosecond" laser pens 04-Jan-20 03:17 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-CB6B8.png 04-Jan-20 03:17 PM It looks just like a regular red laser diode 04-Jan-20 03:17 PM kink-free pure cotton laser output 04-Jan-20 03:18 PM lol, someone did a bad job translating datasheets 04-Jan-20 03:18 PM I'm almost certain there's no RF involved in this one 04-Jan-20 03:18 PM only one way to find out 04-Jan-20 03:18 PM It's just a diode overdrived with a current pulse 04-Jan-20 03:18 PM http://www.ti.com/lit/ug/tidue52/tidue52.pdf 04-Jan-20 03:19 PM someone on hackaday said they measured it at a few nanoseconds 04-Jan-20 03:19 PM Calling it gain-switching is stretching it 04-Jan-20 03:19 PM Yeah, 1-8 ns pulsed laser diodes are commonly made, for LIDAR and range finders 04-Jan-20 03:19 PM interesting 04-Jan-20 03:19 PM https://www.hamamatsu.com/us/en/product/lasers/semiconductor-lasers/plds/index.html 04-Jan-20 03:20 PM Figure 14. 100-W, 1-ns Light Pulse 04-Jan-20 03:20 PM yep that's about right 04-Jan-20 03:20 PM They are driven by a simple capacitor discharge 04-Jan-20 03:20 PM Well with a few more components in it but it's not super complicated 04-Jan-20 03:20 PM Seems like there's a lot of positive feedback for the genuine "neatcell" laser and they do say it's picosecond 04-Jan-20 03:20 PM But what's really interesting is the real picosecond laser diodes 04-Jan-20 03:20 PM Something funny might be going on 04-Jan-20 03:21 PM I don't think most of it is genuine 04-Jan-20 03:21 PM probably 04-Jan-20 03:22 PM They put picosecond on there as a marketing term, to make it somewhat similar to the real machines in clinics which output serious power 04-Jan-20 03:22 PM Hell, some Chinese website even advertises femptosecond lasers from a diode in a hand-held pen! 04-Jan-20 03:23 PM Any laser is a femtosecond laser if you dump a few kJ into it 04-Jan-20 03:29 PM https://analogmodules.com/wp-content/uploads/2016/03/766.pdf 04-Jan-20 03:29 PM I would be interested in something like this for fast imaging applications, since the peak power is appreciable 04-Jan-20 03:29 PM I might buy the laser pen just for curiosity sake 04-Jan-20 04:00 PM It'd be interesting to see what it actually is 04-Jan-20 04:00 PM Because people report feeling pain and tingling when using them 04-Jan-20 04:00 PM Not something I imagine you'd get from a 100W pulse from a lidar diode 06-Jan-20 12:31 PM How goes le 1064nm lasers guys? 06-Jan-20 12:32 PM Shipping soon 06-Jan-20 01:53 PM @Mason_Yu I forget if you were asking, but you bought that Hadland Imacon 792, right? The one weird film I was looking at that's been used for it in some research papers is ASA 3200 Polaroid 667 06-Jan-20 01:53 PM which may still be available from fleabay, in questionable condition 06-Jan-20 02:42 PM Yeah I can probably buy the last pack that's still on eBay, that seems to be the only film recommended by the camera manual that can still be found today. When the camera arrives tomorrow I will have a much better idea of how difficult it is to do digital conversion and then evaluate options 06-Jan-20 02:53 PM am excited for whatever you end up imaging with it :D 06-Jan-20 02:53 PM similarly, my high speed camera arrived today.. but i'm stuck at work.. alas 06-Jan-20 02:53 PM alsoalso, i've had my HeNe laser tube stuffed inside a mylar birthday balloon full of helium for a couple days now.. hopefully it does something more interesting than 'continue to not lase at all' 07-Jan-20 11:19 AM hmmm 07-Jan-20 11:19 AM Who's up for DIY EUV? 07-Jan-20 11:19 AM pick up that 3200W CO2 laser from Ebay. xD 07-Jan-20 11:19 AM https://www.youtube.com/watch?v=oIiqVrKDtLc 07-Jan-20 01:38 PM i have a paper somewhere on using plasma foci as pulsed EUV light sources, kinda interesting 07-Jan-20 01:38 PM sorta out of my wheelhouse 07-Jan-20 01:38 PM @Deleted User you have doomed me to a most terrible fate of trying to find a functioning FireWire host in 2020 for this high-speed camera, thanks :D 07-Jan-20 01:41 PM You have a PCMCIA FW card in the box! 07-Jan-20 01:42 PM I don't own a laptop with PCMCIA 07-Jan-20 01:42 PM I do have a laptop with ExpressCard.. 07-Jan-20 01:43 PM I'm curious what high speed camera this is? 07-Jan-20 01:44 PM it's a Redlake MotionScope M2! 07-Jan-20 01:44 PM Oh redlake! 07-Jan-20 01:44 PM I have delt with their fire wire bull before 07-Jan-20 01:44 PM It showed up in #swap-meet and I dove on it with a 50% offer and got it 07-Jan-20 01:44 PM so now all the money i saved on it is going on cables and controllers, lol 07-Jan-20 01:45 PM Lol yeah 07-Jan-20 01:45 PM also a lens, which shows up tomorrow 07-Jan-20 01:45 PM Redlake makes some of the TEM cameras 07-Jan-20 01:46 PM If I'm really slick about it I should be able to get it working in time for a reverse engineering meetup tomorrow to show it off 07-Jan-20 01:46 PM That should be fun 07-Jan-20 01:47 PM Have you worked with any of their hardware on Linux? I suspect most TEMs have a dedicated little hyper-proprietary-software-loaded computer attached at the hip that just does everything the way its supposed to 07-Jan-20 01:47 PM worst case scenario I have to scramble to install Windows 7 x32 on my thinkpad to get the official software working 07-Jan-20 01:48 PM Yeah I've only ran it on Windows 07-Jan-20 01:48 PM I've been through hell and back getting the damn thing to run on 7 when it was built for do though 07-Jan-20 02:05 PM You might be thinking of a different Redlake @AdamMcCombs 07-Jan-20 02:05 PM The high speed camera Redlake doesn't exist anymore, they've been eaten by IDT 07-Jan-20 02:05 PM @qualia good luck getting it to work with 7 07-Jan-20 02:05 PM I had to resort to 32b xp 07-Jan-20 02:05 PM And trust me, it will not work on anything else 07-Jan-20 02:06 PM Yeah I dealt with other redlake hardware 07-Jan-20 02:06 PM Much older 07-Jan-20 02:06 PM I have a MotionScope 1000S! 07-Jan-20 02:06 PM Before they were purchased 07-Jan-20 02:07 PM early nineties hardware 07-Jan-20 02:07 PM very dead, I kinda pulled it apart a bit 07-Jan-20 06:52 PM ah so that's what happened to them 07-Jan-20 06:52 PM yeah I'm fully prepared to finally put together a mission-critical windows 98 machine or five now tbh 07-Jan-20 06:53 PM Hey it's better than nt 07-Jan-20 06:53 PM A bunch of the SEMs I work on a pretty much stuck on nt 4 07-Jan-20 07:06 PM what's hindering you from using a newer OS and compatibility mode? 07-Jan-20 07:53 PM Very poorly written drivers 07-Jan-20 08:08 PM More like they were written for dos 07-Jan-20 08:08 PM So you need the 16 bit environment 07-Jan-20 09:44 PM I know it’s way too mundane for here but nobody else to tell so.... realizing the big MORN laser I got that was in need of repair is way to big for me to drag home, so in storage it stays. To scratch the laser itch in a more convenient garage size I broke down and ordered one of the mini K40 knock offs on eBay for like $345 with shipping and all. Starting to watch the you tube videos on them. Most of them appear to come broken and need some kind of setup/repair on arrival. Also most people just use K40 whisperer and Inkscape. Probably what I will do. I have a circulator/chiller for my diffusion pumps. I will probably put it in line with that system. 07-Jan-20 09:44 PM Any experience with those cheapies? I want to use it for nameplates and such. Also want to experiment with mica. I cut some micas before at about 15 watts. I’m guessing this thing could probably do 15 CW if it’s rated for 35 which they appear to be. 08-Jan-20 03:54 AM @Charles I've got a k40 in my garage, got for a similar price, maybe less, shipped from U.S. 08-Jan-20 03:54 AM (and I'm in U.S.) 08-Jan-20 03:54 AM pretty much worked out of the box 08-Jan-20 03:54 AM I bought an air assist, to keep fumes from getting on the final lens, and also an upgraded lens (better efficiency) 08-Jan-20 03:54 AM k40 whisperer is indeed the best software I found, and yeah inkscape works pretty well (I've never used the commercial tools, or hacked/old copies of them anyway) 08-Jan-20 03:54 AM mine also came with a small water pump, and a crappy exhaust fan which was fine to start with 08-Jan-20 03:54 AM I'm still using the water pump, just cut some holes in a 5-gallon bucket lid and popped it inside under a few gallons of water 08-Jan-20 03:54 AM it's never had any heating issues, but I guess I don't use it that much, and the times I have, it's been at night mostly (usually gets chilly at night here, no matter the season) 08-Jan-20 03:54 AM I think I checked the alignment when I got it, but it was good enough that I didn't mess with it 08-Jan-20 03:54 AM you can just use thermal paper (most receipts today) 08-Jan-20 03:54 AM or get a sheet of something like this https://www.amazon.com/gp/product/B009P8CSDU/ 08-Jan-20 03:54 AM Liquid Crystal Sheet, 20-25C Transition (4x4 inch) 08-Jan-20 03:54 AM I happened to have a cheap Windows (like $80) laptop/tablet that I purchased a few of on a whim, so it just sits next to the laser 08-Jan-20 03:54 AM https://www.amazon.com/18mm-Laser-Assisted-Ideal-Machine/dp/B0094WLPYK 08-Jan-20 03:54 AM that's the air assist 08-Jan-20 03:54 AM if you have a 3d printer, I think models exist for that piece 08-Jan-20 03:54 AM this is the 18mm lens https://www.amazon.com/gp/product/B01DP2HMPK/ 08-Jan-20 03:54 AM I think I had to buy an assorted pack of o-rings at the local harbor freight, so the new lens would be centered correctly 08-Jan-20 03:54 AM this laserable rubber stamp sheet was pretty fun, too https://www.amazon.com/gp/product/B017IHVSLM/ 08-Jan-20 03:54 AM for the air assist hose, I used this https://www.amazon.com/gp/product/B01FYSQSFI/ 08-Jan-20 03:54 AM Semi Enclosed Type Plastic Towline Machine Tool Cable Carrier Drag Chain Nested (10mm x 10mm) 08-Jan-20 07:49 AM Thanks. Looking forward to getting this thing going. 09-Jan-20 03:40 AM https://www.osa-opn.org/home/newsroom/2020/january/a_particle_accelerator_on_a_chip/ 09-Jan-20 03:40 AM “Traditional photonics and intuitive solutions didn’t work and wouldn’t provide a sufficient acceleration gradient and efficiency to build an accelerator,” she says. The small features that manipulate the light inside a waveguide to create the particle-accelerating fields also introduce reflections and scattering, Sapra adds. 09-Jan-20 03:40 AM Instead, the team used a design technique called “inverse photonics,” which computationally searches the full space of possible photonic structures for the shape that optimizes the device’s efficiency and acceleration gradient with minimal damage to the material. The resulting instrument consists of a 500-nm-thick device layer stacked on a 3-μm-thick buried oxide layer, with 30 periods etched over a 30-μm length. 09-Jan-20 03:40 AM https://science.sciencemag.org/content/367/6473/79 09-Jan-20 08:41 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-813EF.png 09-Jan-20 08:41 PM This is the logo of this channel 09-Jan-20 08:48 PM Do you want a better picture? 09-Jan-20 08:48 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-22CF8.jpg 09-Jan-20 08:48 PM Oh man. They put the label on crooked. The photons are gonna be confused! 10-Jan-20 01:52 AM spotted @Deleted User :D 10-Jan-20 01:52 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/2020-01-10_01_50_34-My_first_high_speed_vi-9CBAF.png 10-Jan-20 11:01 AM Hehe 10-Jan-20 12:08 PM haha same on a video I’ve been working off of last couple days 10-Jan-20 12:08 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-90AFC.png 10-Jan-20 12:15 PM ha 10-Jan-20 08:01 PM https://www.go-dove.com/asset/16/14435 10-Jan-20 08:01 PM Who want another 50W pulsed Nd:YAG laser? 10-Jan-20 08:01 PM There's 6 of them on auction by the way 10-Jan-20 08:08 PM "Reserve Not Met" 10-Jan-20 08:08 PM a.k.a "It's $2000 but we don't want to scare buyers away with the unrealistic price" 10-Jan-20 08:38 PM We'll see, they might put it up for auction with a lower reserve in the future if it's not met 10-Jan-20 08:38 PM There's tons of test equipment coming out of a few sites from Nevada recently 10-Jan-20 08:38 PM This one is flashlamp pumped and the laser oscillator can be removed from the top easily 10-Jan-20 08:38 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-D1546.png 10-Jan-20 09:07 PM too bad it is 220 3 phase 10-Jan-20 10:07 PM Way too heavy to ship as a whole, but if anyone is near Nevada and can go in, just taking the laser module and the caps might be worth it on their own 10-Jan-20 10:07 PM For low rep rate operation 11-Jan-20 02:24 PM It's here! 11-Jan-20 02:24 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/JPEG_20200111_172440-7B277.jpg 11-Jan-20 02:24 PM Pretty big image convertor tube 11-Jan-20 02:24 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/JPEG_20200111_172537-599F4.jpg 11-Jan-20 02:24 PM It comes with a removable focus view port with optical mounts inside 11-Jan-20 02:24 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/JPEG_20200111_172808-0FC75.jpg 11-Jan-20 02:24 PM Should be able to make use of this to adapt it for digital cameras 11-Jan-20 02:29 PM power it up! 11-Jan-20 02:53 PM Well it powers on, now I need to figure out how to get an image in focus mode 11-Jan-20 03:12 PM Arrrgh, the mechanical shutter is operated by a cable release and I don't have a thing that can open it 11-Jan-20 03:12 PM I don't know what that lever thing in the front of the lens mount is, but it's disconnected from the shutter completely 11-Jan-20 03:12 PM The lens mount is on a separate movable focus stage while the shutter in directly in front of the photocathode 11-Jan-20 03:29 PM is it a standard remote shutter control? those are pretty cheap 11-Jan-20 03:34 PM It might be, it's really deep inside the camera though 11-Jan-20 03:34 PM I don't even have a regular standard cable release shutter control on hand, have to get one I guess 11-Jan-20 03:36 PM deep inside the camera sounds nonstandard 11-Jan-20 03:37 PM it's a nanosecond framing camera 11-Jan-20 03:37 PM very nonstandard :P 11-Jan-20 03:38 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20200111_183714-BE172.jpg 11-Jan-20 03:38 PM I put the shutter speed setting to B for Bulb, and tried to reach down into the bottom of the hole but still couldn't get the shutter to open. I don't want to force it 11-Jan-20 03:38 PM This shutter has been closed for who knows how many decades 11-Jan-20 04:16 PM Okay, bad news 11-Jan-20 04:16 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/JPEG_20200111_191606-6A306.jpg 11-Jan-20 04:16 PM I smelled burnt circuits after a few minutes of powering up the camera in focus mode 11-Jan-20 04:20 PM I'm assuming it's not meant to run in focus mode for a while? 11-Jan-20 04:20 PM Which bit smoked? 11-Jan-20 04:22 PM I can't see anything obvious right away 11-Jan-20 04:23 PM Smell test? 11-Jan-20 04:24 PM I'm doing it, but the smell has dissipated a bit 11-Jan-20 04:24 PM A thermal imager would help a bit 11-Jan-20 04:24 PM My roommate is eating Mexican food right behind me... Perhaps I'm just paranoid? 11-Jan-20 04:24 PM I don't have one 11-Jan-20 04:25 PM Does your roommate's food smell like burning electronics? 11-Jan-20 04:25 PM Can't tell very well with a stuffy nose 11-Jan-20 04:25 PM But I'm going to look through this carefully and inspect for damage 11-Jan-20 04:25 PM Oh, a burnt out fuse 11-Jan-20 04:25 PM Well fingers cross that the fuse actually did its job 11-Jan-20 04:25 PM The whole HV power supply is potted, I really hope it's not dead 11-Jan-20 04:41 PM nanosecond blinky power supplies are not very simple 11-Jan-20 04:41 PM so I hope not 12-Jan-20 01:23 AM I would suspect basic power supply stuff first honestly... if something burnt out in the potting you wouldn't smell the burning unless it got to the point of blowing out the potting 12-Jan-20 01:23 AM so its probably something visible and not potted that burnt 12-Jan-20 01:25 AM Yep 12-Jan-20 01:25 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/JPEG_20200112_042521-44B34.jpg 12-Jan-20 01:25 AM That's a very dead capacitor 12-Jan-20 01:27 AM OH LOL 12-Jan-20 01:27 AM A RIFA 12-Jan-20 01:27 AM hahahah 12-Jan-20 01:27 AM yea those are ALWAYS dead 12-Jan-20 01:27 AM replace with a polymer cap, the redish dipped ones 12-Jan-20 01:27 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/JPEG_20200112_042725-323BB.jpg 12-Jan-20 01:27 AM Yeah I've got some on hand 12-Jan-20 01:28 AM yea those are used in old equipment and retro computers as mains filtering caps... 12-Jan-20 01:28 AM generally you just cut them out and replace them when you can generally it doesn't stop it from working 12-Jan-20 01:28 AM but obviously that is not how its used in this circuit 12-Jan-20 01:28 AM hopefully an easy fix :) 12-Jan-20 01:29 AM But I m just going to inspect the rest of everything just to be sure it hasn't damaged other more delicate circuits 12-Jan-20 01:30 AM yea 12-Jan-20 01:32 AM Hmm I don't have a slow blow fuse to replace the original though 12-Jan-20 01:32 AM Might just stick a fast acting one in there for the moment 12-Jan-20 01:52 AM yea that would be fine 12-Jan-20 01:52 AM it may just blow again though lol 12-Jan-20 01:52 AM so probably order some now :) 12-Jan-20 01:57 AM I already did. This is the plug in module that adjust the framing speed and framing time 12-Jan-20 01:57 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/JPEG_20200112_045658-70F23.jpg 12-Jan-20 01:57 AM Looks quite simple actually, it's part of an oscillator circuit and I think I can ask for the schematics for the faster modules 12-Jan-20 01:57 AM And then make my own module to plug in, so I can get any speed I want up to a few 10s of millions frames per second 12-Jan-20 03:47 AM lol RIFA every time 12-Jan-20 04:00 AM This unit is not that old, it was actually produced in 1992 and has been sitting in its box(with a water-tight seal) for at least 20 years 12-Jan-20 04:00 AM But the RIFA cap still failed. Like all others, it's probably due to moisture ingress 12-Jan-20 04:00 AM After the plastic case cracked 12-Jan-20 05:24 AM yea 12-Jan-20 05:24 AM the plastic they used was bad 12-Jan-20 05:24 AM did not stand up to time 12-Jan-20 12:26 PM Pinned a message. 12-Jan-20 12:26 PM oh no, blue smoke D: 12-Jan-20 07:26 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20200112_091943-F58EF.jpg 12-Jan-20 07:26 PM It blew up in three points and released magic smoke deposits onto the PCB and the case 12-Jan-20 07:26 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20200112_084016-F7BA9.jpg 12-Jan-20 07:26 PM The tube was specially made for this camera. Luckily from what I can tell, no high voltage was actually applied to the tube or any of the oscillator electronics since the low voltage power supply overloaded itself and all voltage rails falled below specification 14-Jan-20 02:16 AM <__ice9#6039> Perhaps consider unit-testing the PSU etc with everything else disconnected, and then just the next stage after that if possible, etc. 14-Jan-20 02:24 AM Yeah that's exactly what I did, I could only measure the low voltage rail outputs though, since the high voltage is only enabled when the camera is operating, which is only during a very short burst 14-Jan-20 02:29 AM <__ice9#6039> Hmm might be testable if you have a capacitive HV oscilloscope probe (I know these are uncommon and costly; I had to build mine). Or perhaps just use a resistor divider and a really fast op-amp or perhaps a JFET to rescale the voltage to something a normal scope can handle (?). Or perhaps try to test the output cap before whichever switching device is used to form the pulse (though you mentioned much of it was potted so idk if feasible). But yes that's a bit annoying. 14-Jan-20 02:29 AM <__ice9#6039> At high enough current levels, an inductive oscilloscope probe like the kind used for testing automotive ignition coils might also work. Those are actually very cheap. They won't tell you the actual voltage, though-- just the approximate shape of the waveform. Often good enough to check that something is 'working'-ish 14-Jan-20 02:29 AM <__ice9#6039> Not sure of frequency response for those, though. The fastest thing I have used it on was only 50kHz.... 14-Jan-20 02:29 AM <__ice9#6039> That kind needs a dummy load though. 14-Jan-20 02:36 AM Yeah the current levels in this camera is not enough for that 14-Jan-20 02:36 AM <__ice9#6039> Whereas the capacitive kind can just be directly in contact with the HV contact under inspection 14-Jan-20 02:36 AM <__ice9#6039> Figures. 14-Jan-20 02:39 AM Unfortunately I only have high voltage scope probes up to ~3kV, the camera operates at 18kV 14-Jan-20 02:39 AM I have inspected everything else except the potted supply, and I don't see anything wrong right away, so I'm just going to power it up again after the correct fuse arrives 14-Jan-20 02:48 AM <__ice9#6039> Yeah that's probably reasonable enough. If this is really pulsing for less than a microsecond, a simple resistive divider against the scope probe impedance will likely be too inductive so building a capacitive divider in parallel would probably be necessary. Stray capacitance starts to become a problem at higher frequencies as well, but if you only scaled it down to like 3kV and the source isn't dissipating large amounts of EMI then you could probably get away with not shielding the divider (which in turn eliminates the issue of stray capacitance against the near side of the divider, the most annoying part of building one of these and the reason it is like 45cm long and 13cm wide or something) 14-Jan-20 02:48 AM <__ice9#6039> Given all that, personally I would just try turning it on yeah lol 14-Jan-20 02:51 AM I do have some non-inductive ceramic resistors 14-Jan-20 02:51 AM But yeah, maybe after I get the schematics for everything I will have a better idea of if it's feasible to test. 14-Jan-20 02:54 AM <__ice9#6039> Was there a service manual for it somewhere? It took me a long time to find the one for an x-ray head once but it was totally worth it 14-Jan-20 02:55 AM I have the operator's manual but no schematics 14-Jan-20 02:55 AM And the troubleshooting guide for power supply problem essentially just says send the whole thing back 14-Jan-20 02:56 AM <__ice9#6039> >___< 14-Jan-20 02:56 AM <__ice9#6039> Yeah usually the operators manual is more usage oriented but drops a lot of hints at least, while the service manual if it exists is the one that has the more useful info 14-Jan-20 03:06 AM I did find this 14-Jan-20 03:06 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-58059.png 14-Jan-20 03:06 AM It's the schematic for the plug-in module that enables streak imaging 14-Jan-20 03:06 AM So if the framing module works this is probably the next step 18-Jan-20 12:24 PM https://i.spirit.re/isPeJ.png 18-Jan-20 12:24 PM My tiny laser driver has been manufactured! Now it sails through Europe on a rusty boat. 20-Jan-20 09:02 AM https://www.ebay.com/itm/JDSU-Uniphase-Tunable-Laser-Assy-Model-5205-Tm3-21161398-009/283698400829 Good price on this ITLA. Very useful piece of kit to have on hand. 21-Jan-20 01:51 AM https://phys.org/news/2020-01-laser-diode-emits-deep-uv.html Ultimate cancer ray 21-Jan-20 07:37 AM What would be cool is if they physically printed the paper with said laser.... 21-Jan-20 03:26 PM so how's the YAG projects coming along boyz? 21-Jan-20 03:26 PM Boyz, Girls, Attack Helicopters & Others* 21-Jan-20 03:31 PM Well my laser should be somewhere on a ship in the middle of the Pacific! Currently also waiting on a AD9850 DDS chip to arrive so I can begin work on the HF q-switch driver before the laser gets here 21-Jan-20 04:27 PM My laser should be somewhere on a ship in the middle of continent! 21-Jan-20 04:27 PM I will also be experimenting with q-switch driving if Mason doesn't get acceptable results 21-Jan-20 04:27 PM (we bought the same laser head) 23-Jan-20 07:38 PM lasor 23-Jan-20 07:49 PM <__ice9#6039> UV laser diodes are usually thousands of dollars for well under 1W 23-Jan-20 07:49 PM <__ice9#6039> Currently much more practical to use higher harmonics of YAG DPSS 23-Jan-20 07:58 PM yeah because theyre mad 23-Jan-20 07:58 PM nichia et al 23-Jan-20 07:58 PM I mean like 4500 US$ for a 375nm crappy nichia LD from thorlabs 23-Jan-20 07:58 PM they do that because we let 'em :3 23-Jan-20 07:58 PM I declare war on stupidly overpriced LD for clueless ignorant academia! 23-Jan-20 07:58 PM ok not on the LDs itself 23-Jan-20 07:58 PM but on the prices!1 \o/ 24-Jan-20 02:46 AM so I'm a software person, and have done image processing and machine vision, but not so much with holography... I'm wondering if anyone knows of any good way to explain this RGB image conversion tool, such that I can reimplement it for my own lithography purposes http://www.nanomaker.com/docs/fabrication_of_rainbow_holograms.pdf 24-Jan-20 02:46 AM Like, i know color is often dependent on layer thickness 24-Jan-20 02:46 AM But i can't tell if they're doing greyscale lithography, or if it's somehow dependent on the grating blaze or period 24-Jan-20 02:46 AM Oh, I just answered my own question, I think 24-Jan-20 02:46 AM "The color observed depends on the angle of white light incidence, observation angle and diffraction grating period. Varying the grating period, a reflection can be obtained such that a viewer would simultaneously see three different sites of different colors. These properties make the basis of rainbow holograms. The surface of a sample is filled with diffraction gratings of various periods so that a full-color image could be seen at a proper positioning of a viewer with respect to a light source. A general disadvantage of creation of a colored image with diffraction gratings is that the color of a product changes upon its swinging. Although a grating pack is not a real hologram, these products are commonly called rainbow holograms. Other terms occasionally used are grating-pixel holograms or iridescent holograms OVDs " 24-Jan-20 02:46 AM I'm not sure exact why they change the grating angle 25-Jan-20 10:57 AM Anyone here built a raman spectrometer? 25-Jan-20 10:58 AM I want to. But have not done it 25-Jan-20 10:58 AM I've got all the pieces I think, in addition to my own CCD interface and a concave aberration corrected grating, I've also got a linear array spectrometer and a few lasers 25-Jan-20 10:58 AM I think the only thing I'm missing is the filter and a reflectance probe 25-Jan-20 10:59 AM I wonder how generic fax machine ccd's are 25-Jan-20 10:59 AM My lasers could be too unstable tho 25-Jan-20 10:59 AM as I have one, somewhere and I can't find the datasheet for the exact model 25-Jan-20 10:59 AM I built my interface using the CCD in the Oceans Optics USB2000 25-Jan-20 10:59 AM The TCD1304AP 25-Jan-20 10:59 AM The one I have is some random japanese one 25-Jan-20 11:00 AM They used to be like $11 on eBay 25-Jan-20 11:00 AM That's not bad at all 25-Jan-20 11:00 AM I think 3000 something pixels, though its been more than 5 years since i played with that project 25-Jan-20 11:00 AM https://youtu.be/ut9LfQmaYkU 25-Jan-20 11:00 AM https://youtu.be/nidjp-jl7Fk 25-Jan-20 11:05 AM Aaa those linear CCD's 25-Jan-20 11:05 AM Some in that formfactor on ebay talked about only 256 pixels 25-Jan-20 11:05 AM If I recall 25-Jan-20 11:06 AM Yeah way too little for my tastes 25-Jan-20 11:06 AM But easier to deal with for less rigorous projects 25-Jan-20 11:07 AM Yea 25-Jan-20 11:07 AM Mostly the data rate of the analog is a challenge when people want to use an Arduino 25-Jan-20 11:07 AM And I think the 256 pixel ones might be all digital 25-Jan-20 11:07 AM If they're the TAOS sensors anyway 25-Jan-20 11:15 AM I've got a few of those, but the ridiculously long ones 25-Jan-20 11:15 AM I believe 10680x3 pixels, RGB 25-Jan-20 11:16 AM IIRC BW is better for spectrometers 25-Jan-20 11:16 AM Maybe I should keep my eyes open for more ancient faxmachines to pull apart 25-Jan-20 11:22 AM They're all over ebay, the sensors 25-Jan-20 11:22 AM At least they were 25-Jan-20 11:22 AM yeah, they are 25-Jan-20 11:23 AM I guess I should be less of a cheap bastard :D 25-Jan-20 03:02 PM Oooh those TCD1304AP's are quite cheap 25-Jan-20 03:02 PM And one can find a datasheet for them 25-Jan-20 03:02 PM I'll get one or two. Maybe having the same model as nmz787 will make it more likely for me to do something with it. 25-Jan-20 04:41 PM @rfs I've got code too for them, though it's in pretty crappy C, and also in better shape for the Parallax Propeller https://github.com/nmz787/open-spectrometer/tree/master/firmware 25-Jan-20 04:56 PM @nmz787 I have a modular McPherson spectrometer used pretty much exclusively for raman 25-Jan-20 04:57 PM Neato 25-Jan-20 04:57 PM we normally only use a resolution of 128x64 25-Jan-20 04:57 PM but use a 2400 ln/mm grating 25-Jan-20 04:57 PM for 400nm 25-Jan-20 07:35 PM This is what I've got for basic work, which i was gonna use as a basic baseline for checking my build http://www.science-surplus.com/products/spectrometers 25-Jan-20 07:35 PM Got it with a 600l/mm grating 25-Jan-20 07:35 PM And got a concave aberration corrected grating from china, like 9 years ago, which i can't recall howany l/mm it was... But I remember it should have been high enough to get the raman shift without much aberration in linearity and not widening the signal much either to get (hopefully) usable signal to noise 25-Jan-20 09:55 PM Oh one of the tiny ones, we have a few Photon Control spm-002 spectrometers. I much prefer the McPherson. 25-Jan-20 09:55 PM It's basically just a slit + focusing mirror + grating + focusing mirror + CCD or PMT+slit 25-Jan-20 09:55 PM can resolve individual o2/n2 rotational states 25-Jan-20 09:55 PM the fiber one needs way more light to see anything 26-Jan-20 12:49 AM Oh it appears the McPherson is a monochromator? 26-Jan-20 04:09 AM @nmz787 I am building one at work using Chinese parts and DIY stabilized diode laser. 785nm excitation. ~4000$ total cost. While wavelength stabilization is probably not a must, and spectrometer could have been DIY too, Raman probe with high NA collimator and filter is something which might be harder to DIY. 26-Jan-20 04:58 AM stabilization with an external cavity relatively cheap 26-Jan-20 05:12 AM what sucks is that it need relatively expensive (70 euros) gratings and 200 euro for pzt and 100 for collimation lense :)) 26-Jan-20 05:12 AM do you guys now cheap sources for high pzt? 26-Jan-20 05:12 AM and cheaper than thorlabs sources for gratings and collimation lenses? 26-Jan-20 05:12 AM how hard could it be making gratings your self? 26-Jan-20 05:36 AM no? 26-Jan-20 05:59 AM but I only use it for cooling 26-Jan-20 05:59 AM only wanted to write some "smart" stuff about lasors 26-Jan-20 07:27 AM @N00N depending on how complex the grating is, it can be done DIY 26-Jan-20 07:27 AM I.e. if you want aberration corrected, concave ( so you eliminate some lenses) etc... That's less trivial 26-Jan-20 07:27 AM Also the size of the final grating 26-Jan-20 07:27 AM Like, I can do FIB lithography, but stitching fields of view together is probably going to have some aberrations since my stage isn't using an interferometer 26-Jan-20 07:31 AM how are "holographic gratings" are made? 26-Jan-20 07:31 AM I know they have no blaze - what makes them less effective for laser feedback but hey 26-Jan-20 07:31 AM @nmz787 means that large ones are PITA, right? 26-Jan-20 07:31 AM 'large' like 1/2" * 1/2" 26-Jan-20 07:31 AM I for one only need planar ones 26-Jan-20 07:31 AM with less effective I mean it still works but not as good as it could of course 26-Jan-20 07:31 AM so I guess thorlabs make them via photolitho? 26-Jan-20 07:31 AM on large glass wafers and then chop them down to dices with some wafer saw? 26-Jan-20 07:31 AM so it's like making mirrors - the grinding, lapping, polishing stuff 26-Jan-20 07:31 AM to the convex, concav, planar or whatever shape you want and then photolitho the mask and PVD the metal on it and lift off? 26-Jan-20 07:44 AM Basically, yeah more pita or less efficient 26-Jan-20 07:44 AM thinking about the pain of polishing/lapping mirrors makes me kinda accepting the price now 26-Jan-20 07:44 AM Holographic are made using interference patterns, so possibly more diy friendly to the knowledgeable person 26-Jan-20 07:45 AM hm hm cool then 26-Jan-20 07:45 AM hmm I could use of course already polished surface mirrors as a lazy start 26-Jan-20 08:08 AM Hmm, yeah, or silicon wafers 26-Jan-20 08:08 AM Depending on if you want transmission vs reflection 26-Jan-20 08:10 AM only reflection 26-Jan-20 12:17 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200126_211245-99451.jpg 26-Jan-20 12:17 PM So, my dumpster find laser power meter might not be trash 26-Jan-20 12:17 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200126_211207-257F0.jpg 26-Jan-20 12:17 PM Just needed new batteries 26-Jan-20 12:17 PM I guess the power cable was cut to prevent people form blowing it up 26-Jan-20 12:17 PM as it eats 110VAC 60Hz and this is 230VAC 50Hz land. 26-Jan-20 12:17 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200126_211321-0BE6B.jpg 26-Jan-20 12:17 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200126_211408-DD43E.jpg 26-Jan-20 12:17 PM only twenty years out of cal! 26-Jan-20 12:46 PM I'm sorry, but Kalibroitu just sounds so cute 26-Jan-20 12:46 PM I don't see much that could go out of cal here tbh 26-Jan-20 12:51 PM @N00N Our excitation laser will be stabilized passively using VBG (volume Bragg grating), down to 0.05nm, which is good enough. Completely passive. 26-Jan-20 12:54 PM to be fair, VBG stabilized lasers are very actively temperature stabilized 26-Jan-20 12:58 PM @GigaSquirrel Old school FINMET "Kansallinen mittanormaalilaboratorio" cal sticker at that! 26-Jan-20 01:00 PM gnihihi 26-Jan-20 01:01 PM I think FINMET is now part of MIKES, which means "Mittaus Keskus" whcih in other words is literally "Measurement Center" 26-Jan-20 01:01 PM They do the national standards thing. 26-Jan-20 07:29 PM @nmz787 It can be used as one, I guess. The grating that redirects to the CCD is rotatable so you can use it for different wavelengths / put different gratings in. 26-Jan-20 07:29 PM If instead of a CCD, you have an output... Ta-da, monochromator 26-Jan-20 07:29 PM On their sales page they say "monochromator/spectrometer" 26-Jan-20 10:05 PM @ZeptoBars ah awesome - I'm also playing with a hybrid of a volume grating and a planar one 26-Jan-20 10:05 PM ah and with a hybrid using AOM in the cavity 26-Jan-20 10:05 PM but no success so far 26-Jan-20 10:05 PM I guess I'll stick to piezo tuned 26-Jan-20 10:05 PM what kinda works is using the aom as the tuning element in the cavity between normal grating and ld 26-Jan-20 10:05 PM need to investigate further ... 26-Jan-20 11:31 PM @idmb yeah went to their website and clicked that section but they only seem to show monochromators from what I could tell 26-Jan-20 11:34 PM They have a slash 26-Jan-20 11:34 PM Look at the component diagrams 26-Jan-20 11:34 PM They take an input beam of light and show you the spectrum 26-Jan-20 11:34 PM It’s all monochromator/spectrometer because it’s the same 26-Jan-20 11:34 PM You get a Fourier plane at the ccd 27-Jan-20 05:36 AM Heeeeeeey. Just figured out how I'll modify that laser power meter 27-Jan-20 05:36 AM I'll remove that stub of a power cable and add in 2x these https://www.ebay.com/itm/1-YCL-DC-101-LAN-DC-DC-CONVERTER-ISOLATION-500V-POWER-IN-5V-OUT-9V-23-PIN-DIP-/322433942586 27-Jan-20 05:36 AM And a DC barrel socket at the input 27-Jan-20 05:36 AM tho 25kHz switching frequency will make it quite annoying to silence. But I have them right here on my desk. 27-Jan-20 05:36 AM So 2x of those and hooking it up where the split psu used to be. 27-Jan-20 05:36 AM Assuming it uses split psu and not 18V 01-Feb-20 05:48 PM https://media.discordapp.net/attachments/620087857129979914/663535156774043689/unknown.png?width=455&height=684 01-Feb-20 05:48 PM I found some really quite small laser welders from China that has average power down to 50W 01-Feb-20 05:48 PM <__ice9#6039> Anyway so flashlamp passive Q-switched YAGs tend to just blast a cloud of plasma off the surface instead of welding anything, even in tungsten 01-Feb-20 05:48 PM Flashlamp pumped Nd:YAG 01-Feb-20 05:48 PM <__ice9#6039> Huh interesting 01-Feb-20 05:48 PM <__ice9#6039> Maybe no Q-switch? 01-Feb-20 05:49 PM The pulse repetition rate is really low here 01-Feb-20 05:49 PM <__ice9#6039> Of course 01-Feb-20 05:49 PM Yeah not q-switched 01-Feb-20 05:49 PM <__ice9#6039> So each one makes a pancake 01-Feb-20 05:49 PM <__ice9#6039> Yeah that sounds right 01-Feb-20 05:50 PM Still not that affordable though. You may be able to retrofit this since the laser cavity itself is the same across all models below 500W (I think) 01-Feb-20 05:50 PM So you'd just put in a bigger power supply and maybe caps 01-Feb-20 05:53 PM <__ice9#6039> I have a lot of this stuff already actually, but the YAG crystal I have is too constrained by the reflector chamber (from a diode one with dead diodes, seller was getting rid of parts). I have a ruby rod but the caps aren't large enough (need like 1kJ). And then I have some kind of rangefinder rod, don't recall exact type atm but it's light green and labeled. 01-Feb-20 05:53 PM <__ice9#6039> I have diodes as well for that one 01-Feb-20 05:53 PM <__ice9#6039> For CW or passive Q-switch 01-Feb-20 05:53 PM <__ice9#6039> Ah right it's an erbium one iirc 01-Feb-20 05:55 PM Can you just replce the diode bars? 01-Feb-20 05:55 PM Since a lot of them are designed to be replaceable like this one 01-Feb-20 05:55 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/noirint-5ACE7.png 01-Feb-20 05:57 PM <__ice9#6039> Google any laser, you get this type of search results page lol 01-Feb-20 05:57 PM <__ice9#6039> Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/1580608546301-86E27.png 01-Feb-20 05:57 PM Ah the beauty industry 01-Feb-20 05:57 PM Biggest gift to the laser hobbyist in some time 01-Feb-20 05:58 PM <__ice9#6039> It's more complicated than that. I have actual unmounted diode bars. So they need to be packaged. But I have 1600W worth of them. So it is probably worth the trouble. The original YAG was 400W and cooling constraints mean not all could likely fit. So might need to machine additional ports into the reflector. Not sure. Not yet working on those. 01-Feb-20 06:00 PM https://www.youtube.com/watch?v=dTsZ299ljwY&feature=emb_logo 01-Feb-20 06:00 PM These guys made their own cooling plates to mount to these diodes and made their own side-pumped Nd:YAG set-up. Perhaps consider a supersized version of this? 01-Feb-20 06:00 PM With multiple water loops to cool all your diodes 01-Feb-20 06:03 PM <__ice9#6039> To assemble a quick flashtube pumped laser, I would connect my xenon flashtube to my 100uF 1500V capacitor, connect that to my adjustable variac-MOT 1kW HV PSU through a diode, connect the flashtube top to the 6kV flashtube ignitor I built with a coil and an SCR, and I guess maybe figure out how to wrap the mirror polished stainless steel sheets in my sheet metal bin into some kind of elliptical cylinder (?) not sure if a different material like Brashear silver is better (?) 01-Feb-20 06:03 PM <__ice9#6039> Oh haha yeah those need water cooling 01-Feb-20 06:03 PM <__ice9#6039> That's quite mandatory 01-Feb-20 06:03 PM <__ice9#6039> Yes copper blocks are easiest 01-Feb-20 06:05 PM Perhaps consider making your reflector chamber out of a big chunk of aluminum and polishing the inside would be easier? If you have a CNC then this is easy 01-Feb-20 06:05 PM For the flashlamp pumped laser 01-Feb-20 06:05 PM <__ice9#6039> Nope not for me, but actually hmm I could just plasma cut elliptical holes in a couple plates and stick the steel through them 01-Feb-20 06:05 PM <__ice9#6039> Question is whether it reflects well enough 01-Feb-20 06:09 PM It should be okay 01-Feb-20 06:09 PM Sam's Laser FAQ 01-Feb-20 06:09 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-8B015.png 01-Feb-20 06:11 PM <__ice9#6039> Huh neat 01-Feb-20 06:11 PM <__ice9#6039> Ok well that saves some trouble with gold then 01-Feb-20 06:11 PM <__ice9#6039> Silver tarnishes actually so that gets a bit dicey 01-Feb-20 06:11 PM <__ice9#6039> Impressive video -- definitely like the use of 8020 aluminum stock for alignment 01-Feb-20 06:12 PM You definetely don't want a dark spot and melting your reflector lol 01-Feb-20 06:12 PM <__ice9#6039> Decidedly 01-Feb-20 06:13 PM Actaully in longer lengths I don't know if I'd trust 8020 to be flat. Unless you have one of those fancy 5 axis adjustable optical mounts it may not be a long term solution 01-Feb-20 06:13 PM <__ice9#6039> It seems like diodes in larger YAG DPSS lasers are often mounted 120° apart around the YAG rod 01-Feb-20 06:14 PM Yeah and then for higher power they just extend the rod 01-Feb-20 06:14 PM <__ice9#6039> To avoid hitting each other 01-Feb-20 06:14 PM <__ice9#6039> Exactly 01-Feb-20 06:14 PM Or put multiple rods in the same cavity! 01-Feb-20 06:14 PM <__ice9#6039> Fast axis aligned with the rod also 01-Feb-20 06:14 PM <__ice9#6039> So yeah need a long rod for many 01-Feb-20 06:14 PM <__ice9#6039> I have 20 of them and they are about 1cm or a little longer 01-Feb-20 06:14 PM <__ice9#6039> So a normal YAG rod should work 01-Feb-20 06:15 PM At smaller pumping power going into each rod you can avoid thermal bifringerance while increasing the net beam output power 01-Feb-20 06:15 PM <__ice9#6039> Unfortunately this makes the mounting kind of annoying for current transfer 01-Feb-20 06:15 PM <__ice9#6039> Vs stacking diodes 01-Feb-20 06:16 PM Though the beam quality will degrade 01-Feb-20 06:16 PM <__ice9#6039> That sounds hard to align also, but I guess maybe just stick them together with some precise tubing 01-Feb-20 06:16 PM You can completely fill the radius of the rod with pump diodes 01-Feb-20 06:16 PM But at that point you might saturate it 01-Feb-20 06:16 PM You don't need precise alignment for the diode bars 01-Feb-20 06:17 PM <__ice9#6039> Huh 01-Feb-20 06:17 PM <__ice9#6039> I meant to avoid wasting diode power mainly 01-Feb-20 06:17 PM your only goal is to shove as much 808nm into a rod as you can 01-Feb-20 06:17 PM or, well, any light, really 01-Feb-20 06:17 PM but 808 works best 01-Feb-20 06:17 PM But watercooling packaging is the issue here 01-Feb-20 06:17 PM yep 01-Feb-20 06:17 PM you can make a yag rod lase by just shooting it into the sun 01-Feb-20 06:17 PM Unless you have a massive rod lol 01-Feb-20 06:18 PM <__ice9#6039> Yeah narrow angle radial layouts would start to require a lot of custom machining 01-Feb-20 06:18 PM <__ice9#6039> Lol magnifying glass pumped YAG 01-Feb-20 06:19 PM you joke, but that's pretty much what single side lamp pumped lasers are 01-Feb-20 06:19 PM I'd be interesting to see how large of a reflector/focusing lens you need to make a tiny YAG rod lase under the sun 01-Feb-20 06:20 PM yag lasers used regular xenon lamps(non flashy) prior to DPSS 01-Feb-20 06:20 PM so just have to do the math on that 01-Feb-20 06:21 PM <__ice9#6039> 500-1000W/m2 typical solar power density at the surface 01-Feb-20 06:21 PM <__ice9#6039> Depends on local weather etc 01-Feb-20 06:21 PM <__ice9#6039> 5800K is actually more favorable for 808nm than xenon 01-Feb-20 06:21 PM <__ice9#6039> Need to integrate the Planck function for this though, tedious to specify correctly 01-Feb-20 06:21 PM <__ice9#6039> Call it about 8% 01-Feb-20 06:21 PM <__ice9#6039> So 40-80W of usable pump light per m² 01-Feb-20 06:28 PM The thing is most of that light will be escaping the cavity unless you do some pretty clever arrangement of these reflectors 01-Feb-20 06:28 PM <__ice9#6039> We know green DPSS laser pointers use YAG 01-Feb-20 06:28 PM Due to the need for sun exposure 01-Feb-20 06:29 PM <__ice9#6039> So at under 100mW I suspect an ordinary magnifying glass may work 01-Feb-20 06:29 PM <__ice9#6039> But a tiny crystal would be needed 01-Feb-20 06:29 PM <__ice9#6039> An ordinary magnifying glass would focus about 500mW pumping light 01-Feb-20 06:29 PM <__ice9#6039> Based on estimates above 01-Feb-20 06:31 PM Then comes the challenge to confine that inside the reflector. For this reason end-pumping is probably not possible 01-Feb-20 06:31 PM Since most of the pumping light would just go straight out the other side 01-Feb-20 06:32 PM <__ice9#6039> Lol yes, most likely 01-Feb-20 06:32 PM <__ice9#6039> I haven't ever seen an end-pumped YAG 01-Feb-20 06:32 PM <__ice9#6039> But the laser pointer ones I think use that config 01-Feb-20 06:32 PM <__ice9#6039> Let's see 01-Feb-20 06:32 PM <__ice9#6039> Oh hmm that's actually pretty common yes 01-Feb-20 06:32 PM <__ice9#6039> Idk no reflector here 01-Feb-20 06:32 PM <__ice9#6039> Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Green_Laser_cutaway_341px-D9FE2.jpg 01-Feb-20 06:32 PM <__ice9#6039> Just put it directly onto the crystal faces instead 01-Feb-20 06:36 PM This is doable at a high power too 01-Feb-20 06:36 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Compact_high-power_end-pumped_NdYAG_laser-30DDF.pdf 01-Feb-20 06:36 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-38241.png 01-Feb-20 06:37 PM <__ice9#6039> Ah that would be neat for making use of fiber coupled pumps 01-Feb-20 06:37 PM <__ice9#6039> I have a couple though not in the best condition 01-Feb-20 06:37 PM <__ice9#6039> Old = half dead 01-Feb-20 06:37 PM <__ice9#6039> But running 01-Feb-20 06:38 PM Wonder where you can get those mirrors they used in the paper 01-Feb-20 06:38 PM Even the tiny laser pointer thing has a reflector 01-Feb-20 06:38 PM <__ice9#6039> Yeah integral one 01-Feb-20 06:41 PM 1064/808 dichroic? 01-Feb-20 06:42 PM If you just have the diode bars this could be a nice way of end-pumping the YAG rod 01-Feb-20 06:42 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-D1C9A.png 01-Feb-20 06:42 PM @idmb Yeah, at a high power and resonable cost 01-Feb-20 06:44 PM <__ice9#6039> Those sound very similar to my diode bars 01-Feb-20 06:44 PM Let me give you the full paper here 01-Feb-20 06:45 PM <__ice9#6039> Making that prism array would be challenging though 01-Feb-20 06:45 PM Easier than fiber coupling them yourself 01-Feb-20 06:45 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Efficient_NdYAG_laser_end_pumped_by_a_high-12DAE.pdf 01-Feb-20 06:45 PM <__ice9#6039> I feel like side pumping is probably easier 01-Feb-20 06:46 PM SWP-45-RP1064-TU700-900-PW1-1012-UV $210 each 01-Feb-20 06:46 PM That's not affordable lol 01-Feb-20 06:46 PM But okay now that I know it can be done I will keep looking 01-Feb-20 06:46 PM <__ice9#6039> Ah these are only 10W bars 01-Feb-20 06:46 PM <__ice9#6039> Mine are 80W x___x much more cooling needed 01-Feb-20 06:47 PM How long is your YAG rod? Only able to accomodate one diode bar in length? 01-Feb-20 06:47 PM <__ice9#6039> Oh, yeah all kinds of dichroic laser optics are available 01-Feb-20 06:47 PM <__ice9#6039> Hmm it's idk like 8cm long 01-Feb-20 06:47 PM <__ice9#6039> I think about 3mm diameter as you wrote 01-Feb-20 06:47 PM <__ice9#6039> Yeah that sounds right 01-Feb-20 06:49 PM Have you checked the transmission through the back of your normal mirrors? 01-Feb-20 06:49 PM Transmission of 808nm? I don't know, probably quite high 01-Feb-20 06:49 PM When you don't care about polarization, you get a lot of options 01-Feb-20 07:47 PM https://youtu.be/aQurnodg3T4 01-Feb-20 07:47 PM This is incredibly cool 01-Feb-20 07:47 PM Using a pulsed laser to dynamically balance something spinning at 48krpm 01-Feb-20 07:47 PM @Mason_Yu we totally have to try this 01-Feb-20 07:55 PM Hmm, to measure where the rotors are out of balance can you use one fast accelerometer in one axis only? 01-Feb-20 07:55 PM Seems pretty complicated to do this in general for multiple planes 01-Feb-20 07:55 PM Looks like they use some sort of laser thing 01-Feb-20 07:56 PM Isn't that just a tachometer? 01-Feb-20 07:56 PM could be 01-Feb-20 07:56 PM there are lots of ways to measure vibration 01-Feb-20 07:56 PM The vibrations would be on the order on microns 01-Feb-20 07:56 PM Perhaps a capacitive sensor would be better 01-Feb-20 07:56 PM Also I don't plan on balancing tons of rotors, the efficiency improvement with using a laser doesn't make a huge difference to me 01-Feb-20 07:58 PM it's the precision 01-Feb-20 07:58 PM What I do want to do is balance some of the crankshafts for the motorcycle engines 01-Feb-20 07:58 PM you can adjust live 01-Feb-20 07:58 PM balancing motorcycles is way too coarse here 01-Feb-20 07:58 PM Yeah 01-Feb-20 07:58 PM The other potential application is rebuilding high speed chinese watercooled spindles 01-Feb-20 07:58 PM Ones that reach up to 40K rpm with >2kW power 01-Feb-20 07:58 PM But they are usually quite good already out of the factory and I don't expect to really improve them 01-Feb-20 07:58 PM Actually most of the vibrations probably comes from cheap collets or tool holders 01-Feb-20 08:10 PM I don't recall which mfg but I had recently come across a patent for the in-situ ablative balancing applied for turbomolecular pump rotors. Probably pfeiffer since I was trying to dig up info on my totally-not-documented TPH-1500 pump 01-Feb-20 08:10 PM I think it's for magnetic bearing pumps 01-Feb-20 08:11 PM Could have been. Totally wasn't describing my pump that's for sure 01-Feb-20 08:18 PM related: leybold literally would not send me PDFs of the manuals of the pumps we had just bought. They said I was free to scan the paper copies they sent 02-Feb-20 07:36 AM <__ice9#6039> @idmb post them online 02-Feb-20 07:36 AM <__ice9#6039> just send them to a bunch of relevant datasheet websites and maybe dump onto scribd (awful pyramid scheme site but worth including anyway) 02-Feb-20 01:57 PM just learned from the nametag on my recent gauge block set came from a german machinist from Leitz microscopes, when based out of NJ 02-Feb-20 01:57 PM the gauge blocks are also german (Hommel) 02-Feb-20 10:31 PM https://twitter.com/profanegeometry/status/1224215093073702913?s=19 new laser 02-Feb-20 10:31 PM joins @Spirit in the unnecessarily large HeNe corner 02-Feb-20 10:32 PM Congratulations 02-Feb-20 10:32 PM Mine is still bigger(har har ) 02-Feb-20 10:32 PM but congratulations 02-Feb-20 10:32 PM Have you managed to re-lase your dead tube? 02-Feb-20 10:41 PM mine's older 02-Feb-20 10:41 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-29280.png 02-Feb-20 10:42 PM https://i.imgflip.com/3o0bgg.jpg 02-Feb-20 10:42 PM FWIW if you have it benched, just using ND filters to make it barely visible is IMO nicer than goggles 02-Feb-20 10:42 PM lol I'd need to get PPE too though so eh 02-Feb-20 10:42 PM someday 02-Feb-20 10:44 PM a big pile of ND filters sounds appropriate and reasonable actually tbh 02-Feb-20 10:44 PM actually already have some, too, thanks photography hobby impulse purchases 02-Feb-20 10:45 PM reflective or absorbing? 02-Feb-20 10:46 PM @Spirit nah, tried re-diffusing it but still couldn't get it to lase. i think it had a misaligned capillary, so i.. took it apart to examine 02-Feb-20 10:46 PM tons of weird sputter damage inside it sure didn't help matters 02-Feb-20 10:46 PM A common use for them is to protect a beam profiler / CCD that's being used to overlap the focii of multiple beams, which often ends up involving accidentally burning a hole in the ND filter which makes it useless for safety. So I have to hide my hene ones from the rest of my lab -_- 02-Feb-20 10:46 PM alas, all of $2 down the drain 02-Feb-20 10:46 PM they're (very cheap) absorbing ND filters, i'd guess 02-Feb-20 10:47 PM but, a 600-700nm Hene you can't see is not one that's likely to damage your eyes 02-Feb-20 10:47 PM *properly functioning, that is 02-Feb-20 10:47 PM absorbing ND filters can burn, probably not with a hene but... eh 02-Feb-20 10:57 PM def. worth keeping an eye out for.. could see if the thermal camera has anything to say about it 02-Feb-20 10:58 PM I have a 26mW hene @idmb 02-Feb-20 10:58 PM it can burn 02-Feb-20 10:58 PM first step is powering the thing though 02-Feb-20 11:20 PM <__ice9#6039> Yeah I wouldn't trust a device-local filter, though HeNe tends to be only a few mW which is not much of a hazard 02-Feb-20 11:30 PM <__ice9#6039> I have found it manageable to stick with my rule of never running anything above 1W in the same room as myself. 02-Feb-20 11:30 PM <__ice9#6039> Also a pair of supposedly-OD7+ goggles in each relevant wavelength range for everything else + any backscatter around walls. I know some people disagree about which brands to trust-- I tested them with a camera and they do seem to work, but to each their own. 02-Feb-20 11:30 PM <__ice9#6039> @qualia re: powering them, I have used those little cheap ionizers on eBay to do so successfully. If the capillary tube is broken, though, then there will be problems. 02-Feb-20 11:38 PM reflective ND filters aren't at risk from a hene 02-Feb-20 11:38 PM <__ice9#6039> I agree 02-Feb-20 11:38 PM the reflections are if you just plop them in randomly, of course 02-Feb-20 11:38 PM yeah CW they can take like 10W/cm^2 02-Feb-20 11:38 PM (thorlabs BK7) 02-Feb-20 11:41 PM <__ice9#6039> Yeah that's not much unless it's after a beam spreader 02-Feb-20 11:41 PM IDK, to each their own. Obviously safest is goggles + filters, the human element is going to matter a lot more 02-Feb-20 11:41 PM <__ice9#6039> Or an unusually fat crystal hmm 02-Feb-20 11:41 PM <__ice9#6039> Oh yeah like I said I agree 02-Feb-20 11:41 PM <__ice9#6039> Merely pondering use cases 02-Feb-20 11:44 PM Hene beams are tinier than I thought, but even at 100um diameter you're at an 80mW hene 02-Feb-20 11:44 PM and I think most are closer to 1mm? 02-Feb-20 11:45 PM <__ice9#6039> Huh interesting they use Inconel to coat them https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=119 02-Feb-20 11:45 PM <__ice9#6039> Yeah HeNe is not an issue at all 02-Feb-20 11:45 PM <__ice9#6039> Diode """pointers""" and similar are 02-Feb-20 11:45 PM I mean it's closer to an issue than I thought 02-Feb-20 11:45 PM I thought they were more of a 1mm beam 02-Feb-20 11:45 PM <__ice9#6039> Yep 02-Feb-20 11:46 PM but buying one that's 0.5mm is easy 02-Feb-20 11:47 PM <__ice9#6039> Conservation of etendue is rather interesting-- spreading out the beam to make it diverge less 02-Feb-20 11:48 PM yes 02-Feb-20 11:48 PM and the whole 02-Feb-20 11:48 PM lasers not focusing to a point 02-Feb-20 11:48 PM so with diode pointers your beam is diverging a ton but starts tiny? 02-Feb-20 11:50 PM <__ice9#6039> Yes 02-Feb-20 11:50 PM everything I've got is optimized for good collimation, haha 02-Feb-20 11:50 PM and the beams have to be quite large to not destroy mirrors 02-Feb-20 11:50 PM (or the air) 02-Feb-20 11:50 PM Then yes, sticking filters on the output is a terrible way to be safe 02-Feb-20 11:51 PM <__ice9#6039> They are actually pretty bad in terms of beam quality, usually used either with a focusing lens to make them etch things, or with a defocusing lens to make them less dangerous 02-Feb-20 11:51 PM <__ice9#6039> Or beam spreader which also somewhat does 02-Feb-20 11:51 PM <__ice9#6039> They're too weak to do most materials processing and too strong to simply appreciate for aesthetic value, though 02-Feb-20 11:53 PM henes are basically just alignment aids irl 02-Feb-20 11:53 PM useless for me because I had gratings that needed aligning for 800nm 02-Feb-20 11:53 PM <__ice9#6039> Hmm yes, also useful for highly stabilized output in certain experiments 02-Feb-20 11:53 PM <__ice9#6039> Ah yeah 02-Feb-20 11:54 PM I don't really know of much use outside teaching experiments 02-Feb-20 11:54 PM which they're great for 02-Feb-20 11:54 PM <__ice9#6039> Hmm goodnight 02-Feb-20 11:56 PM gn o/ 02-Feb-20 11:56 PM i'm curious about using mine for imaging 02-Feb-20 11:56 PM laser schlieren, etc 02-Feb-20 11:56 PM perhaps an attempt at interferometry 02-Feb-20 11:56 PM mostly Learning How To Laser 03-Feb-20 12:30 AM HeNe are also good references for spectroscopy 03-Feb-20 12:30 AM I'm using them for spectroscopy interferometers 03-Feb-20 12:30 AM (because I have no alternative ) 03-Feb-20 12:51 AM just wanted to say that I like HeNe 03-Feb-20 07:10 AM not as good as lamps though 03-Feb-20 07:57 AM +1 on lamps, and can get hollow cathode lamps of varying gases darn cheap on eBay these days 03-Feb-20 07:57 AM HeNe is useful as it's a relatively cheap visible source with narrow linewidth and decent coherence length. But you can find really good bargains on DFB or FBG fiber coupled lasers in telecom wavelengths as well if visible spot isn't a requirement. 03-Feb-20 08:37 AM Oh I forgot that the linewidth makes it good for Raman microscopy 03-Feb-20 08:37 AM That’s probably the main research use 03-Feb-20 09:29 AM ok how to measure distance with lamps? 03-Feb-20 09:29 AM I mean a HeNe as a reference for spectroscopy 03-Feb-20 09:29 AM you need one reference 03-Feb-20 09:29 AM that's y most wavemeters are using HeNe lasers as a reference 03-Feb-20 09:29 AM every interferometer needs a reference 03-Feb-20 09:29 AM even if you want to use an optical frequency comb you need a reference for the beat frequency counting 03-Feb-20 09:29 AM that's y HeNe are still the heart of HiFi optics 03-Feb-20 09:29 AM "lamps" 03-Feb-20 09:29 AM thing is most people are using stuff like https://www.highfinesse.com/en/wavelengthmeter/wavelengthmeter-further-information/product-brochure-wavelengthmeter.pdf 03-Feb-20 09:29 AM without any clue how it works 03-Feb-20 09:29 AM just another USB device ^^ 03-Feb-20 09:29 AM everyday some dude comes along saying we don't need HeNe anymore because we have a wavemeter :)) 03-Feb-20 09:29 AM c'mon guys 03-Feb-20 10:42 PM not? 03-Feb-20 10:42 PM I super like HeNe 03-Feb-20 10:42 PM they're friends 03-Feb-20 10:42 PM ok the needed HV kinda sucks - but only for practicality 03-Feb-20 10:51 PM definitely has its place, I have a few along with kineflex fiber coupling assemblies so they're not so darn cumbersome 03-Feb-20 10:51 PM for interferometry I don't use any active reference, but I do use various hollow cathode lamps for calibration and such.. though I don't have no fancy schmancy HighFinesse equipment, just some home-brew all-fiber scanning michelson fourier type setups 03-Feb-20 10:51 PM butterfly packaged diodes and a peltier for closed loop temp seem to keep me plenty stable for the stuffs I do 03-Feb-20 10:58 PM but also then you need a reference to lock on 03-Feb-20 10:58 PM your laser diode 03-Feb-20 10:58 PM like a vapor cell 03-Feb-20 10:59 PM nope 03-Feb-20 11:00 PM hmmm whats the accuracy then? 03-Feb-20 11:01 PM in which metric? 03-Feb-20 11:01 PM frequency or wavelength 03-Feb-20 11:02 PM as in how stable is the laser? or how well I can resolve a laser under test, or? 03-Feb-20 11:02 PM both 03-Feb-20 11:02 PM at least you need enough stability to make sane scan cycles 03-Feb-20 11:03 PM scan cycle as in path length modulation? 03-Feb-20 11:03 PM the scanning is done with a piezo cyclinder at resonance, so pretty consistent from one sweep to another 03-Feb-20 11:03 PM that scan signal is probably what you would consider my reference, it's just in a different domain until it gets transformed 03-Feb-20 11:09 PM yeah it's similar to the normal michelson I have 03-Feb-20 11:09 PM in resonance the Q of the resonator matters 03-Feb-20 11:09 PM if you don't have a stable reference 03-Feb-20 11:09 PM so you measure the resonator frequency during the scan - maybe youre are using a adpll? 03-Feb-20 11:09 PM all digital bedause the f_r is pretty low and you have all the data for free 03-Feb-20 11:09 PM but besides that, what's the accuracy and resolution? 03-Feb-20 11:12 PM I just use the magic of a software defined radio that already handles things and trick it with a photodetector as an antenna 03-Feb-20 11:13 PM I mean I once tried a similar thing with a larger piezo actuated cavity 03-Feb-20 11:14 PM not sure honestly, at least in terms of normal specs.. I definitely trust it down to, hell I dunno.. I'd say 1/10th of a nm for OSA usage which has been my primary purpose 03-Feb-20 11:14 PM but my results were not so good 03-Feb-20 11:14 PM ah ok 03-Feb-20 11:15 PM I have been primarily going for sampling rate as I'm measuring rapid dynamic changes moreso than fine changes 03-Feb-20 11:15 PM yeah okay I guess that's feasible 03-Feb-20 11:15 PM no need for a I2 stabilzed HeNe then 03-Feb-20 11:16 PM nope, I'm not doing metrology, but I do think you under-estimate a fiber bragg grating or distributed feedback laser diode's stability 03-Feb-20 11:17 PM how? 03-Feb-20 11:17 PM not to mention I have 0 bulk elements 03-Feb-20 11:17 PM I don't under estimate them 03-Feb-20 11:17 PM I only know that I need to tune them 03-Feb-20 11:17 PM Currently I'm using external cavities 03-Feb-20 11:18 PM some day I will rent a proper wavemeter or OSA and measure some of my stuffs 03-Feb-20 11:18 PM for like 100kHz linewidths 03-Feb-20 11:18 PM with a normal reflective bragg grating 03-Feb-20 11:18 PM and I would use fiber bragg gratings 03-Feb-20 11:18 PM if that were possible with < 1MHz linewidths in the frequence range I need 03-Feb-20 11:20 PM you have any issue with vibration or thermal mass and whatnot? 03-Feb-20 11:20 PM of course I have 03-Feb-20 11:20 PM aside from the obvious alignment things, those are both things I also wanted to avoid 03-Feb-20 11:20 PM having a physically impervious assembly is nice when you have a cluttered lab lol 03-Feb-20 11:21 PM but I need narrowish linewidths 03-Feb-20 11:21 PM if a FBG would do the job, perfect 03-Feb-20 11:21 PM but haven't seen it yet 03-Feb-20 11:21 PM I know it's kinda possible to make your own FBG 03-Feb-20 11:23 PM it's difficult if you want to avoid the cladding as you need a femto 03-Feb-20 11:23 PM long period gratings are doable with run of the mill stuff though, and you can still do a bit with those like notch filters and the like 03-Feb-20 11:24 PM yeah 03-Feb-20 11:24 PM but I need a pretty narrow line width 03-Feb-20 11:24 PM < 1MHz is pretty hard for a FBG right? 03-Feb-20 11:24 PM especially in the near UV range 03-Feb-20 11:25 PM the standard procedure these days is a femto ytterbium or ti:sapphire and focusing a phase mask into the core so multiphoton absorption in the core and leavse the cladding untouched 03-Feb-20 11:25 PM not sure what the record holders are on that side, I'm currently using DFB telecom units.. I do want to mess around with writing some soon though 03-Feb-20 11:26 PM what's the current bandwith limit for FBG? 03-Feb-20 11:26 PM I know they can be stacked also fwiw 03-Feb-20 11:27 PM + not very practical for U 03-Feb-20 11:27 PM V 03-Feb-20 11:27 PM and then loss kicks in 03-Feb-20 11:28 PM not especially impractical either, so long as you can make the birefringence change in whatever fiber.. naturally a uv specific fiber will be more difficult to damage with.. uv .. to make said biref change 03-Feb-20 11:28 PM but if it would work it would be much more stable of course 03-Feb-20 11:28 PM yep 03-Feb-20 11:28 PM I think technically the bw limit is going to be more a limit on what the fiber can absorb and how much your source can put out 03-Feb-20 11:29 PM it's like inventing a technology that's currently not available 03-Feb-20 11:31 PM it would be nice also just to make a narrowly spaced comb 03-Feb-20 11:31 PM for that sort of thing I would mess with sub-wavelength fiber tapers though, as fun stuff can happen there 03-Feb-20 11:38 PM yeah 03-Feb-20 11:38 PM it would be possible to use a telco dfb laser with two stages of SHG 03-Feb-20 11:38 PM but after I saw the bow tie cavities for the crystals 03-Feb-20 11:38 PM would need two of them 03-Feb-20 11:41 PM high harmonic generation these days is funny business 03-Feb-20 11:41 PM and the specifically poled crystals (to prevent dispersion) 03-Feb-20 11:41 PM I tell you, weird shiz happens when you send a beam down sub-wavelength diameter fibers 03-Feb-20 11:42 PM it looked to me that building a solid external cavity for a laser diode is pretty simple 03-Feb-20 11:43 PM shg with e.g. mg doped lnbo3 shouldn't need any special cavity beyond temp 03-Feb-20 11:43 PM lemme dig up the fiber taper shg paper 03-Feb-20 11:45 PM ok 03-Feb-20 11:45 PM for < 400nm 03-Feb-20 11:45 PM I should add that 03-Feb-20 11:46 PM unlikely to find anything specific to that range hehe, but the theory is the important part as it's a geometry or surface wave sort of situation rather than lattice asymmetry sort of situation 03-Feb-20 11:46 PM not sure what the record min diameter is, but that'd be your wall 03-Feb-20 11:46 PM and your power requirements ofc 03-Feb-20 11:47 PM and my bet is within the next 2 years the stuff I'm doing becomes obsolete because sony releases < 400nm VCSEL 03-Feb-20 11:48 PM yea there has been some development in that market lately 03-Feb-20 11:50 PM my primary intention is putting ion trap stuff with laser cooling into cubesat like form factors 03-Feb-20 11:50 PM ahhh 03-Feb-20 11:50 PM maybe more like 3*3 units 03-Feb-20 11:50 PM but in that range 03-Feb-20 11:51 PM optical molasses sorta stuffs? doppler cooling? 03-Feb-20 11:51 PM doppler/side-band yes 03-Feb-20 11:51 PM very cool 03-Feb-20 11:51 PM grrr, this IS NOT it but I gotta paste something or I'm going to rage https://www.osapublishing.org/josab/abstract.cfm?uri=josab-27-8-1504 03-Feb-20 11:53 PM hmm 03-Feb-20 11:54 PM This is more on point https://ieeexplore.ieee.org/abstract/document/5500105 03-Feb-20 11:54 PM what are your requirements if you don't mind sharing? wavelength, linewidth and a general feel for flux? cw a requirement? 04-Feb-20 12:13 AM https://www.osapublishing.org/oe/abstract.cfm?uri=oe-13-18-6798 is probably the best jumping off point for the subject 04-Feb-20 12:45 AM thanks! looks interesting 04-Feb-20 08:31 AM I wish they made FBG that could take high power beams 06-Feb-20 03:40 AM So have people got those YAGs working now? 06-Feb-20 12:25 PM Hey @idmb , just noticed this channel exists 06-Feb-20 12:25 PM I'm not frequently active here, but want to be considerate in case I'm too on-topic in off topic 06-Feb-20 12:26 PM seems perfectly on topic 06-Feb-20 12:26 PM I'll be looking into what a waveplate is 06-Feb-20 12:27 PM haha 06-Feb-20 12:27 PM @idmb I'll be headed back down into the clean room hopefully again this afternoon, if not tomorrow 06-Feb-20 12:27 PM I'll try and sketch out a lot of what the system looks like, if this seems like a fun puzzle to solve 06-Feb-20 12:27 PM if your retros are 2 or 3 mirror rather than plane mirrors 06-Feb-20 12:27 PM then there is quite a bit of alignment to do 06-Feb-20 12:28 PM The splitter cubes have between zero and two can things sticking off the sides 06-Feb-20 12:29 PM a plane mirror reflects the beam at the angle of incidence from the same spot, a 2 mirror retro reflects it at a different position (determined from distance to vertex) and at a different angle in one plane, but at the same angle in another plane, a 3 mirror retro reflects it at exactly the same angle but shifted in X and Y from the vertex 06-Feb-20 12:29 PM the can things are the retros I believe 06-Feb-20 12:30 PM Ah, well I'll have to see what the model numbers are on those retros 06-Feb-20 12:30 PM https://www.bmisurplus.com/products/dp077-hewlett-packard-10703a-retroreflector-1st-grade 06-Feb-20 12:30 PM looks like they're the multi-mirror type 06-Feb-20 12:31 PM Well those are pretty 06-Feb-20 12:32 PM industry seems to call them cube-corner retros 06-Feb-20 12:32 PM Reminds me of the first time seeing Anamanaguchi live, and they had these iridescent/mirror/translucent/acrylic cubes https://vimeo.com/101175412 06-Feb-20 12:32 PM Well alright, I'll look at getting a solid description of the system put together and move towards figuring out alignment 06-Feb-20 12:34 PM alignment should be not too bad 06-Feb-20 12:34 PM it's just easier if you know what the stuff does 06-Feb-20 12:34 PM Yeah, I'm just bummed we have to do it 06-Feb-20 12:34 PM The laser itself got bumped last week 06-Feb-20 12:34 PM And the person working on the system decided to remove all the beam splitters and receivers for some reason 06-Feb-20 12:34 PM does your laser point directly into the beam splitter 06-Feb-20 12:34 PM or do you have some mirrors for steering 06-Feb-20 12:35 PM Straight into a beam splitter, and then one split goes into another splitter 06-Feb-20 12:35 PM There's 1 y direction measurement interferometer/receiver, and two x stage measurement combos 06-Feb-20 12:35 PM So two splits gives everything 06-Feb-20 12:37 PM seems like removing the splitter, then aligning the straight-through portion would be a start 06-Feb-20 12:37 PM that way, like I said, there's no interference to reduce your signal strength on the meter 06-Feb-20 12:38 PM well you can just block the other retro 06-Feb-20 12:38 PM Hmm 06-Feb-20 12:38 PM you can't do it with the splitter removed I don't think, isn't your signal from the splitter? 06-Feb-20 12:38 PM well but you might block it at full interference, right? 06-Feb-20 12:38 PM There's one straight through path 06-Feb-20 12:38 PM Then that's split off for the other two 06-Feb-20 12:39 PM unless you have a voice coil to wobble/pulse the measurement arm 06-Feb-20 12:39 PM but then you need the voice coil freq to be less than your detector bandwidth 06-Feb-20 12:39 PM I don't follow 06-Feb-20 12:39 PM and it makes it less easy than "maximize signal at the detector, means it's aligned as best as we can get" 06-Feb-20 12:40 PM alignment to the detector isn't the problem 06-Feb-20 12:40 PM colinearity of the two beams before the detector is 06-Feb-20 12:40 PM It's just that for the first time, since perhaps 1974, all of these optical bits were loosened 06-Feb-20 12:40 PM well if ALL the screws are gone, seems like aligning the straight path IS important 06-Feb-20 12:40 PM you get a much better interference signal if you have two beams colinear than if you just point them at the same spot 06-Feb-20 12:41 PM I mean, it's at least a start 06-Feb-20 12:42 PM Moving the retros in the plane perpendicular to the propagation axis of the beam that hits them 06-Feb-20 12:42 PM will shift the reflected beam 06-Feb-20 12:42 PM for this to work, they should be positioned just such that both beams upon reflection are hitting the same spot on the beam splitter, and the component that propagates to the detector should be travelling at the same angle 06-Feb-20 12:45 PM Well, with the retros, they're parallel but not coincident 06-Feb-20 12:46 PM What do you mean? 06-Feb-20 12:49 PM The beams 06-Feb-20 12:49 PM I'm not sure that they'll hit the same spot on the splitter 06-Feb-20 12:49 PM If they're not coincident 06-Feb-20 12:49 PM But maybe I'm misunderstanding, or mis-picturing the system 06-Feb-20 12:56 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-A8CF9.png 06-Feb-20 12:56 PM here's an interferometer 06-Feb-20 12:56 PM see how the position the beams hit R1 and R2 are different distances from the vertex? and how that means the 2 and 1 beams aren't colinear at the top / output? 06-Feb-20 01:03 PM Yeah for sure 06-Feb-20 01:03 PM So if that happens, then they're not going to be coincident at the splitter 06-Feb-20 01:03 PM And it happens 06-Feb-20 01:25 PM so this really isn't that bad 06-Feb-20 01:25 PM just get the source hitting the splitter at a good angle 06-Feb-20 01:25 PM and the adjust one retro to match the other 06-Feb-20 03:34 PM Good news, and thanks for the tips 06-Feb-20 03:34 PM We'll be at it in the morning 07-Feb-20 12:06 AM waitin for my fizeau 07-Feb-20 02:44 PM @tokyodrip any luck? 07-Feb-20 03:15 PM Got some tiny 1x1mm SiPM sensors to play with 07-Feb-20 03:15 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-EDD6A.jpg 07-Feb-20 03:15 PM Do report on the results 07-Feb-20 03:15 PM It's pretty hard to buy ketek sipms 07-Feb-20 03:17 PM Hard? 07-Feb-20 03:17 PM ooh 07-Feb-20 03:17 PM Last time I asked(and I did *ask), their webstore only shipped to commercial 07-Feb-20 03:17 PM And they're not at any distributors 07-Feb-20 03:17 PM Oh, I just used my LLC and didn't have any problems. 07-Feb-20 03:17 PM Duh, an LLC 07-Feb-20 03:19 PM I'll be using them for a bio fluorescence system, no cool physics stuff. 07-Feb-20 04:57 PM <__ice9#6039> Useful trick, have done similar 07-Feb-20 05:49 PM Do you think it would be possible to sputter/deposit a dielectric optical filter directly onto the coverglass of an SiPM? 07-Feb-20 05:56 PM It's not glass, it's epoxy 07-Feb-20 05:56 PM But yes, it should be possible 07-Feb-20 06:02 PM Datasheet refers to it as glass 07-Feb-20 06:08 PM I'm not familiar with ketek, but others were optical epoxy 07-Feb-20 06:08 PM one way to check... scratch one :P 07-Feb-20 06:08 PM I'm sure I will accidentally at some point 07-Feb-20 06:08 PM or email them and ask for the exact material 07-Feb-20 06:08 PM "Index of Refraction of Glass Entrance Window 1.52 @ 430 nm" 07-Feb-20 06:09 PM I'd try sputtering 08-Feb-20 02:12 AM what do they do 08-Feb-20 05:30 AM they're silicon photomultipliers. Basically offer a nice dynamic range from single photon to hundreds 08-Feb-20 09:41 PM A college satellite I worked on was going to use a SiPM to detect gamma rays over lightning storms up in the atmosphere. Neat stuff. 08-Feb-20 09:42 PM dark lightning! 08-Feb-20 09:42 PM neat.. yea that phenomenon they'll be looking for is pretty crazy 08-Feb-20 09:42 PM https://www.youtube.com/watch?v=OBOolkHVG_Q 08-Feb-20 09:44 PM "Terrestrial Gamma Ray Flashes" they called them. 08-Feb-20 09:45 PM yea I like that name better 08-Feb-20 09:45 PM I've not heard of dark lightning, but I'd like to see. 08-Feb-20 09:45 PM Well, then they subdivide the different kinds of gamma flashes into things much more recognizable like "Elves" and "Dwarves" and "Rabbits" which is awfully uncanny.... 08-Feb-20 09:46 PM Sprites and Pixie territory 08-Feb-20 09:46 PM https://en.wikipedia.org/wiki/Sprite_(lightning) 08-Feb-20 09:48 PM Yeah, that kind of stuff. 08-Feb-20 11:07 PM <__ice9#6039> Those are gamma active? Interesting. I saw one, but only once. 08-Feb-20 11:07 PM <__ice9#6039> Huh weird. They seem overwhelmingly terrestrial, but often in coastal or very humid regions. The latter probably drives more powerful storms, but I have no idea why they seem more common over land than the open oceans. 08-Feb-20 11:07 PM <__ice9#6039> Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Screenshot_20200209-010939-F8C0B.png 08-Feb-20 11:07 PM <__ice9#6039> It is not clear why this would be more common over land than water either 08-Feb-20 11:07 PM <__ice9#6039> Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Screenshot_20200209-011109-3C4D4.png 10-Feb-20 02:34 PM It's an area of active research, for sure. Some people are committing spacecraft to it, but not enough, as I've been informed. 10-Feb-20 08:18 PM <__ice9#6039> Question for someone more experienced with fiber optics than me: 10-Feb-20 08:18 PM <__ice9#6039> I have a NIR pyrometer on order with an SMA 905 connector, but not the cable. The cable is solely for conveying light from the furnace to the pyrometer. It is not transmitting digital data, just light radiating from the hot furnace walls. 10-Feb-20 08:18 PM <__ice9#6039> The correct multimode cable appears to have fiber width 750 or 800μm, but could be as narrow as 600μm. This is just based on measurements from photographs of it and the known dimensions of the SMA 905 connector, as well as some knowledge of common fiber widths and those most often used in spectroscopy. So there is some uncertainty still. 10-Feb-20 08:18 PM <__ice9#6039> Documentation does not indicate the fiber diameter 10-Feb-20 08:18 PM <__ice9#6039> I will have the pyrometer in hand within a week or so for direct measurements of the input connector 10-Feb-20 08:18 PM <__ice9#6039> But anyway: 10-Feb-20 08:18 PM <__ice9#6039> If I were to attach a cable with a wider fiber, say 1mm instead of 600/750/800μm, would the same amount of light from the other end of the fiber end up reaching the pyrometer as if it had used the official cable? 10-Feb-20 08:18 PM <__ice9#6039> Geometrically, I suspect that it should, but I am not certain about things like back-reflections from the annular outer ring of the wider fiber's cross-section that does not match up against the narrower fiber in the device. 10-Feb-20 08:18 PM <__ice9#6039> I do know that the official cable is quartz and that there is no lens on the other end, just a flat flush termination-- so that is easy to match correctly. I just need to understand the implications of using a wider fiber than the one in the device. 10-Feb-20 08:39 PM <__ice9#6039> Hmm. This article makes it sound pretty much just proportional to the contact area mismatch. https://www.ecmag.com/section/systems/trouble-mismatched-fibers 10-Feb-20 08:39 PM <__ice9#6039> If that's the case, then any equal or slightly wider fiber will do. 11-Feb-20 06:14 AM @__ice9 Optically it is not equivalent. With any change of diameter you will certainly need to re-calibrate. For such non-imaging applications wider could work, but I would really prefer smaller fibers. Also, note that 1mm quartz fiber has fairly large minimum long-term bend radius, it is not very convenient. 600 or 400um are much easier to work with. Thorlabs sells such fibers for not very expensive. 11-Feb-20 06:14 AM @__ice9 What you also need to know is NA of the fiber. Whether it is regular glass-glass NA0.22 or ones with polymer cladding (up to NA0.49) 11-Feb-20 08:17 AM <__ice9#6039> @ZeptoBars thanks! 11-Feb-20 08:17 AM <__ice9#6039> In that case, I will just wait until the pyrometer arrives and measure it properly with a micrometer 11-Feb-20 08:17 AM <__ice9#6039> I believe it is glass-glass given the use case. 11-Feb-20 10:04 AM @Spirit any ideas where to acquire thin sheets of ruby crystals? 11-Feb-20 10:05 AM China probably really 11-Feb-20 10:05 AM something like microscope slides 11-Feb-20 10:05 AM made of ruby 11-Feb-20 10:05 AM Or ebay 11-Feb-20 10:05 AM What for? 11-Feb-20 10:05 AM random laser 11-Feb-20 10:05 AM Probably won't work 11-Feb-20 10:11 AM The idea was suggested by my supervisor as a more interesting ultrafast-pumped ruby laser 11-Feb-20 12:40 PM <__ice9#6039> Using a thin plate? 11-Feb-20 12:40 PM <__ice9#6039> What is the pump? 11-Feb-20 12:46 PM ultrafast 400nm 11-Feb-20 12:46 PM tunable 400nm, even. So 403nm or whatever the optimal is 11-Feb-20 12:46 PM the cavity is formed from a stack of microscope slides 11-Feb-20 12:46 PM with the gain medium in between two in the centre 11-Feb-20 12:51 PM oo 11-Feb-20 02:16 PM <__ice9#6039> Huh nice 11-Feb-20 02:31 PM well it's easy to get to fluoresce 11-Feb-20 02:31 PM time to try making a cavity I guess 11-Feb-20 08:19 PM @imdb femtosecond and other ultrafast lasers are annoying from a laser safety POV. First, enclose it as much as possible so that you don't even need to worry. Second, absorptive dyes are prone to bleaching, sometimes permanently, as the dyes saturate. Your OD of 7+ may suddenly drop to 2, perhaps never recovering. Thin film coated eyewear recommended. Third, if you're using the ultrafast system to make a supercontinuum system, you're no longer safe with the thin film style because that will only help with a fraction of the bandwidth. In short, they're tough to control short of box that bad dog up. 11-Feb-20 09:48 PM That doesn't work when you're the one working on it 11-Feb-20 09:48 PM OD8 with an IR viewer and turning the intensity down whenever doing alignment... But I'm still unsure if that protects from a 1% intenstiy hit 11-Feb-20 10:03 PM The nice(?) thing is that ultrafast has quasi-CW behavior at low power wrt biological tissues, but that this is a thresholded effect that varies with wavelength and pulse duration. It really isn't something you want to count on to save you. 11-Feb-20 10:03 PM Since you mentioned an IR viewer, I gather you're probably doing something with 780nm. Alignment power will also reduce the saturation effects which definitely helps. 11-Feb-20 10:05 PM 800nm 50fs 10mJ 1kHz and 800nm 120fs 15mJ 1KHz 11-Feb-20 10:05 PM also a pulse stretcher and amplifier making the former 100ps 50mJ 10Hz 11-Feb-20 10:05 PM our instructions were basically a bunch of things not to do and "goggles help enough to wear them, but only against glancing reflections..." 11-Feb-20 10:08 PM Not gonna lie, with a laser like that the whole point of those gogs with a direct hit is to give you a chance to get your face the heck out of the way before burnthru. 11-Feb-20 10:08 PM They're mainly for scatter and partial (like .01%) specular reflections. 11-Feb-20 10:09 PM #1 instruction is definitely "keep the laser in a plane parallel to the optical table, and no shiny things anywhere near it unless intentional" 11-Feb-20 10:11 PM When you take the party up to a 1.2J/pulse, I assume suicidal ideation if you bring your head near the beam path. [1000 mile stare remembering my Quanta Ray engineers] 11-Feb-20 10:12 PM I'm pretty sure a direct hit through a regular silver/dielectric mirror from thorlabs would still do some damage 11-Feb-20 10:13 PM The good news is that part of the design spec for certified laser safety eyewear is that they will give you an auditory and visual warning during burnthrough. You will hear cracking and there will be flashing as the pulses hit. You will know. 11-Feb-20 10:13 PM There was a very good paper in November 2018 from NIST as they've finally started trying to typify the ultrafast bleaching and develop standards. I mean, this is a problem we've known about since the 1990s but we're only now starting to formally work on it. If you have spare Ti:Saph time you'd like to volunteer for NIST collaboration, they are happy to generate papers with anyone that wants to work with them. 11-Feb-20 10:16 PM we have a spare tisaph, tbh 11-Feb-20 10:16 PM ~15 year old spitfire with no oscillator 11-Feb-20 10:24 PM I'll have to see if I can find the paper and proposal tomorrow at work for you. 12-Feb-20 02:24 AM whatya toastin 12-Feb-20 09:29 AM So I'm trying to get a stupid powerful laser to fire, and I don't know if I should really, really be trying to use DI water, or if just distilled will be fine to cool this thing? Technically the water will be running across the silicon. 12-Feb-20 09:29 AM Should I really go for DI, or is distilled fine? 12-Feb-20 11:08 AM Distilled is fine 12-Feb-20 11:08 AM Make sure you have the right goggles or you're going to lose your eyes 12-Feb-20 11:12 AM if this is the laser i'm familiar with, don't even run it in open air. consider completely enclosing it in a box with a sacrificial webcam. also goggles yes 12-Feb-20 11:12 AM (playstation eye webcams are $1-$7, can go up to 320x240@187.5 FPS or 640x480@60+hz, and are IR-sensitive. sometimes local game stores have them sitting in boxes) 12-Feb-20 11:27 AM Raspberry pi + Ir cam is also a $20-30 option 12-Feb-20 01:09 PM Apparently I said a bad word? Anyways, yes, it's that laser, Qualia. Thanks for the tip on camera, I think I could try with a random CCTV camera and my pvm for a live feed. 12-Feb-20 01:10 PM there's a very aggro profanity filter, yeah 12-Feb-20 03:29 PM <__ice9#6039> Use a remote camera. If it's IR then the camera can see it better than you can in the first place. Cameras are very cheap. Even more so than goggles. If you can afford a laser then you can afford goggles. If you can afford goggles then you can afford cameras. 12-Feb-20 03:29 PM <__ice9#6039> Distilled water is fine. DI resin is pretty cheap but the difference matters more for long-term use. 12-Feb-20 03:29 PM <__ice9#6039> The beam spot from a high powered laser is a severe optical hazard in its own right and should never be viewed directly. Goggles help protect from the worst of it. They generally will not be reliable for direct hits, so be aware of any possible sources of beam reflections and be sure to run the device with a flat opaque backstop, preferably something like a roughened graphite block. 12-Feb-20 03:29 PM <__ice9#6039> A firebrick can also work reasonably well 12-Feb-20 03:29 PM <__ice9#6039> Temperatures on the backstop will be several thousand degrees during sustained beam exposure and material vaporization will occur, so be sure it is something refractory and not particularly toxic 12-Feb-20 03:29 PM <__ice9#6039> IR lasers at 1064nm and above, and pump diodes at 976nm are essentially invisible. 808nm is visible, but at an apparent level of brightness that is several orders of magnitude smaller than its actual brightness. 12-Feb-20 03:29 PM <__ice9#6039> I know this from experiments with optical filters and a 5W LED 808nm flashlight. Not from looking at actual laser diodes. 12-Feb-20 03:29 PM <__ice9#6039> In contrast, any typical cell phone camera or similar can correctly detect all of these wavelengths and display them with something pretty close to their true relative brightness 12-Feb-20 03:29 PM <__ice9#6039> https://twitter.com/__ice9/status/936072997571579906?s=19 12-Feb-20 03:29 PM <__ice9#6039> Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200212_174829-97BA9.jpg 12-Feb-20 03:29 PM <__ice9#6039> An 808nm NIR LED flashlight can be used as an actual flashlight given sufficiently dark-adapted eyes, but the view is rather... strange 12-Feb-20 03:29 PM <__ice9#6039> On a very bright and sunny day, it is also possible to use IR pass filters to view the entire local surroundings in NIR 12-Feb-20 03:29 PM <__ice9#6039> The result is very similar to examples of NIR camera photos. Some light colored buildings appeared black, as did the sky, while vegetation was pale 12-Feb-20 03:51 PM how many watts is "stupidly powerful" 12-Feb-20 03:51 PM like is that just a 100W fiber laser... or ? 12-Feb-20 03:53 PM <__ice9#6039> >just 12-Feb-20 03:53 PM <__ice9#6039> But yeah curious as well 12-Feb-20 03:53 PM <__ice9#6039> Hmm also, it's possible likewise to directly perceive UV-A. It needs some special filters to eliminate fluorescent emissions. The appearance is deep violet. 12-Feb-20 03:53 PM <__ice9#6039> Not suggested for any kind of prolonged period though. 12-Feb-20 03:56 PM 100W is still "pretty common" 12-Feb-20 03:58 PM 140 watt laser diode working at 940nm 12-Feb-20 03:59 PM laser slide? ahh. 12-Feb-20 03:59 PM that's pretty yikes 12-Feb-20 03:59 PM Hmm is that what non-flashlamp yags are pumped with? 12-Feb-20 03:59 PM nope, 880nm 12-Feb-20 03:59 PM oh great 12-Feb-20 03:59 PM the IR filter on my yag is pretty good 12-Feb-20 03:59 PM it lets out a small amount of IR 12-Feb-20 03:59 PM "<1W" 12-Feb-20 04:03 PM Nice, that's still considered class 4 12-Feb-20 04:03 PM How much cooling does your diode need? 12-Feb-20 04:03 PM like isn't that getting into "big annoying chiller" territory? 12-Feb-20 04:08 PM Well, the output is 140, and the stack needs 50 or so amps at 13 or so volts, for a total of 650 or so watts. So, ideally the chiller can pull away 500 watts of heat, or so the calculation goes. 12-Feb-20 04:10 PM and what's the temp sensitivity of the diode? 12-Feb-20 04:10 PM (temp delta helps with cooling, obviously ) 12-Feb-20 04:43 PM Ooh, that I don't know 12-Feb-20 05:06 PM @idmb Journal of Laser Applications, Vol 29, Number 4, November 2017 “Ultrafast laser eyewear protection: Measurements and precautions” by Stromberg, Hadler, Alberding and Heilweil. Joshua Hadler is the main NIST person wrangling this project. 12-Feb-20 05:09 PM -_- that's without an amplifier 12-Feb-20 05:09 PM RIP my eyes 12-Feb-20 05:19 PM +1 on cameras. any ol' webcam/ccd will do for that wavelength. Can also remove the IR cut filter from the camera if you want to increase sensitivity/framerate (reduce exposure). Literally like <$10/ea; buy a handful. 12-Feb-20 05:21 PM also useful for aligning focii 12-Feb-20 05:21 PM just fill it up with ND filters and scan with a telescope 12-Feb-20 05:26 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/FB_IMG_1530031335513-C2810.jpg 12-Feb-20 07:13 PM seeing a fiber glow 12-Feb-20 07:13 PM makes me uncomfortable 12-Feb-20 07:13 PM sheath pls 12-Feb-20 08:23 PM Yes pls 12-Feb-20 08:56 PM it is sheathed; at least coated.. attenuates plenty and nobody over my shoulders with a pair of scissors.. 12-Feb-20 08:56 PM this is it unpowered 12-Feb-20 08:56 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/tmp_1530031423939-C9E15.png 12-Feb-20 09:04 PM What kind of fiber is that? 12-Feb-20 09:04 PM uncertain 12-Feb-20 09:04 PM I'd guess in the vicinity of 10/125 12-Feb-20 09:04 PM if the mfg is obeying the color conventions then it should be 50/125 12-Feb-20 09:04 PM keep in mind the color you're seeing is just the camera being excited by the near-ir... which also penetrates like near-ir.. IRL you can't see any difference 13-Feb-20 05:12 AM <__ice9#6039> ... shouldn't be looking straight at that thing with eyes 13-Feb-20 05:44 AM Do not expose remaining eye to laser light. 13-Feb-20 06:20 AM Was wearing glasses and the entire point was just demonstrating how useful and SAFE using a camera to view the beam is. Context, people. Scroll up. 13-Feb-20 07:01 AM It was a joke :) 13-Feb-20 07:01 AM at-least what I said 13-Feb-20 07:11 AM <__ice9#6039> @ZeptoBars#7360 thanks for earlier advice on fiber diameter mismatch insertion loss. I received the pyrometer and found the internal window is a full 3mm across. Documentation I found subsequently noted that two-color IR pyrometers are actually immune to emissivity variation as they rely only on the ratio. This implies they are also immune to fiber diameter variation as the effect would be the same as variation in emissivity. Initial testing looked plausible. Still need to set up controller. 13-Feb-20 07:29 AM Sry did an all-nighter and overly testy and not so quick at thought. 13-Feb-20 09:16 AM nice image 13-Feb-20 08:14 PM So uhm, optics n00b wanting to ask n00bie questions So I am getting a UV LED to convert a DLP projector for litho... Ordered a 50W led array... Now the original DLP has the light go through a small hole then bounces off a mirror through a lens to the DLP at the incidence angle. Now I have two options here... Remove the mirror it bounces off of and put the LED right there, that mirror hole is basically just about the right size for the LED array, but I don't know how smooth/balanced the light will be that way... The other option is to get the light from the 20mmx20mm? array down through a like... 10mm diameter hole? What is the term for the thing I want to search for in the optics world to get that light focused down and going in one direction? I assume that would probably be two different pieces of optics... But yea I could swear I have heard the terms for some of this tossed around in the past but... I am n00b so help please experts? :) 13-Feb-20 08:19 PM Try non-destructively removing the mirror 13-Feb-20 08:19 PM oh its easy, its just screwed in with a backing plate I beleive 13-Feb-20 08:19 PM its not HARD, I just was wondering what extra light would be bouncing around coming off the light module like that 13-Feb-20 08:19 PM where as its intended to come from a 10mm diameter hole probably pretty... straight? light? like I dunno what the word is for straight light like that. Either way then go through the lens in there to the DMD 13-Feb-20 08:19 PM I can give that mirror removal a try its easy 13-Feb-20 08:19 PM but yea I am still waiting to receive it anyway, but once I do I will let you know how that goes 13-Feb-20 08:19 PM I am currently making a little atmega chip emulate the OSRAM bulb board to make the logic board happy and think there is still a bulb supply in there lol 13-Feb-20 08:23 PM Parallel, but no it can be quite random 13-Feb-20 08:24 PM ok cool, unfortunately the black paint on the inside of that chamber isn't quite vantablack... but yea we will see 13-Feb-20 08:24 PM I really need to ensure I don't have light bleed and have an EVEN light source for exposure to try and keep the adjustment via software down to a minimum to make my life easier 13-Feb-20 08:25 PM It will be vantadust after the suntan you're going to give it 13-Feb-20 08:25 PM ehh.... its barely UV... almost violet... but I think it will cure the stuff I want to try and use 13-Feb-20 08:25 PM not like its UV C lol 13-Feb-20 08:26 PM UV C leds are pretty weak still...thankfully? some cool uses for them i can think of but the safety implications are a bit concerning 13-Feb-20 08:26 PM but depends what specific led you got for if you need to worry about the other UV emissions too 13-Feb-20 08:27 PM again, I am using a UV A LED here so its not crazy but yea 13-Feb-20 08:27 PM its like... 396-400... seriously 13-Feb-20 08:27 PM its basically violet 13-Feb-20 08:27 PM but I believe people have used these to expose what I want to test with 13-Feb-20 08:27 PM and it was cheap so whatever 13-Feb-20 08:27 PM worth a shot 13-Feb-20 08:27 PM if not I do have stuff it'll expose and I'll use the LED in something else 13-Feb-20 08:28 PM yep i would not be worried about it just would still wear something like polycarbonate safety glasses (cheap UV filters) at the very least 13-Feb-20 08:29 PM yea I need to get some, but I ordered this slow boat so it'll be awhile before I get LEDs to play with lol 13-Feb-20 08:29 PM will get some decent glasses via amazon 13-Feb-20 08:29 PM I need some for another UV tool I have 13-Feb-20 08:29 PM https://photos.app.goo.gl/9qW9LLdyW7txgbB69 13-Feb-20 08:29 PM 100W UV... I want to say B/A? I believe... but I can't find a manual so I can't be sure... But yea through a light pipe from a mercury vapor lamp 13-Feb-20 08:29 PM its... scary... to say the least... 13-Feb-20 08:29 PM but MAN does it cure stuff! 13-Feb-20 08:29 PM and footswitch! 13-Feb-20 08:29 PM got it out of the trash from a place... 13-Feb-20 08:29 PM if and when I need to replace the bulb though... oof... like 300 bucks or so 13-Feb-20 08:32 PM ouch 13-Feb-20 08:32 PM only thing i have personally seen mercury vapor lamps used for besides lighting is collecting insects, that is some old school curing tech there... 13-Feb-20 08:32 PM does the foot switch operate a shutter or turn the bulb on/off? 13-Feb-20 08:33 PM there is a timer module on the left there 13-Feb-20 08:33 PM you can set down to like tenths of a second up to like a long time... 13-Feb-20 08:33 PM and you click it and it shutters it open for that long then closes or you can put it in manual mode where the footswitch directly operates it 13-Feb-20 08:33 PM its pretty nice 13-Feb-20 08:35 PM ahh okay i figured it had to be something like that with the bulb running continuously. hard to beat if you need really broad spectrum UV 13-Feb-20 08:35 PM just gotta let it warm up before you use it unlike LEDs 13-Feb-20 08:37 PM heh yea 13-Feb-20 08:37 PM I was thinking of just pumping that into the projector.... it would probably work GREAT, but I don't want to get that many hours on that expensive bulb... if I can use an LED like others have I'd love to do that instead 13-Feb-20 10:35 PM @Conmega is your led a cob sort of style? Any idea how many emitters are within the 20x20mm array? Are they placed symmetrically? The word you're looking for is "collimated" btw. The hole in the OEM optics path is likely serving as a spatial filter to help homogenize the light, acting as a point source of diameter D emitting a spherical wavefront. 13-Feb-20 10:46 PM Do put effort into obtaining even illumination optically, as compensating via per-pixel modulation will introduce artifacts due to the mirrors slewing light while translating from on/off positions. Weak error but error nonetheless. 13-Feb-20 10:46 PM Any idea what exact DMD chip you have? You can delve further/optimize and compensate for pixel gap introducing diffraction artifacts. Even further you can compensate for the non-square pixel shape due to the mirror/pixel tilt angle. 14-Feb-20 07:59 PM @Metanoic I don't have a good idea yet, I am waiting to receive it as the listing for it did not describe it well. I thought it was collimated, but whenever I searched for stuff like that it looked like it was spreading light... Hrm. The DMD I don't have an exact model. Its crammed in there between stuff but the projector model is a Mitsubishi XD550U. 15-Feb-20 03:05 AM Hrmmmm so I think without the output lens that blows the image up to the size of a wall I can get about a half inch square of focused image... 15-Feb-20 03:05 AM which if I did my math right is just about 10um pixel size... 15-Feb-20 03:05 AM lol 15-Feb-20 03:05 AM So I may try some of my first runs of chips with no stepping and just that feature size as to not add any extra optics or complexity 15-Feb-20 03:17 AM https://media.discordapp.net/attachments/499873492477411339/678196078763311119/DSC_2965.JPG 15-Feb-20 03:17 AM https://media.discordapp.net/attachments/499873492477411339/678196108794527744/DSC_2964.JPG 15-Feb-20 03:17 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/DSC_2963-9C49F.jpg 15-Feb-20 03:17 AM itty 15-Feb-20 06:14 AM maskless litho? 15-Feb-20 06:14 AM how much did that projector run you? That’s been the next project I’ve been eyeing 15-Feb-20 06:18 AM Like 20 bucks a few months ago... Friend brought a bunch being decommissioned from a school working second hand. 15-Feb-20 06:18 AM And yea that's the goal 15-Feb-20 10:35 AM @idmb You can slice ruby yourself. I sliced ruby down to ~2mm thick, should be possible to get 1mm thick. Anything smaller will require polishing. 15-Feb-20 11:12 AM Aiming for 100um 15-Feb-20 09:15 PM <__ice9#6039> @ZeptoBars diamond saw? 16-Feb-20 03:34 PM I wonder how good diamond charged copper wire is.. which I know is used industrially in places 16-Feb-20 03:34 PM it is how some forms of ruby jewels for watchmaking are made.. through hole "olive" pattern 17-Feb-20 01:11 AM Hey @Mason_Yu, here's an interesting thing I found 17-Feb-20 01:11 AM https://item.taobao.com/item.htm?spm=a21wu.10013406.0.0.35fb71a66DCUDa&id=591694758984 17-Feb-20 01:11 AM Can you find out who actually makes these? 17-Feb-20 01:11 AM The projector itself is not that interesting, regular mems micromirror, but these seem to have a really tiny RGB laser module assembly, and since they're mems, it's going to be a collimated beam 17-Feb-20 03:13 AM @__ice9 Yes: https://www.youtube.com/watch?v=c3ifI7zqfL8 17-Feb-20 03:24 AM <__ice9#6039> Nice technique-- should be very clean 17-Feb-20 10:47 AM https://store.laserland.com/diode-laser-module/rgb-combined-white-laser-module.html 17-Feb-20 10:47 AM @Spirit It looks like this company makes a lot of RGB laser modules for projectors and laser light shows 17-Feb-20 10:47 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/O1CN01S4vmOi1HRpbgo5CJn_2569420755-2FCC0.png 17-Feb-20 10:47 AM This is one of the smallest modules they make. I can't find the exact module that was used in the mems projector 17-Feb-20 11:01 AM @Mason_Yu yeah these are huge 17-Feb-20 11:01 AM the mems one is TINY 17-Feb-20 11:01 AM the entire projector is the size of one of those drivers 17-Feb-20 11:02 AM So that particular mems projector was used in one personal robot company 17-Feb-20 11:02 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/O1CN01aG9Pk41TQhzOsPxiF_502377-BFC2E.png 17-Feb-20 11:02 AM That's a robot... I thought it was that mirror thing. 17-Feb-20 11:03 AM http://www.xiaobaojiqiren.com/about/ 17-Feb-20 11:03 AM That looks absolutely terrifying. 17-Feb-20 11:05 AM It seems to have recently gone bust. And people are trying to decode their projector board. Apparently you can't just feed it HDMI, it talks I2C and there's some custom protocol there 17-Feb-20 11:05 AM Well, I don't care about the hdmi part 17-Feb-20 11:05 AM I just want to slice the laser block off 17-Feb-20 11:17 AM Well I'm afraid it's one of those things where if I can't get an actual serial number on the module itself, I can never pinpoint who made it 17-Feb-20 11:17 AM I know these are used in small portable DLP laser projectors, but there's a lot of companies making them 17-Feb-20 11:17 AM Why do you want a tiny collimated RGB laser module? 17-Feb-20 11:20 AM To build a tiny RGB laser :P 17-Feb-20 11:20 AM I designed the world's smallest laser driver, so it's only natural that I try to make the world's smallest rgb laser pointer 17-Feb-20 11:20 AM Does it really make a difference if the thing is 6 cm long vs 2 cm long? 17-Feb-20 11:20 AM See above 17-Feb-20 11:20 AM And it's the "square-ey-ness" of it 17-Feb-20 11:20 AM Most pico projector modules are about as long as they are wide, so putting it into a small tube is problematic 17-Feb-20 11:21 AM Ah I see you've been hanging out in Styro's discord quite a bit 17-Feb-20 11:21 AM maybe 17-Feb-20 11:21 AM he paid for me to make the smallest laser driver 17-Feb-20 11:21 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200215_235244-66654.jpg 17-Feb-20 11:21 AM I posted the datasheet in #off-topic-thats-sometimes-on-topic 17-Feb-20 11:24 AM Okay, makes sense if you want to make the world's cheapest RGB laser pen. I'll try and request info from the seller. 17-Feb-20 11:24 AM not necessarily the world's cheapest 17-Feb-20 11:24 AM just smallest 17-Feb-20 11:24 AM I could probably make a cheap one myself, by building all the optical components, but it's a huge amount of work to get all the right optics and build an alignment jig to hold them in the right place while gluing 17-Feb-20 11:28 AM These tiny DLP projectors are not that expensive, ~$30 for just the board. They do ship overseas too 17-Feb-20 11:29 AM Yup, I just haven't found anything trustworthy 17-Feb-20 11:29 AM So might be worth it to get the board and tear it down yourself instead of trying to find the OEM info on the laser module 17-Feb-20 11:29 AM Yeah, that's what I'd do 17-Feb-20 11:29 AM Just have to get the right projector 17-Feb-20 11:29 AM Some are like this: 17-Feb-20 11:29 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/s-l500-877DB.png 17-Feb-20 11:29 AM You can see how big that is 17-Feb-20 11:29 AM (and an OPSL green laser!) 17-Feb-20 11:29 AM But there's also this kind 17-Feb-20 11:29 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/YKG_3f6mPqoH3yBpDAb2otSXtb8NJiu4-4CnGH9BMw-F15E7.png 17-Feb-20 11:29 AM The laser module is that seam under the pink sticker 17-Feb-20 11:29 AM This one is ultimems, I contacted them but no response so far 17-Feb-20 11:31 AM itty 17-Feb-20 11:31 AM very 17-Feb-20 11:31 AM Oh wow ultimems makes the absolute tiniest RGB laser modules 17-Feb-20 11:32 AM I know right 17-Feb-20 11:32 AM That's what you want in a pen 17-Feb-20 11:32 AM The one in the picture is marketed by other companies, believe it or not, as a raspberry pi hat 17-Feb-20 11:32 AM And yeah, that's the one I want in a pen 17-Feb-20 11:32 AM If I could get that, I'd be happy 17-Feb-20 11:32 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-0AA01.png 17-Feb-20 11:32 AM This is the bit I want 17-Feb-20 11:32 AM and you can see how compact that is, while still being collimated 17-Feb-20 11:32 AM imagine the amount of simultaneous alignment that goes into that 17-Feb-20 11:34 AM How does it steer? 17-Feb-20 11:34 AM Photoelectric something something? 17-Feb-20 11:34 AM Or voice coils? 17-Feb-20 11:34 AM MEMS micromirror 17-Feb-20 11:34 AM And that's tiny too 17-Feb-20 11:34 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/solution_canning_mirror_02-78C47.png 17-Feb-20 11:34 AM https://www.youtube.com/watch?v=UcT0ZIcL2B4 17-Feb-20 11:35 AM Ah, neat glad to know analog mems steering didn't die with the TI TALP dev kits 17-Feb-20 11:35 AM I have a sealed pack of TALP! 17-Feb-20 11:35 AM In non-array form anyway 17-Feb-20 11:35 AM Though TALP is mechanically mems, but electrically magnetic 17-Feb-20 11:35 AM So it's... micro... mechanical... mechanical systems. 17-Feb-20 11:36 AM I played with a TALP example once at this company I interned with 17-Feb-20 11:36 AM Mouse to laser pointer 17-Feb-20 11:36 AM I have just the bare, open-to-air modules on a ceramic substrate 17-Feb-20 11:36 AM two coils, two photosensors for closing the loop 17-Feb-20 11:36 AM and two teeny weeny magnets on the actual mirror 17-Feb-20 11:36 AM I think that's pretty much what that was, in a housing with the mouse interface via MCU 17-Feb-20 11:36 AM I drove it straight from my lab psu 17-Feb-20 11:36 AM super neat 17-Feb-20 11:36 AM never got around to making it actually work 17-Feb-20 11:36 AM but I think I have like 10 of them in a factory tray 17-Feb-20 11:37 AM Nice! 17-Feb-20 11:38 AM even accidently touched one and it didn't have any effect 17-Feb-20 11:38 AM don't think that would work with modern mems :P 17-Feb-20 11:41 AM I have a mems dmd that i got from electronics goldmine as unworking, for like $5 that I've been meaning to throw in the FIB and image 17-Feb-20 11:42 AM wow those are cool 17-Feb-20 05:14 PM Speaking of MEMS optics - I worked with this one back in the days: https://zeptobars.com/en/read/OPUS-Microsystems-OP-6111-2d-mems-laser-scanning-mirror 18-Feb-20 09:52 AM nice 18-Feb-20 11:49 AM anyone know an inexpensive source for bare/flying-lead alden connectors? specifically looking for the tube-side (male?) connector used on HeNe tubes 18-Feb-20 11:49 AM would rather not buy a nice melles griot supply and snip the leads on it, if i can help it 18-Feb-20 05:40 PM alternatively, if anyone has a HeNe laser tube with an alden connector that they could check for a model number, i'd super appreciate it 18-Feb-20 08:09 PM Successfully soldered my first circuit board with a SiPM sensor. Man that was tough. 18-Feb-20 08:20 PM Nothing like fragile leadless optical parts 18-Feb-20 08:27 PM First time soldering WLCSP package. It looks bad, but it works! 18-Feb-20 08:27 PM Picture? 18-Feb-20 08:27 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-34692.jpg 18-Feb-20 08:27 PM 1x1 mm SiPM surrounded by 0603 LEDs. 18-Feb-20 08:27 PM Too many photons getting from LEDs to sensor right now. 18-Feb-20 08:29 PM Yeah that's some tight packaging. Might have to do one myself soon too. Did you incorporate a transimpedance amp onto the board? 18-Feb-20 08:30 PM Surface tension of flux between LEDs and sensor made it twist, but it still works. 18-Feb-20 08:30 PM I’m using just a current sense resistor. 18-Feb-20 08:30 PM Not doing any sort of high speed stuff with it. 18-Feb-20 08:32 PM I'm interested in their high speed performance even with tiny signals. Why do you need 4 LEDs around it? One won't do? 18-Feb-20 08:36 PM It’s going to be for fluorescence measurement and in some situations the fluorescence is very weak and inefficient, so I wanted to maximize excitation light 18-Feb-20 08:36 PM Oh I see. On my design I just have an LED nearby to check if the thing is still alive lol 18-Feb-20 08:36 PM It will be in a pretty harsh environment and I want to have a consistent way to check that the amplifiers are still working 18-Feb-20 08:49 PM https://www.mouser.com/ProductDetail/ON-Semiconductor/MICROFC-30035-SMT-TR1?qs=sGAEpiMZZMtWNtIk7yMEsZQSjt2jgOZw0YLo1rX72qMplnV8BhmmgQ%3D%3D 18-Feb-20 08:49 PM Did you use this one? 18-Feb-20 08:59 PM No I used one from Ketek 19-Feb-20 03:46 AM <__ice9#6039> I wrapped the SMA905 fiber optic plug for my 800μm fiber jumper in PTFE tape, stuck it in an improvised ferrule made from 6mm PTFE tubing, and got it to fit into the apparently proprietary connector on my Mikron 78S IR pyrometer. When tested with a MAPP torch and a ceramic target, the result appeared to be the same as testing without a fiber connected. Successful from what I can tell. 19-Feb-20 03:46 AM <__ice9#6039> It's a dual-band NIR device, so it only cares about the ratio between intensity at the two wavelength ranges-- this normalizes for emissivity, but it turns out this is also equivalent to normalizing for aperture. 19-Feb-20 03:57 AM <__ice9#6039> The plan for the other end is to align the 3.175mm plug with a 3mm OD 1mm ID copper tube with a blackened interior several cm long to further narrow the aperture without contaminating the peripheral view with any significant NIR emission (estimated this should be viable below a tube temp of about 700K). Then that fits into a 3mm diameter hole in a graphite rod about 15cm long extending into the hot zone of the furnace. 19-Feb-20 03:57 AM <__ice9#6039> Heating by conduction and radiation along the tube from the hot zone should be under 80W 19-Feb-20 03:57 AM <__ice9#6039> The fiber should absorb less than 3W 19-Feb-20 11:19 AM @idmb still nothing just as a lat eupdate 19-Feb-20 11:19 AM lol 19-Feb-20 12:00 PM No attempts to align? Or no success? 19-Feb-20 04:53 PM No success yet 19-Feb-20 04:53 PM Some partial successes, but the machine still does not operate 19-Feb-20 04:53 PM Someone's in there close to every day 19-Feb-20 05:22 PM It shouldn't be that bad 19-Feb-20 05:37 PM It's not the same person day after day 19-Feb-20 06:13 PM That’s like trying to write code with a new person every line 21-Feb-20 08:44 AM I agree 21-Feb-20 11:03 AM answering my own question from earlier: HeNe lasers use Alden D-series connectors (D100 is the female/power supply side, D200 is the male/laser side) 21-Feb-20 11:03 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Screen_Shot_2020-02-21_at_11.02.11_AM-9E315.png 21-Feb-20 11:03 AM now to try and find a dead tube to rip a cable off of, or bite the bullet and pay $30 for a pigtail >.< 21-Feb-20 11:33 AM woot 21-Feb-20 12:17 PM https://images-ext-2.discordapp.net/external/HmBH-cCSFq7bdWDlntDMbxgu1lscO_EWtjQ2r2Ag_TM/https/pbs.twimg.com/media/ERPebbaWsAAxtrC.png%3Alarge 21-Feb-20 12:17 PM What a job title 21-Feb-20 11:27 PM https://www.gemsociety.org/article/table-refractive-index-double-refraction-gems/ Apparently rutile/anatase have extremely high indices of refraction. Are they widely used for optical components? 22-Feb-20 01:02 AM Rutile certainly gets used. 22-Feb-20 10:26 AM Hey hey guys, guess what club I joined? 22-Feb-20 10:26 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/DSC_2982-48030.JPG 22-Feb-20 10:26 AM Got this for free from the hackerspace here at the computer museum I am helping hack on some stuff this weekend. So yea nice little beginner HeNe laser kit ❤️ 22-Feb-20 10:26 AM very nice siemens lgr 7641 and power supply along with some cheap mirrors 22-Feb-20 11:04 AM Hmm, I've got a HeNe sitting in an old FTIR that doesn't have any real ideas planned for it 22-Feb-20 11:35 AM always handy to have one around. even more handy is having one fiber coupled.. I've been using the Kineflex assemblies for mine.. makes things much less cumbersome https://ebay.us/311ujq 22-Feb-20 11:37 AM laspr 22-Feb-20 11:37 AM lasor 24-Feb-20 03:42 PM ooh, was gonna ask if those fiber couplers work for HeNe but glossed over context 24-Feb-20 03:42 PM might have to grab one.. hmhmhm 24-Feb-20 03:42 PM having a nice big polarized HeNe is dangerous for my wallet.. :D 24-Feb-20 03:42 PM (now i need a nice small polarized/stabilizable one...) 24-Feb-20 05:23 PM Now idly wondering if it would be possible to replace every optical component in one of my old laser heads with uranium/thorium glass, including the fiber optics. I reckon that means it's time to make some of my researchers regret talking to me again. 24-Feb-20 05:29 PM for bonus-round trolling, you could propose replacing all the control electronics with ones based on uranium dioxide semiconductors 24-Feb-20 05:43 PM weird question, but.. anyone know of a thing like falstad's circuit simulator, but for throwing together optical experiments? i'm not even sure what to search for, or if this is even a simply-simulated thing 24-Feb-20 05:43 PM i'd like to build a two-mirror laser schlieren setup through an axis of my vacuum chamber and i sorta wanna spitball the layout of it, somehow 24-Feb-20 06:09 PM I like to be educational to my grad students. Sometimes that education is "Phil has terrible ideas." 24-Feb-20 06:39 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/DSC_2993-3B36A.JPG 24-Feb-20 06:39 PM It works :) 24-Feb-20 06:55 PM @qualia I use Optgeo for some stuff 24-Feb-20 06:55 PM It’s a nice way to see what misaligned lens systems do without doing math 24-Feb-20 07:41 PM @qualia it is within the realm of simulation, yes. Both via ray-tracing and more conventional maths. I can't vouch for any simple software UI/UX wise, but I do recommend both Zemax OpticStudio and COMSOL Multiphysics with the ray and/or wave optics modules. You can find both on the uhh... interwebs. Both have a steep learning curve but are very very useful tools. 24-Feb-20 07:49 PM zemax is the go-to for sure 24-Feb-20 07:49 PM COMSOL is what people use when they don't know what to use 24-Feb-20 07:49 PM it's so powerful 24-Feb-20 07:50 PM or they want to also model stuff like the thermal effects 24-Feb-20 07:50 PM Yeah it can do pretty much everything 24-Feb-20 07:50 PM Mots of the time it's way overkill though 24-Feb-20 07:51 PM yea it's a broadsword for sure, especially if you get the copy containing every module lol 24-Feb-20 07:51 PM it's like people using solidworks FEA rather than just calculating stresses really quickly 24-Feb-20 07:51 PM in those people's defense, following a YouTube tutorial is much easier than learning new-to-them maths 24-Feb-20 07:51 PM nevermind the paradox my statement introduces when someone views a maths tutorial on YouTube, lol 24-Feb-20 10:24 PM @Conmega congrats :D 24-Feb-20 10:24 PM envious of your extremely straightforward laser adventure, lol 24-Feb-20 10:24 PM I'll have to check out zemax. COMSOL's caught my eye for stuff like particle tracking or other weird coupled multiphysics stuff but it does seem like spooky intimidating overkill 24-Feb-20 10:24 PM i much prefer artificially constrained environments for working in narrowly-defined problem spaces over bewilderingly flexible does-everything-all-at-once tools; too easy to get lost & discouraged in the latter ime 24-Feb-20 10:27 PM Then optgeo is even simpler 24-Feb-20 10:28 PM oh cool 24-Feb-20 10:28 PM will probably poke that first then 25-Feb-20 03:19 AM I'll have to check that out too, there are Debian packages for it! 25-Feb-20 10:36 AM ogod there goes my productivity at work then 25-Feb-20 10:39 AM Interesting 25-Feb-20 11:53 AM @qualia heh thanks, though my laser was straight forward I don't know what I'll use it for yet. Time to do some reading on fun experiments I guess. 25-Feb-20 01:51 PM I got quotes back for ruby sheets... 1cmx1cmx0.5mm sheets for $100 each 25-Feb-20 01:51 PM I wish they were either thinner or cheaper 25-Feb-20 02:38 PM that seems reasonable for such a specialty item? 25-Feb-20 02:38 PM I mean if its a consumable for your project I guess yikes 25-Feb-20 02:46 PM it's not consumable but I want a stack of 20 of them 25-Feb-20 02:46 PM if they were same price for 0.1mm each I would go for it, but it's not clear whether 0.5mm will work 25-Feb-20 02:49 PM ah hrm 25-Feb-20 08:14 PM What do they promise other specs like doping level, 20/10 polishing? 25-Feb-20 08:16 PM Yeah 0.05% and good polishing 25-Feb-20 08:16 PM It’s “reasonably priced, but not exactly what I want” 25-Feb-20 08:16 PM I don’t get to just spend 2k, I have to go around and check if somewhere else can do much cheaper or much better 26-Feb-20 02:14 AM nice 26-Feb-20 03:59 PM got one of those electronic laser polarizers 26-Feb-20 03:59 PM excited to put it through its paces and see what mischief i can get up to with it 26-Feb-20 05:47 PM Anyone have recommendations for UV safety glasses? I'd like to have something on before I hook up a 50W UV led module :) I would assume "sunglasses" aren't the answer?? 26-Feb-20 05:47 PM I looked on amazon and started checking reviews only to re-affirm the knowledge that no smart people leave reviews... So they are pointless... 26-Feb-20 05:49 PM I've used these while working with UVC germicidal lamps and don't seem to be blind yet https://www.amazon.com/Uvex-S0360X-Ultra-spec-SCT-Orange-Anti-Fog/dp/B003OBZ64M/ 26-Feb-20 05:49 PM lol yeah the reviews are something else 26-Feb-20 05:50 PM oh yea I saw these 26-Feb-20 05:50 PM saw the "helped me sleep better" and was like ok yea nvm 26-Feb-20 05:50 PM (in fairness, they do help with that too) 26-Feb-20 05:50 PM but ok cool, I'll grab a pair, I mean I'll be working with UVA mostly I think but yea 26-Feb-20 05:50 PM also how? 26-Feb-20 05:50 PM I guess light blead through your eyelids?? 26-Feb-20 05:51 PM blue light does affect your circadian rhythm, it's the basis behind software like f.lux 26-Feb-20 05:51 PM oh right right ok 26-Feb-20 05:51 PM yea I saw the blue filtering, didn't put two and two with the whole sleep thing together 26-Feb-20 05:51 PM also why rooms with high-color-temperature light are 'energizing' and cooler/redder is more 'relaxing', subjectively speaking 26-Feb-20 05:51 PM probably why I can't sleep since I never tried the whole blue light filtering stuff 26-Feb-20 05:52 PM I thought that was debunked 26-Feb-20 05:52 PM it's almost a lost cause in this modern day and age because of how much artifical light we're constantly surrounded by. i notice it when i'm out camping for days+ at a time 26-Feb-20 05:52 PM has it? 26-Feb-20 05:52 PM no? its pretty common knowledge that blue light affects circadian rhythm I thought 26-Feb-20 05:52 PM but also the UV blocking affect of these is kinda... eh to me with these considering they sell "different colors" with the same claims?? 26-Feb-20 05:52 PM I mean I guess they could all block UV and just block different color spectrums too 26-Feb-20 05:52 PM but like... 26-Feb-20 05:52 PM ahh I see they are rated for different things, a question/answer reviews the models 26-Feb-20 05:52 PM Thanks I'll grab a pair :) 26-Feb-20 05:55 PM honeywell's uvex SCT (Spectrum Control Technology) glasses do have a noticeable effect on the transmission of certain wavelengths. i haven't tested it on the optical spectrometer but i can confirm that they optically block out everything above greenish 26-Feb-20 05:55 PM I have some UV cure stuff and the LED and driver now so I just need to bodge it into the projector and get that setup and see if I can get some litho stuff going 26-Feb-20 05:55 PM this is how i learned that streetlights actually have a somewhat nuanced color spectrum, likely for partially colorblind folks 26-Feb-20 05:55 PM sodium lamps are very cool 26-Feb-20 05:55 PM you can use them at very low T&P to make spectroscopic lines, or heat it up not too much and you get quite white light 26-Feb-20 05:58 PM low pressure sodium's one of the only monochromatic incoherent light sources, isn't it? always thought that was cool 26-Feb-20 05:58 PM San Jose replaced all the streetlights downtown with them, so a nearby observatory can notch filter them out, or so i'm told 26-Feb-20 05:58 PM very interesting zero-CRI light 26-Feb-20 05:58 PM @Conmega what wavelength is your cure light? 26-Feb-20 06:08 PM My province is planning to replace the sodium lights with LEDs 26-Feb-20 06:08 PM And nah sodium isn’t, just look up spectral calibration lamps 26-Feb-20 06:08 PM There are tons 26-Feb-20 06:12 PM oh you said UVA ok nvm 26-Feb-20 06:12 PM and, interesting 26-Feb-20 06:17 PM yea its basically almost violet I think? 26-Feb-20 06:17 PM high NM 26-Feb-20 06:17 PM so not super exciting 26-Feb-20 06:17 PM but I do have a UVA/UVB thing downstairs I think? 26-Feb-20 06:17 PM Maybe some UVC? 26-Feb-20 06:17 PM 100W mercury vapor cure station 26-Feb-20 07:14 PM @qualia indeed sodium lamps are easily filtered to reduce their light polluting effects for astronomy/astrophotography. That is one of the issues with the new LED street lamps. 26-Feb-20 08:15 PM Only bad high pressure sodium lamps 26-Feb-20 08:15 PM The hot ones are very broad... 26-Feb-20 09:18 PM in general, street/outdoor applications of sodium lighting are low pressure - nice and narrow band easily filtered 26-Feb-20 09:20 PM Looks like street and highway lights are different ! 26-Feb-20 09:20 PM Highways have high pressure broad bright ones 26-Feb-20 09:20 PM Typically 26-Feb-20 09:31 PM depends on the municipality, typically you would only see low pressure sodium (yellow/orange) or mercury vapor (bluish).. now days you're liable to see all sorts. Broader band allows for easier color determination with our eyes, so it would make sense for highways to use them if you are concerned about being able to identify a vehicle by color (e.g. highway patrol) 26-Feb-20 09:52 PM The joy of San Jose is that it's had sodium lighting since very, very early on because of Lick Observatory. The city was very proud of Lick and happy to accommodate them. In the pre-Google maps era when reading physical maps, this was a bit of a problem as there's some things you just can't read at night. Like the pink marked cultural sites, such as the San Jose Symphony. 26-Feb-20 10:21 PM That is what I would call a fun fact 26-Feb-20 10:37 PM I REALLY, REALLY WANTED TO GO TO THE SYMPHONY THAT NIGHT IN HIGH SCHOOL BUT COULDN'T FIND IT [takes deep breath] I'm fine really. Everything is fine. 28-Feb-20 01:16 AM need to pimp osa for 100 MHzish res 28-Feb-20 10:41 AM @Mezmorizor that’s a fun system you described in your intro. 28-Feb-20 10:42 AM @Mezmorizor I feel like I've met your PI 28-Feb-20 10:43 AM You probably have tbh. The cation stuff is new/not up and running, but the field is small enough that describing what I do is a bit of a doxx 28-Feb-20 10:43 AM And thanks, I agree that it's pretty neat. It's kind of crazy how not hard getting to sub Kelvin temperatures is 28-Feb-20 10:44 AM Well you can do that even without the droplets 28-Feb-20 10:44 AM tiny hole + big pressure gradient = where did all my QM states go? 28-Feb-20 10:47 AM True, but that's also kind of what I mean. It feels like it should be harder than it is 28-Feb-20 12:20 PM also @funranium looks like the Neumark group has a droplet machine if you want to see one in person 28-Feb-20 12:20 PM or rather, hear one. 28-Feb-20 02:30 PM Oh, I have beheld the majesty. 28-Feb-20 04:06 PM Spoilers for those that don't know, it sounds like a helium compressor and a lot of vacuum pumps :p 28-Feb-20 04:06 PM And cation, not action. Mobile is stupid like that. 28-Feb-20 04:06 PM And laser sounds 29-Feb-20 01:39 AM https://twitter.com/styropyro_/status/1233575015049781249 I'm just posting this to annoy @funranium 29-Feb-20 01:40 AM but it's a nice pic 29-Feb-20 04:36 AM herrow 29-Feb-20 08:29 AM What exactly were you hoping to do with the Iodine stabilized HeNe? HeNe output is already pretty good with nothing special in particular, if I'm not being dumb, a single mode operation alone should give you ~1.6 GHz jitter. At that level you already need a pretty non trivial interferometer to even notice the jitter. 29-Feb-20 08:29 AM That said, while I don't personally have experience doing it, there's a lot of literature about this in the ~60s in optics journals you should be able to find with a google scholar/scihub combo 29-Feb-20 08:29 AM And there's also this 29-Feb-20 08:29 AM https://www.repairfaq.org/sam/laserhsl.htm 29-Feb-20 08:29 AM https://www.repairfaq.org/sam/laserhen.htm#hentoc 29-Feb-20 08:54 AM yeah I know sam's laser faq 29-Feb-20 08:54 AM and yes I want to use it as a reference 29-Feb-20 08:54 AM I have a beat note stabilized HeNe - but it would be also nice to I2 stabilize it and make it a good (known) reference 29-Feb-20 08:54 AM @Mezmorizor 29-Feb-20 08:54 AM for spectroscopy applications etc (as the reference for the spectrometers) 29-Feb-20 08:54 AM I mean of course I could try to use another laser that I stabilize against a proper vapour cell 29-Feb-20 08:54 AM but HeNe is the most common Lab standard for spectroscopy - there might be reasons 29-Feb-20 09:37 AM Sigh. Thank you @GigaSquirrel. I needed my Two Minutes Hate. 29-Feb-20 09:37 AM Always happy to help ❤️ 29-Feb-20 10:05 AM He’s in the wrong state to be a laser cowboy 29-Feb-20 10:36 AM Speaking as a private pilot, I’m glad I’ve never been blinded by lasers, but I have been shot at with fireworks. 29-Feb-20 10:36 AM Some idiot was shooting aerial shells right at the approach end of the runway. 29-Feb-20 10:36 AM Both myself and the business jet landing ahead of me experienced flak. That’s not something I’d ever figured I’d have to worry about as a private pilot. Yes, it was July 4, but you’d think maybe the person doing it would realize that of all the places to shoot off fireworks, doing it on the final approach of an active runway would be more likely to attract law enforcement? 29-Feb-20 12:01 PM HeNe is a good choice for that kind of work, probably the best. I'm more saying make sure you're not spending a ton of time making something that isn't even your resolution limiter better because HeNe's are already quite good there out of the box. That said, I know relatively little about HeNe's, they're kind of just the thing I use to align our high power lasers 29-Feb-20 04:48 PM does anyone know if cd-rom read heads suspension/corrector [coils] have some sort of positional feedback (distance/displacement sensor) ? 29-Feb-20 04:51 PM No, the feedback comes from the way the laser comes back and gets picked up. I believe Sam Zeloof has a great video explaining this for a blueray player head which is a similar principle. I am sure there are tons of other videos too. So without the laser there is no feedback 29-Feb-20 04:51 PM oh, will try to dig for his 29-Feb-20 04:51 PM the end goal is a rotary encoder (magnetic?) for metrology/machining that can do more than just quadrature of an encoder disc 29-Feb-20 04:51 PM and somewhat basing the idea off an old Leitz optical dividing head 29-Feb-20 04:51 PM and pivoting a prism to adjust the focus path +/- 15 arc mins 29-Feb-20 04:51 PM (the glass disc scale has marks every 15') 29-Feb-20 04:51 PM the end adjustment/reading is down to 2 arc seconds, easily splitable to inbetween for arc second resolution 29-Feb-20 04:51 PM also, I dont see in titles anything regarding bluray or cd, etc on his YT channel 29-Feb-20 04:51 PM maybe on some other medium 29-Feb-20 07:31 PM I worked on refurbishing a mill with analog optical encoders. 29-Feb-20 07:31 PM They had a pair of lamps and photocells 29-Feb-20 07:31 PM Generated a pair of out of phase sine waves. You can read them like quadrature and also interpolate. 29-Feb-20 07:31 PM Another used analog resolvers 29-Feb-20 07:43 PM the one I am looking at is more like a microscope on the scales 29-Feb-20 07:43 PM and yeah, I guess a resolver is what I am imagining to some degree 01-Mar-20 04:23 AM @Mezmorizor my interferometers have like <100MHz resolution 01-Mar-20 04:23 AM btw do you guys also fiddling around with (low noise) laser diode current sources? I mean building some and the associated stable reference voltage sources for the controlling loop? 01-Mar-20 11:31 AM Out of curiosity, what's your set up here? Sounds like you should go for it though, that interferometer is good enough to tell the difference 01-Mar-20 07:56 PM @Noxz it may be on Sam's (not zeloof) laser faq, diyoupcb also has some really good blog posts about it 01-Mar-20 09:29 PM ah, nice thanks 01-Mar-20 09:41 PM I'd like to think that someone would have hack a cdrom image for position, and aim a reader at it.. but maybe it requires spinning? 01-Mar-20 09:41 PM Inspired on a sunny day, we though we would install sunglasses on the pickup and filter out the excess of light. ... super neat 02-Mar-20 01:07 AM @Noxz cdrom tracking is the search you want to do, get results like this and more detailed too http://hyperphysics.phy-astr.gsu.edu/hbase/Audio/cdplay3.html 02-Mar-20 01:07 AM About Midway down this is what i was thinking of earlier, but i guess it doesn't have that much control system theory, i must have researched that separately around the time i first found this 02-Mar-20 01:07 AM http://www.diyouware.com/node/161 02-Mar-20 08:34 AM https://www.youtube.com/watch?v=tozuzV5YZ7U 02-Mar-20 08:34 AM haaax 02-Mar-20 03:39 PM Looking more and more into using bluray/whatever laser to scribe a rotary scale for use as a rotary encoder inside a rotary table/dividing head for machinery.. What material is lased and what is the read head is still a concern 02-Mar-20 03:39 PM I like the idea of giving it a standard pulsed freq based on RPM 02-Mar-20 03:39 PM To create 02-Mar-20 04:15 PM That phr-803t head could be used to read and writr 02-Mar-20 04:15 PM Just use a different color that's less etchy, and/or lower power 02-Mar-20 04:15 PM I've got one of the diyoupcb controllers they released, not sure they're still available for purchase, but i think they released the circuit boards and BOM 02-Mar-20 04:15 PM They had all the controls and feedback outputs broken out to pins and even some servo circuitry available, I think 02-Mar-20 04:15 PM (broken out and amplified/buffered, as I recall) 02-Mar-20 04:15 PM You can download the Eagle's CAD files and the BOM from here: TwinTeethPickupDriverV3.3.zip 02-Mar-20 04:15 PM http://www.diyouware.com/downloads/TwinTeethPickupDriverV3.3.zip 02-Mar-20 04:15 PM Might send them an email to see if they have any of the controllers/drivers still available... Since it was a component of their overall system, they might have some stock of them and not of the rest of the mechanical parts to sell whole systems 02-Mar-20 05:44 PM yeah, would make things much easier 02-Mar-20 05:44 PM so the idea is to somehow mark or expose (photoresist?) some optical glass (mainly as many of them have really low CoTE, and thus geometrically stable) , likely as radial lines, to then be picked up by a relatively normal optical detector tha tis susepnded and coils able to move it slightly - with a displacement sensor, to obtain greater resoltuion.. ie, if marks every 15 arc mins, and the read head is able to swivel +/- 15 mins, then displacement of that, plus the count of ticks that has gone by, would equate the final rotation 02-Mar-20 05:44 PM the main thing would be consistent (over-written a few times for "elastic averaging") pattern, high contrast, and easily read when manually rotated (non-disc spinning, but suuper slow) 02-Mar-20 05:44 PM radial would be accomplished by simply moving the focusinglense with positioning mechanics while keeping the same frequency/data, with same width lines (not tapered) 02-Mar-20 06:02 PM Ah, this video. It is a fine display of the very different risk models that America operates under compared to Europe and Russia. America is deterministic with defined "Nope, cannot go here, laser shuts off if people enter the space." The European model is probabilistic with "How likely is it someone would go into a space and get injured? And, really, it kinda the victim's fault, right?" This is also kinda related to how personal liability tort law works on the other side of the pond. 02-Mar-20 07:34 PM @Noxz how would you so precisely rotate the glass to perform the etching? Seems like you'd need to have a system that has better error rotationally than what you want to use it for 02-Mar-20 08:08 PM that's part of the reason for 'elastic averaging' 02-Mar-20 08:08 PM also, the only precision of the process is the speed of the spinning disc (rpm) and the frequency of the diode 02-Mar-20 08:08 PM so long as speed is maintained well (flywheel?) then the output pattern should be decent 02-Mar-20 08:08 PM also, this is why I am chatting about it here, to try and figure if it is feasable, etc 02-Mar-20 08:08 PM logical topics I am missing 03-Mar-20 07:24 AM hey so, laser safety q (cc @funranium ) -- i got some snazzy HeNe laser alignment glasses a bit ago and they have a substantial gap between my cheek and the bottom of the frame, to the point that i could theoretically end up shooting a reflection up along my nose and into my eye (albeit at a very acute angle) 03-Mar-20 07:24 AM are these glasses crap? are all wraparound plastic glasses affected by fit problems like this? can i bodge a light guard together with gaffer's tape? is this not really that big of a concern with a <20mW HeNe laser? 03-Mar-20 07:31 AM Regarding optical disk tracking - I've photographed DVD sensor, which tracks focus via astigmatic focusing and track position: https://zeptobars.com/en/read/DVD-photosensor-quad-photodiode-astigmatic-focusing 03-Mar-20 09:36 AM Very nice 03-Mar-20 09:36 AM Tracking isn't really what I am going for.. Just want to expose a pattern (via photoresist? Or carbourizing?) onto optical glass as a rotary scale/encoder, so the idea of reading radial lines more than data bits (and thus no rows) I think would work better 03-Mar-20 09:36 AM Awesome shot though 03-Mar-20 09:36 AM Maybe tracking of the radial lines could work... 03-Mar-20 10:51 AM The challenge of laser safety eyewear isn’t just filtration, but fit. If they’re uncomfortable or have significant gaps due to face shape, then people won’t wear them. It’s also the reason some labs insist on the fully enclosed goggle style rather than eyeglasses. For your second question, at 20mW your main concern is intrabeam exposure or specular reflection. Scatter at that power isn’t and issue. 03-Mar-20 10:53 AM @funranium have you seen anything / been involved in anything related to using cameras + goggles with a screen (like VR) for laser safety? 03-Mar-20 10:53 AM It seems like soon enough that will be viable without being too disorienting in terms of field of view / latency 03-Mar-20 10:57 AM Absolutely have. And yes it is disorienting. I am very fond of the camera-display screen wavelength shift of just using cheap cameras for monitoring and proper high OD goggles. You are protected but can still see your beam on the screen with your gogs on. This is a stupid trick I did with a Class 4 532nm system and my phone. Blew the mind of the CEO demonstrating his PIV laser system. It also removed his not wearing gogs excuse of “I need to see the beam to align”. 03-Mar-20 10:57 AM That, incidentally, is a BS excuse because your colleagues align invisible wavelengths all the time and seem to do just fine. 03-Mar-20 11:08 AM I aligned my whole pulse shaper using the 80MHz fs oscillator with an ND2 filter, and a raspberry pi IR camera streaming to a tablet with a nice colourmap 03-Mar-20 11:08 AM Even without the nd2 you couldn’t see the beam by eye 03-Mar-20 11:09 AM That said, the VR disorientation does go away if you do it long enough. Your proprioception shifts and you don’t whack your hands into things anymore. Watching telemedicine people get comfortable with it is amazing with the speed they adapt. 03-Mar-20 11:10 AM Uh, that’s different ? 03-Mar-20 11:10 AM In telemedicine aren’t the cameras fixed / moving slowly? 03-Mar-20 11:10 AM Compared to being attached to your head and moving rapidly all over the place? 03-Mar-20 11:10 AM FPV drone pilots manage of course 03-Mar-20 11:10 AM Is there any video goggle system you know of ready to go for IR? 03-Mar-20 11:10 AM Yeah all the telemedecine I see is either a fixed camera, or the camera is just on the side of someone's head filming it FPV and then monitored on a regular screen remotely for consultation / advice 03-Mar-20 11:59 AM I don’t. 03-Mar-20 12:08 PM vive pro + head-mounted multispectral cameras sounds like an exquisite(ly expensive) project 03-Mar-20 12:17 PM I mean the good laser goggles cost 2x what a vive does 03-Mar-20 12:17 PM oh haha the vive pro is more than I thought 03-Mar-20 12:24 PM https://twitter.com/ToughSf/status/1234887007333052416 03-Mar-20 12:25 PM bit of a jump from 7W output power to 'pulsed laser rocket launch' 03-Mar-20 12:29 PM Oh yes. 03-Mar-20 12:29 PM But still a very decent efficiency. From what I understand anyway. 03-Mar-20 12:32 PM tbh that account likes to vastly exaggerate what can be done with the tech they're presenting... 03-Mar-20 12:33 PM the paper's interesting nonetheless 03-Mar-20 12:34 PM oh I'm not doubting that the tech is interesting, only that everything they post is the solution to fusion, spacetravel and whatnot 03-Mar-20 12:35 PM gotta get those social media impressions 03-Mar-20 12:35 PM low-cost tunable femtosecond light sources.. the unwashed masses don't know what they're missing out on 03-Mar-20 01:53 PM Heh. I see a very familiar follower tearing them a new one over efficiency and wishful thinking. 03-Mar-20 02:03 PM thank goodness 04-Mar-20 01:31 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-4D36F.png 04-Mar-20 01:31 PM going to attempt to make a random laser with this 0.9mm slice of ruby I made 04-Mar-20 01:38 PM @LRM Since this is actually more optics-based: Typically in a ruby laser the ends of the rod form the cavity and it's crucial they're parallel. Here the ruby will actually be within an a cavity with a flat mirror and a refocusing mirror. Like here: https://www.osapublishing.org/osac/abstract.cfm?URI=osac-2-1-184 except pumped with a 400nm 10ps beam. 04-Mar-20 01:38 PM Flatness and parallelness still matter, but nowhere near as much 04-Mar-20 01:43 PM ahhh i was wondering how you were getting around the need for parallel faces, makes sense now 04-Mar-20 01:44 PM parallel polished faces with an anti-reflective coating would be really nice 04-Mar-20 01:44 PM my output coupling is closer to 2.5% than their 1.8%, which is the right direction for a lossier system... So, we'll see 04-Mar-20 01:45 PM when i was picking up an eBay purchase I actually was at a really nice optical shop recently 04-Mar-20 01:45 PM he was showing me a big 8" optical flat he had as an extra from some custom job... 04-Mar-20 01:45 PM lucky you are working at much smaller scales 04-Mar-20 02:43 PM anyone building a CO2 laser? 04-Mar-20 02:43 PM I know someone was doing a fair bit of work making / designing one. 04-Mar-20 02:45 PM https://gizmodo.com/talk-a-load-of-exhaled-hot-air-into-this-laser-5597232 04-Mar-20 03:20 PM i know that's cooling water but the droplets just make me think of spit condensation 04-Mar-20 03:20 PM also Saliva Excimer would be an incredible band name 04-Mar-20 03:52 PM Today, I had to seriously tell a grad student that, no, that pair of Oakleys are not laser safety eyewear for his 15W 532nm system. Yes, they are wraparounds but that really isn’t the point. 04-Mar-20 03:52 PM shakes head in despair 04-Mar-20 04:52 PM if questioned is "I know, it's not meant to be for safety. I just get headaches from the bright light." a suitable response? 04-Mar-20 04:52 PM "I don't want a seizure from this 5Hz monster" 04-Mar-20 07:03 PM @idmb how did you make the ruby? 04-Mar-20 07:05 PM Oh I didn’t make the ruby sorry 04-Mar-20 07:05 PM I made the slice by cutting it off 04-Mar-20 07:07 PM sweet 04-Mar-20 07:07 PM looks pretty, how'd you cut it? 04-Mar-20 07:07 PM Diamond saw 04-Mar-20 07:07 PM Usually used for cutting mirrors 04-Mar-20 07:08 PM @samy https://www.youtube.com/watch?v=znuiIAiN8uM 04-Mar-20 07:08 PM here are some bad ideas 04-Mar-20 07:12 PM haha 04-Mar-20 08:51 PM No, @idmb, that is not a satisfactory response. It might work with a particularly dim OSHA inspector, however. 04-Mar-20 08:53 PM These trick questions are key for inspecting inspectors 04-Mar-20 08:56 PM This is why my researchers are annoyed/pleased with me. I am much more knowledgeable/irritating than actual inspectors, but actually helpful. 04-Mar-20 08:56 PM On sorry to burst the bubble of the exhale laser guy but that discharge color looks exactly like plain ole air discharge. 04-Mar-20 08:56 PM Air and water vapor 04-Mar-20 09:12 PM Which is unsurprising because exhaled breath is only ~4% CO2. That's a lot more than normal air, but it's still ~75% N2 05-Mar-20 06:26 AM what are known common films that I can 'burn' (making patterns on glass) with UV, ie, 'carbouriziing' .. and at decent resolution - which I woul think is easily obtainable 05-Mar-20 08:54 AM http://laserstars.org/history/mars.html 05-Mar-20 08:54 AM o3o 05-Mar-20 09:41 AM not quite right, I don't think 05-Mar-20 09:41 AM it's ASE but without a cavity it's not coherent & has no gain clamping 05-Mar-20 06:16 PM looks like MoO3 is used as a chemical assist for laser engraving - trying to find more info on that than just a MSDS 05-Mar-20 06:16 PM ah, a patent.. US9498999B2 05-Mar-20 06:28 PM question is.. can a UV disc laser convert it? 05-Mar-20 09:12 PM Isn't that for like, etching metal? 05-Mar-20 09:12 PM Or at least changing the color... 05-Mar-20 09:18 PM What I want to do is basically like PR on some optical glass to use as reading marks (optical.. but I suppose some sort of magnetic version could do, but then still theidea of getting it on and exposed properly).. so I figure simply lasing some material on the glass that will basically bake on, like enamel - or laser engraving should work.. but the glass istself wont be mcuh affected by a simple UV laser 05-Mar-20 09:18 PM just thinking of the various ways to write onto the medium I want 05-Mar-20 10:13 PM Why not just use photoresist, a 405nm laser, and then HF (whink rust remover, or glass etchant) 05-Mar-20 10:13 PM Photoresist from china on ebay works with 405nm and is super cheap 05-Mar-20 10:13 PM Idk what resolution you're after, and coating a non-flat sirface like evenly could be challenging or unattainable 05-Mar-20 10:13 PM (but if your feature size is big enough, that might not matter much) 05-Mar-20 10:29 PM right, so all that is certainly an option too.. I guess I was simply pondering the idea of lasing the glass directly (or a chemical on the glass.. which I mentioned photoresist as a possible option) 05-Mar-20 10:29 PM I think photolithography methods for etching a layer ontop of the glass is going to be a better bet, but still all just idea forming right now 06-Mar-20 05:20 PM Just make sure your aren't illegally importing controlled materials with the photoresist and that you store it right. Some of them are rather nasty and prone to spontaneously combusting. 06-Mar-20 08:58 PM Unfortunately they don't say what the photoresist is... 06-Mar-20 09:06 PM Use NMP if you want to remove photoresist 06-Mar-20 09:06 PM That actually I will be trying soon to remove kapton 06-Mar-20 09:31 PM I've got a gallon of NMP of you want a 100ml or so 06-Mar-20 09:31 PM And it isn't magic for removing photoresist... At least hasn't been so far. Been soaking my electroform for 2 days now in cold NMP.... hopefully it turns out better than the hour or so in hot NMP I tried before 07-Mar-20 09:56 AM NMP can also suspend graphene sheets 09-Mar-20 05:42 PM i wonder what kinds of delightful liabilities i would open myself up to if i just threw up a pile of 3D-printable HV alden connectors on github 09-Mar-20 05:42 PM i bet not a single one of these things would pass hipot testing https://twitter.com/profanegeometry/status/1237173062593679361 09-Mar-20 05:50 PM can't be that bad 09-Mar-20 05:50 PM shaving the casing off wire and just shoving it into a socket with a cable tie and elastic holding it there is not that unheard of 09-Mar-20 05:50 PM Speaking of high voltage and optics though 09-Mar-20 05:50 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-B30DD.jpg 09-Mar-20 05:50 PM alligator clips + a plastic tent to inhibit accidental touching sound good to you guys? -_- 09-Mar-20 05:50 PM Pockels cell 09-Mar-20 05:53 PM yeah, these are replacing two bits of that same gray 15kV wire i'd folded over thrice and mashed into the socket, which.. may or may not have been the cause of this 30kV supply maxing out at half that. or it could've been that one of the driver boards' secondary output was unseated. who knows 09-Mar-20 05:53 PM oh fun 09-Mar-20 05:55 PM That passes muster by me @idmb. It shows effort and considered thought that not all physicists do. It perhaps shows that, like me, you would prefer to not get shocked again. 09-Mar-20 05:56 PM hehe 09-Mar-20 05:56 PM it also helps that the high voltage is only there for a few ns every ms 09-Mar-20 05:56 PM I guess 09-Mar-20 05:56 PM maybe us 09-Mar-20 05:56 PM How does that affect what high voltage "feels" like? 09-Mar-20 05:57 PM the skin effect is a (sometimes life)saving grace, though not ideal to be relied on 09-Mar-20 05:57 PM a fun RC circuit 09-Mar-20 05:57 PM As far as liabilites, @qualia, you would kinda kinda count as a manufacturer, though it depends on whose definitions you're reading at the moment if you're an OEM or product manufacturer. 09-Mar-20 05:59 PM i have an old paper on electrical injuries and the pulsed nature of e.g. capacitor banks seemingly makes them vaguely more forgiving than, say, a continuous arc-flash energy hazard breaker panel or somesuch 09-Mar-20 05:59 PM it's very different from a capacitor bank too 09-Mar-20 05:59 PM tiny current 09-Mar-20 06:00 PM iirc pockels cells are <10kV and deliver a couple amps of current, every firing? 09-Mar-20 06:00 PM oh hm 09-Mar-20 06:00 PM maybe i'm thinking of kerr cells 09-Mar-20 06:00 PM https://ekspla.com/product/high-voltage-power-supply-ps4012-for-pockels-cell-drivers/ 09-Mar-20 06:00 PM 5W 4kV to 150W 4.4kV 09-Mar-20 06:08 PM also a pulsed power system becomes markedly more electrically dangerous as the rep rate increases, and the charging supply may end up being a bigger concern than the bank its charging.. naively, 150W @ 4.4kV is a power supply capable of putting out 34mA at that voltage. bridging that across the heart could quite certainly prove fatal, but a brush with a single limb may just be a moderate to severe localized burn, barring some other path to ground (the table itself?) 09-Mar-20 06:13 PM Just received a brand new galvanometer with an f-theta lens today 09-Mar-20 06:13 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/JPEG_20200309_210042-DD954.png 09-Mar-20 06:13 PM Now I need to struggle with its driver and software... 09-Mar-20 06:14 PM https://www.researchgate.net/publication/323058912_A_Complete_Electrical_Shock_Hazard_Classification_System_and_Its_Application here's a fun read on shock hazard quantification -- not as old of a read as i thought, actually. 2018 vintage 09-Mar-20 06:50 PM FUN FACT: The early research that lead to the design of GFCIs was thanks to a fun Stanford study where a professor had students hold on to electrodes and slowly cranked up the voltage and current to see when they cried out, dropped the electrode, fell out of the chair, or were unable to let go. 09-Mar-20 07:01 PM yay class participation :D 09-Mar-20 07:23 PM There is picture of the professor smiling, smoking his pipe, as the there is a grad student grimacing in pain as he doubles over. 09-Mar-20 07:39 PM That sounds unrelated to the experiment and more to do with coursework 09-Mar-20 07:46 PM <𝓕ermion#6024> buy or no buy? 09-Mar-20 07:46 PM <𝓕ermion#6024> Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/89731655_2475522389214447_6864155438988918-240D3.png 09-Mar-20 07:54 PM I wouldn’t, but then I would also be going down to break this further rather than cutting a power cord. The power supply may be fine but I wouldn’t count on anything else. 09-Mar-20 07:54 PM Also, I hope you have the requisite power at home. 09-Mar-20 07:55 PM You should expect for basically every optic to be burnt 09-Mar-20 08:32 PM The good news is that the OC and HR on these are fairly easy to replace. Easy enough I'd trust freshmen to do it. You'll be in trouble if the brazed windows on the tube are shot, in which case you have a lot of salvageable parts...and some beryllium waste to get rid of for the ceramic sheath on the tube. 09-Mar-20 08:36 PM Is the inside of those basically the same set up as the quanta rays? If so, yeah, replacing those isn't really any harder than doing the initial alignment you'd need to do anyway. 09-Mar-20 08:37 PM Simpler, really. 09-Mar-20 08:37 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/37828_9_-EF8CB.png 09-Mar-20 08:37 PM Yeah powering it is going to be a real challenge 09-Mar-20 08:37 PM So is cooling it 09-Mar-20 08:37 PM Couldn't believe my eyes at first, but yep, 60 kW 09-Mar-20 08:37 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/37828_5_-F8B1A.png 09-Mar-20 08:44 PM 5 GPM 09-Mar-20 08:44 PM Holy 09-Mar-20 08:45 PM Cooling shouldn't be a big deal. Power though... 09-Mar-20 08:45 PM It basically needs a sink running at full blast to cool it 09-Mar-20 08:45 PM ^ 09-Mar-20 08:49 PM Uhh, a 5 GPM faucet? 09-Mar-20 08:50 PM We measured ours to be around 22 L/min 09-Mar-20 08:51 PM Oh, but it's not a home faucet is it? 09-Mar-20 08:51 PM I calculated that my bathroom faucet was barely going to be able to cool my laser, flow rate just too low 09-Mar-20 08:51 PM And pressure requirement needs to be taken into account as well 09-Mar-20 08:52 PM Flow rates are also for the upper temp range typically 09-Mar-20 08:52 PM Cold city water is pretty low 09-Mar-20 08:53 PM Even if your indoor faucets don't work, most outdoor faucets go well over ~10 GPM 09-Mar-20 08:53 PM And if you're seriously considering a laser like that I assume you're not in an apartment 09-Mar-20 08:53 PM Which might be a bad assumption admittingly 09-Mar-20 08:53 PM Why does anyone need these high power argon ion lasers anyway? 09-Mar-20 08:54 PM Large amount of ice and a circulating pump? 09-Mar-20 08:56 PM Bingo, that's probably what I'm going to do. With a radiator in front of copper tubes in ice bath and a high pressure well pump 09-Mar-20 08:56 PM For the short term anyway. 11-Mar-20 09:27 AM Anyone know what I could use to safely clean a KTP doubling crystal that wont also hurt the AR coating? There's some sort of gunk on the front face and I'm a bit scared to just acetone it 11-Mar-20 09:27 AM Hard to see due to bad camera, but it's very noticeable in person 11-Mar-20 09:27 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20200311_122130-545A7.jpg 11-Mar-20 09:39 AM Isn’t methanol a little gentler? You’re the chemist, I’ve just been told “acetone for cheap stuff, but always methanol if the coating is important.” 11-Mar-20 09:50 AM I have no idea what those coatings are made of, and it looks like the smudge is the epoxy holding the thing down there too which makes it harder 11-Mar-20 09:50 AM I guess I'll see if I can get a hold of the supplier 11-Mar-20 09:50 AM And by harder I mean methanol tends to not do much to polymers 11-Mar-20 10:13 AM Seconding @idmb laser folk wisdom. Also spring for the nice folded up lens tissue in your hemostat. 11-Mar-20 10:21 AM Newport says use DI water if you don't know: https://www.newport.com/n/how-to-clean-optics 11-Mar-20 10:23 AM Speaking of which, anyone have ideas about cheaper sources of DI water for a hobbyist besides buying by the gallon from a drugstore. 11-Mar-20 10:40 AM your drugstore sells DI water? o.O 11-Mar-20 10:46 AM Rite Aid always has. You only make the mistake of not reading the labels when shopping for the camping trip at stupid in the morning once. 11-Mar-20 10:50 AM Uhh...hu? You can get DI water here in every Supermarket and Hardware store for like a buck or two for 5l 11-Mar-20 10:50 AM people use it everywhere for clothing irons, diluting cleaning agents and whatnot 11-Mar-20 10:51 AM You could get an RO/DI system for like $150 on ebay it looks like, but I'd honestly probably just keep buying the gallons if I were you 11-Mar-20 10:51 AM An 18.2 MOhm system is like ~$800 secondhand if you want to be very overkill 11-Mar-20 10:52 AM i've explicitly gone and looked for DI water for electrical insulation purposes and all i've ever found are Whole Foods' highly suspect by-the-jug dispenser things, never seen it for sale on the shelf as a pre-bottled thing 11-Mar-20 10:52 AM not 'distilled' but 'deionized' 11-Mar-20 10:52 AM i must be doing something wrong/completely blind 11-Mar-20 10:53 AM I mean, I usually assuming distilled and deionized are the same for most purposes (non-analytical chemistry) 11-Mar-20 10:54 AM yeah same 11-Mar-20 10:54 AM it's sold as distilled here, but I assumed it's just marketed as DI somewhere else 11-Mar-20 10:55 AM And I’m not doing trace element analysis so I don’t usually need insane purity 11-Mar-20 11:06 AM Distilled is probably good enough for most uses, but it's not the same thing 11-Mar-20 11:06 AM Though be a bit careful, you don't necessarily need to be doing insane analytical work to run into issues. My gen chem professor had to buy an expensive DI system because various reactions simply didn't work without it (eg copper sulfate-aluminum foil displacement reaction) 11-Mar-20 11:16 AM I enjoy colour filters 11-Mar-20 11:16 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/video0-B55AC.mov 11-Mar-20 11:50 AM gah https://twitter.com/profanegeometry/status/1237811825212665856 11-Mar-20 11:50 AM so frustrating. like a couple years back, supposedly, you could ask them for old manuals/docs and they'd charge you $$$ for it, but at least they'd still have it available 11-Mar-20 11:50 AM maybe it's because xp power bought them and now trombone fart 'buy a new one' 11-Mar-20 12:11 PM OH hey! I had that exact same problem 11-Mar-20 12:11 PM With glassman. 11-Mar-20 12:12 PM grumble 11-Mar-20 12:12 PM guess i'll have to borrow the missus as a spotter while i dive in in one-handed 11-Mar-20 12:26 PM @idmb .. i assume you mean re: requesting docs, not the problem i'm having in that thread, right? 11-Mar-20 12:33 PM With a side order of they may have no one there they could even ask if they remember where the file with the manual in it is anymore. Definitely ran into that with Spectra Physics. 11-Mar-20 12:34 PM yeah, also plausible 11-Mar-20 12:34 PM meanwhile I pinged Canberra about a 40-year-old System 35+ multichannel analyzer and I had a PDF manual in ~hours. at least some folks've got it together 11-Mar-20 12:38 PM Requesting docs. I asked for "whatever spec sheets or catalogue archives they have" and they just said "it's obsolete, we don't provide info for out of date products." 11-Mar-20 12:38 PM It felt like a pretty snarky "Why would you even ask?" question 11-Mar-20 12:38 PM when I emailed pfeiffer about a manual for an ancient turbo they sent it to me the next day with an apology about the quality 11-Mar-20 12:39 PM leybold on the phone offered to mail me an old catalogue 11-Mar-20 12:39 PM but that they wouldn't provide a PDF 11-Mar-20 12:39 PM idealvac had it so eh 11-Mar-20 12:41 PM that reminds me, i managed to get a hold of the enormous original blueprints for my spellman 30kv 1mA power supply, i need to find a large-format scanner and upload them someplace 11-Mar-20 12:41 PM Ludlum also falls firmly in the has it together category. 11-Mar-20 12:41 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-06E34.png 11-Mar-20 12:41 PM @qualia DSLR scans are surprisingly good, if you have one I would do that ASAP "just in case" 11-Mar-20 12:41 PM (i mailed them and asked them for info and they told me to buzz off in rather ruder terms, so this's also partially out of spite ^.^) 11-Mar-20 12:41 PM oh yeah definitely 11-Mar-20 12:45 PM Does anyone have an idea what the best way to maximize power out of a BBO is? 11-Mar-20 12:45 PM I have the insane amount of 800nm and can set it to pretty much anything from 200fs to 500 ps 11-Mar-20 12:45 PM And will then always be trying to work at "just enough intensity not to damage the BBO 11-Mar-20 12:45 PM so it will be balancing peak intensity with the total pulse length in terms of damage 11-Mar-20 03:21 PM Just caught up now. That person making ruby with an arc welder and the improvised eyepro… I know the UV is probably more of a health risk, but isn't it also a pretty bad idea to vaporize chromium where you put your lungs? 11-Mar-20 03:22 PM So I realized the best way to get more energy without thinking 11-Mar-20 03:22 PM Is split my 800nm before attenuating, focus each onto a separate bbo, then recombine on the ruby 11-Mar-20 03:22 PM #lifehack 11-Mar-20 09:43 PM any suggestions on a monochromatic light to get to test flatness via optical flat? 12-Mar-20 09:06 AM sodium lamp? 12-Mar-20 09:28 AM So, turns out the smudge was actually ablated brass 12-Mar-20 09:28 AM So I guess we'll see if it's a problem 12-Mar-20 09:28 AM I'd also agree that sodium lamp is probably the easiest monochromatic light to get your hands on 12-Mar-20 09:30 AM Paul Corkum’s talk at DAMOP 2020: “Using light to control electrons to create new light” 12-Mar-20 05:28 PM so, thorlabs has aluminum-coated and silver-coated mirrors 12-Mar-20 05:28 PM and they seem to cost the same, but silver has better reflectivity? i guess 12-Mar-20 05:28 PM are aluminum mirrors preferred for some applications? 12-Mar-20 05:30 PM UV 12-Mar-20 05:30 PM silver is garbage below ~350nm 12-Mar-20 05:30 PM If you actually have a plan (wavelengths/polarizations etc) and care about efficiency, the dielectrics are a little more expensive and a lot better than silver 12-Mar-20 05:30 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-3336D.png 12-Mar-20 05:36 PM some flexibility would be nice; the primary use is 632.8nm laser schlieren but white light is also of interest 12-Mar-20 05:36 PM but i considered it 12-Mar-20 05:36 PM they conveniently cut off the graphs on their website 12-Mar-20 05:36 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Protected_Silver_Reflectance_12deg_G2-370-89CA6.png 12-Mar-20 05:36 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Protected_Aluminum_Reflectance_12deg_G2-40-9F9CD.png 12-Mar-20 05:36 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-927B8.png 12-Mar-20 05:39 PM what's the deal with that funky cutoff point up in the infrared? 12-Mar-20 05:39 PM or, not cutoff, but that transition 12-Mar-20 05:44 PM No idea 12-Mar-20 05:44 PM the only stuff I touch above 800nm are the leaky YAGs 12-Mar-20 05:58 PM infrared's weird 12-Mar-20 06:11 PM my guess is that strange transition is a different instrument 12-Mar-20 06:11 PM I would guess that UV to FIR is probably not all done on the same instrument 12-Mar-20 06:42 PM Oh, agreed 13-Mar-20 07:20 PM Cheap camera for viewing 1090nm beam? 13-Mar-20 07:20 PM Pi NoIR can’t do it well 13-Mar-20 07:20 PM Silicon nonsense 14-Mar-20 07:31 PM is there a standard product line (such as HP 5xxx) of a laser interferrometer system that I should look at - for length/position calibration 14-Mar-20 07:42 PM I suppose sam has complete kits with everything requested for not ridiculous amount - and prob great customer service for hobbyists 14-Mar-20 08:11 PM hrm, okay, another thing added to the list of equipment to get (and nice it is so easy with a kit from him) 14-Mar-20 10:30 PM oh huh. i got a gift card bonus.. thing, from work.. and one of those kits has been in my wishlist for a while now 14-Mar-20 10:30 PM @idmb no idea if it's usable at that wavelength, but playstation eye USB cameras are like $7 and are IR responsive 14-Mar-20 10:59 PM Most definitely won’t do much above ~900nm 14-Mar-20 10:59 PM Sadly 14-Mar-20 10:59 PM It’s the silicon sensor. Photon energy incompatible 15-Mar-20 01:24 AM ah dang 15-Mar-20 05:14 PM Friends are always here to help raise my blood pressure. https://twitter.com/ancients/status/1239334363579346944?s=21 16-Mar-20 05:30 AM USB cameras without IR filters are quite sensitive in IR. I see 1064nm with them routinely. There is tiny bit of sensitivity at 1100nm left, but not much. If you really need to go up to 1100 - you can heat detector to ~80°C. 16-Mar-20 05:30 AM Heat, not cool 16-Mar-20 06:54 AM oo, that's good to know. 16-Mar-20 11:42 AM This purple light is ~1064nm via regular phone, strong enough to shoot through IR filter.. This does not feel very safe though (1700W peak power). 16-Mar-20 11:42 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/fiber-laser-C363A.png 16-Mar-20 12:05 PM that is very pretty and very scary 16-Mar-20 03:41 PM Is it possible to get a visible wavelength bandpass filter that doesn't need edge protection? 17-Mar-20 05:03 AM @piGuy It's a question of design, specifications and price. One can stack many dielectric filters on top of each other. For example, there are astronomy (RGB and narrow-line) filters of both types - with and without IR-cut feature. 18-Mar-20 05:00 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200318_125647-20AFF.jpg 18-Mar-20 05:00 AM my hybrid pmt got some optics today! 18-Mar-20 05:00 AM but I still don't really know what to do with it 18-Mar-20 10:05 AM @Mezmorizor my class just covered OPAs and OPOs today 18-Mar-20 10:05 AM to me it seems all nonlinear optics can be summarized by "give it as much power as you can without damaging it, if you can seed it that's a win, angle often matters" 18-Mar-20 10:18 AM That's pretty much it. And "please make note of when your optic decides not be one anymore, that will help set limits for products from a given manufacturer." 18-Mar-20 11:28 AM That's basically it yeah. A lot of considerations when you're actually designing stuff because beam shape, group velocity dispersion, focused vs collimated beam, etc. all matter a lot for phase matching, but practically using something it's all about that angle most of the time 18-Mar-20 11:28 AM And yeah, I've definitely had companies tell us "yeah, I don't actually know when it breaks. Could you tell us when it happened if it happens?" 18-Mar-20 11:28 AM Also went over it in laser physics I assume? 18-Mar-20 11:30 AM Yeah that's the only class I'm in 18-Mar-20 11:31 AM Oh, I guess that makes sense 18-Mar-20 05:56 PM Anyone here know a good resource on kohler illumination for a metallographic microscope? Trying to build one but unsure about where the different focal planes are supposed to be 18-Mar-20 05:56 PM Currently i have the field stop iris at approximately the image plane of the objective+field lens 18-Mar-20 05:56 PM But wrt the aperture stop and collecting lens, resources seem to be contradictory 18-Mar-20 05:58 PM @Nixie might, I think he DIYed something here 18-Mar-20 06:02 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/P1010404-828B2.jpeg 18-Mar-20 06:02 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/P1010398-FADFD.jpeg 18-Mar-20 06:02 PM Thats my setup currently 19-Mar-20 01:14 AM Nah, I just attached a giant 100W led to my microscope, nothing fancy at all: 19-Mar-20 01:14 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/EPmNQBRWoAA5Ac--61CE1.png 19-Mar-20 07:58 AM It already had a beamsplitter? 19-Mar-20 12:18 PM Yes. 20-Mar-20 02:19 AM @pbx/peterbjornx I really hope you are working on infinity microscope. It will forgive you alot of errors. In it's case it will be easy - no focal planes outside of illumination unit. Doing finite-tube microscopes (like 160mm ones) will require precise alignment and could be hard to do without CNC manufacturing/metrology. If you just starting and is on finite tube - you should really move to infinite gear. 24-Mar-20 11:00 AM anyone by chance know a Lukas Bochtler? Sounds like they might be interested to collaborate to microwiki.org. They've started a similar project here and just reached out to me: http://microwiki.ddns.net/index.php/Main_Page 24-Mar-20 11:06 AM quite ambitious 03-Apr-20 01:44 PM https://www.rp-photonics.com/spotlight_2020_03_16.html 03-Apr-20 01:44 PM fun article 04-Apr-20 04:49 PM RIP my poor laser's alignment 04-Apr-20 04:49 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/JPEG_20200404_194900-DD47A.jpg 04-Apr-20 04:50 PM nice flashlight 04-Apr-20 04:52 PM Luckily it's just mainly the output lens mounted on a slightly crooked plate 04-Apr-20 04:52 PM Phone's camera doesn't pick up the spot very well right before the lens 04-Apr-20 04:52 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/JPEG_20200404_195256-FDA6A.jpg 04-Apr-20 04:52 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/JPEG_20200404_195505-4A262.png 04-Apr-20 05:10 PM I love push to connect fittings 04-Apr-20 05:10 PM but it kind of terrifies me that they use them in lasers 04-Apr-20 05:12 PM The funny thing is the push to connect goes to super beefy industrial water fittings on the outside 04-Apr-20 05:12 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20200404_201538-1FB12.jpg 04-Apr-20 05:12 PM Shipping has not been kind to this poor laser ️ 04-Apr-20 05:23 PM Sometimes it makes me wonder if they literally drove over this thing with a forklift 04-Apr-20 05:23 PM The whole 1.5" thick aluminum baseplate with a T-slot is bent, it doesn't sit flat on the bench and both end plates were dented 04-Apr-20 05:27 PM wait 04-Apr-20 05:27 PM what kind of laser has a 1.5" baseplate? 04-Apr-20 05:27 PM even my giant amp is only on a low-end 2" breadboard 04-Apr-20 05:29 PM This is a 50W Q-switched, DPSS Nd:YAG. The base plate has t-slots on both sides 04-Apr-20 05:29 PM It's a fully enclosed and contained unit, for use on industrial engraving machines, not on optical tables 04-Apr-20 05:31 PM ah 04-Apr-20 05:31 PM 50W IR I gather? 04-Apr-20 05:32 PM 1064 nm, pumping diode at 808 nm require ~650 W to 800 W electrical power input 04-Apr-20 05:33 PM yeah ours requires 50A/200V 04-Apr-20 05:33 PM for like 15W 532nm 04-Apr-20 05:33 PM 50Hz Quanta Ray. Doesn't have anything like that baseplate 04-Apr-20 05:34 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20200404_203426-082AE.jpg 04-Apr-20 05:34 PM Getting some better results now. This is with a 1mm aperture, spot is 4 meters away from the output lens 04-Apr-20 05:35 PM what are you wanting to use it for? 04-Apr-20 05:37 PM Initially, what it was intended for, engraving/micromachining on any material 04-Apr-20 05:37 PM Later on, depending on how far I can push the q-switch, maybe some laser welding 04-Apr-20 05:37 PM I think the fact that I have a q-switch in the path means that I will never get a perfect spot. Always will be some aberration, so I'm happy for now. Aligning the IR beam will be more tricky 04-Apr-20 05:37 PM Here's the (2nd hand) galvanometer and f-theta lens I got for the engraving system, driving this thing has proven to be a nightmare 04-Apr-20 05:37 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/JPEG_20200309_210042-42E16.png 06-Apr-20 08:25 PM https://www.ebay.com/itm/Light-Laser-Power-Sensor-BNC-Scientific-Medical-/133370333023 06-Apr-20 08:25 PM So is this a thermopile sensor? Or pyroelectric? Photodiode even? 06-Apr-20 08:25 PM Seems awfully shiny for a thermopile sensor... 08-Apr-20 09:42 AM https://twitter.com/nixie_guy/status/1247556333294977024 08-Apr-20 09:44 AM omg 08-Apr-20 09:44 AM the tiny rails from mcmaster! 08-Apr-20 10:08 AM Nope, Aliexpress. I can't buy from Mcmaster in spain. 08-Apr-20 10:08 AM Big one is 7mm wide, small one is 5mm wide. 08-Apr-20 10:08 AM Personally, I would have preferred to have the bottom one be 5mm and the top one 3mm, but the pricing on the 3mm is just too much. 08-Apr-20 10:12 AM oh those are way bigger 08-Apr-20 10:12 AM the mcmaster ones are 1mm 08-Apr-20 10:12 AM WHAT 08-Apr-20 10:12 AM 1mm wide linear rails???? 08-Apr-20 10:12 AM THE WHAT???? 08-Apr-20 10:13 AM https://www.mcmaster.com/8381k28 08-Apr-20 10:13 AM so cute 08-Apr-20 10:13 AM OMG 08-Apr-20 10:13 AM How do you even attach that rail to something... 08-Apr-20 10:13 AM does it have bottom screws? 08-Apr-20 10:15 AM https://www.mcmaster.com/8381k9 08-Apr-20 10:15 AM you buy a bracket 08-Apr-20 10:15 AM XDDD 08-Apr-20 10:15 AM That's insane 08-Apr-20 10:15 AM (in a good way) 08-Apr-20 10:15 AM the 2mm rails have m1 mounting holes in the rail 08-Apr-20 10:16 AM Oh well, can't afford any 08-Apr-20 10:16 AM but indeed it is amazing 08-Apr-20 12:36 PM @Nixie link to the rails you bought? Did you get leadscrews too? 08-Apr-20 01:18 PM https://www.aliexpress.com/item/4000311607112.html?spm=a2g0s.8937460.0.0.44362e0e4xRCYw 08-Apr-20 01:18 PM I I want to use these steppers: 08-Apr-20 01:18 PM https://www.aliexpress.com/item/4000494175820.html?spm=a2g0s.9042311.0.0.341d4c4dTpqokX 08-Apr-20 01:36 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200408_223501-D6F31.jpg 08-Apr-20 01:36 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200408_223513-D5FBA.jpg 08-Apr-20 01:36 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200408_223548-5E970.jpg 08-Apr-20 01:36 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200408_223557-77C3A.jpg 08-Apr-20 01:36 PM biiiig monochromator 08-Apr-20 01:40 PM that's a weird slit design I haven't seen before 08-Apr-20 01:40 PM you can control height and width iirc 08-Apr-20 01:40 PM yeah you can on most 08-Apr-20 01:40 PM it's just often a V shaped thing you push in and out for height 08-Apr-20 01:40 PM and then a micrometer for width 08-Apr-20 01:41 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200408_224102-38BAA.jpg 08-Apr-20 01:41 PM OH 08-Apr-20 01:41 PM motorized 08-Apr-20 01:41 PM nice 08-Apr-20 01:41 PM heigt 08-Apr-20 01:41 PM is this yours? 08-Apr-20 01:41 PM how does that grating rotate? stepper? 08-Apr-20 01:43 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200408_224241-304FF.jpg 08-Apr-20 01:43 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200408_224251-0C5E7.jpg 08-Apr-20 01:43 PM stepper and a veeeery fine pitched leadscrew with a lever 08-Apr-20 01:43 PM it is mine, but I'm trying to cange that 08-Apr-20 01:44 PM it looks kinda janky 08-Apr-20 01:44 PM but with some well done stuff too 08-Apr-20 01:44 PM what company? 08-Apr-20 01:46 PM it came from someone who modified a lot of devices in a questionable way 08-Apr-20 01:46 PM spetec gmbh 08-Apr-20 01:47 PM why do you wanna get rid of it? 08-Apr-20 01:48 PM because it takes up space and would require a lot of effort to get going 08-Apr-20 01:48 PM I just don't need it 08-Apr-20 01:48 PM adjustable slit - concave mirror - grating on rotation mount - concave mirror, all in an enclosure... nice 08-Apr-20 01:48 PM if the slit controls work it actually should be super easy to set up? 08-Apr-20 01:49 PM yeah it's like 1.5m path length, maybe 500 pm fwhm should be doable 08-Apr-20 01:49 PM what's the grating groove density? 08-Apr-20 01:49 PM but I'd need a 5 phase steller controller, some readout for the pmt, a software to display the spectra 08-Apr-20 01:49 PM no idea 08-Apr-20 01:49 PM replace pmt with CCD ? 08-Apr-20 01:50 PM the PMT is the least of my issues, I was talking about digitizing it and feeding the signal to some software 08-Apr-20 01:50 PM and I just don't need it 08-Apr-20 01:50 PM you don't need the stepper controller if you use a CCD 08-Apr-20 01:50 PM since you no longer have to scan 08-Apr-20 01:51 PM I do, the "spread" of the grating has an angle so big the second mirror only sees a tiny part of it 08-Apr-20 01:51 PM so I could replace the second mirror with a detector closer to the grating, but then I'd lose the advantage of such a long path 08-Apr-20 01:51 PM and at that point I could build a smaller easier to use spectrometer myself 08-Apr-20 01:52 PM depends on wavelength/bandwidth 08-Apr-20 01:52 PM but yeah 08-Apr-20 01:52 PM the point of this one would be sensitivity 08-Apr-20 01:52 PM it had a pmt made for photon counting on it 08-Apr-20 01:53 PM Yeah 08-Apr-20 01:53 PM I meant the giant box 08-Apr-20 01:53 PM if you come pick it up in munich you can demonstrate to us all how to get it going 08-Apr-20 01:53 PM a smaller easier to use spectrometer will be a lot less sensitive 08-Apr-20 01:54 PM and I just don't need the sensitivity 08-Apr-20 01:54 PM or an optical spectrometer at all 08-Apr-20 01:54 PM but I got it for really cheap and it was kind of an impulse buy 08-Apr-20 01:54 PM but now I want more space on my table 08-Apr-20 01:55 PM can you tell the make / model of grating? 08-Apr-20 01:55 PM looks aluminum to me so meh 08-Apr-20 01:55 PM but the gold ones are worth quite a bit 08-Apr-20 01:55 PM at any groove density 08-Apr-20 01:56 PM lemme see if I can remvove it 08-Apr-20 01:56 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200408_225814-D06CE.jpg 08-Apr-20 01:56 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200408_225851-EC4BF.jpg 08-Apr-20 02:00 PM can't read what it says the blazing is 08-Apr-20 02:00 PM but yeah at 2400 grooves/mm that's almost the limit for 800nm 08-Apr-20 02:01 PM 1700500 A° it says 08-Apr-20 02:01 PM what's blazing in this context? 08-Apr-20 02:02 PM it tells you the wavelength it's optimized for, that ones is 500nm and 1700nm 08-Apr-20 02:02 PM the grating isn't symmetric / the grooves have a certain depth 08-Apr-20 02:03 PM ahh, I see 08-Apr-20 02:05 PM actually I'm confused about the 1700 08-Apr-20 02:05 PM oh no, thorlabs have 1600nm gratings so that's probably right 08-Apr-20 02:06 PM maybe it means 1700 to 5000 Angström 08-Apr-20 02:06 PM it has a port to be flooded and is gas tight 08-Apr-20 02:06 PM but I don't think you can diffract 1700nm with 2400 lines/mm 08-Apr-20 02:06 PM so maybe it can be flooded with some gas that transmits deep UV? 08-Apr-20 02:08 PM or maybe they're actually telling the dimensions of the blazing 08-Apr-20 02:08 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-4811B.png 08-Apr-20 02:08 PM that might make sense, I remember being confused the first time I tried it, because the movement range only covered part of the optical spectrum 08-Apr-20 02:08 PM X and Y 08-Apr-20 02:08 PM your guess is as good as mine 08-Apr-20 02:08 PM or even better, as you seem to know a bit about those things 08-Apr-20 02:09 PM these are all I use: https://www.spectrogon.com/product-services/gratings/pulse-compression-gratings/ 08-Apr-20 02:09 PM they provide a handy transmission and input angle efficiency guide 08-Apr-20 02:09 PM anyways, don't damage or scrap the grating! 08-Apr-20 02:11 PM I wasn't going to ^^ 08-Apr-20 02:11 PM it's back in its place 08-Apr-20 02:11 PM I just decided to take some pics of the thing because a friend of mine might be interested in it and it's moving place in the workshop 08-Apr-20 02:11 PM and it's at least 40 kgs, so it doesn't get moved very often 09-Apr-20 12:10 PM Have a laser safety question.... 09-Apr-20 12:10 PM The makerspace is currently closed except for a very limited number of people making PPE for COVID-19 response. 09-Apr-20 12:10 PM We have a 150 watt Boss laser cutter. 09-Apr-20 12:10 PM The laser has doors for material feedthrough. We’re looking at using them to pass though plastic sheet from a roll. 09-Apr-20 12:10 PM Nobody is going to look in through the open door at the spot. 09-Apr-20 12:13 PM Is that useful? I thought the doors were normally just so you could cut from oversized material 09-Apr-20 12:13 PM How can you efficiently cut from a roll and remove material? 09-Apr-20 12:14 PM Leave tabs so it goes from roll to roll? Or open the top door at the end of the cut, pull out the cut pieces, and advance the roll out the other side which will be scrap, close the door and repeat? 09-Apr-20 12:15 PM Ooh, okay that actually sounds pretty nice. 09-Apr-20 12:15 PM I didn't think of tabs + rolling it up again. 09-Apr-20 12:15 PM Actually - that probably wouldn't work well ? Unless you had a ton of tabs. Bending it would pop them out 09-Apr-20 12:17 PM I’m wondering about risk of eye damage here. The space is locked down tight. So we don’t have to worry about someone not involved in the project staring through the open doors. 09-Apr-20 12:17 PM That cutter has the standard metal honeycomb design below the material, right? 09-Apr-20 12:17 PM I’m wondering about whether any laser emanation from there could indirectly pose a risk. 09-Apr-20 12:17 PM Yes, honeycomb. 09-Apr-20 12:18 PM And they warp a bit, right? 09-Apr-20 12:18 PM Slightly. 09-Apr-20 12:18 PM This isn’t precision. We are optimizing for volume. Cutting face shields and head bands. 09-Apr-20 12:19 PM So there is the possibility of them redirectly light out of the chassis, which gets more probable as you run it more. It's a 150W CO2 laser, right? 09-Apr-20 12:20 PM https://sites.google.com/cps.edu/ltmakers/solin-flatpack-face-shield 09-Apr-20 12:20 PM Yes, 150 watt CO2. 09-Apr-20 12:20 PM Normally, if other people were in the space, I’d feel differently, but this is a highly controlled environment with operators who will be trained and can be trusted not to do stupid things. 09-Apr-20 12:21 PM Well then I believe the honeycombs getting destroyed are the main concern in terms of beams going wild 09-Apr-20 12:21 PM because even with the feedthrough, nobody will be staring at the spot directly 09-Apr-20 12:22 PM That’s what I thought. 09-Apr-20 12:22 PM the jig to keep the rolled sheet flat-ish sounds kinda difficult? 09-Apr-20 12:22 PM If you stack acrylic on a lasercutter, does it melt the layers together or does it work well? 09-Apr-20 12:23 PM Two bars of metal on either side of the cutting area will hold it down. 09-Apr-20 12:24 PM Unless rolls are much cheaper than sheets I'm just not sure this will end up being faster than having someone swap out sheets 09-Apr-20 12:24 PM I’m so sad the honeycomb is Al. I know someone with a steel honeycomb. That was a thing of beauty - because those ridiculously strong hard drive magnets would hold even warped 1/8” plywood flat. 09-Apr-20 12:24 PM since the setup / troubleshooting will be quite substantial 09-Apr-20 12:24 PM but maybe I'm just not imagining it right - got a video of someone cutting from a roll? 09-Apr-20 12:26 PM We’re looking at both options, but I’m expecting a bulk roll will be cheaper than cut sheets. Also, it saves on material. After the cut, you only advance the roll by what you need. With a large sheet, you lose more waste as the design doesn’t take up a full sheet. 09-Apr-20 12:27 PM Yeah I have no doubt that for a long-term industrial setting a roll makes more sense 09-Apr-20 12:40 PM also for cutting that you're surely running well below 150W, even at high speed? 09-Apr-20 12:40 PM Probably, yes. 09-Apr-20 12:42 PM and the lens focal length isn't something like 2cm, meaning that if the acrylic got bungled up and diverted it (somehow? don't know the construction of your machine) it wouldn't be able to easily divert the final mirror + lens? 09-Apr-20 12:42 PM (assuming the gantry thing with the lens is only as close to the cutting material as the focal length) 09-Apr-20 12:42 PM heck you might just have a galvanometer instead of a gantry, didn't think of that. 09-Apr-20 12:44 PM The lens rides on the gantry. 09-Apr-20 12:53 PM yeah but is the gantry really close to the material, or a few cm away? 09-Apr-20 12:58 PM I think it’s a few cm away. 09-Apr-20 01:16 PM Can you just drape a cloth? 09-Apr-20 01:16 PM Over the opening 09-Apr-20 01:24 PM I assumed the feedthrough had something like that 09-Apr-20 09:11 PM CO2 cutter? Wear your polycarb safety glasses at all times and you'll be fine for scattered 10.6 micron. While I can't officially tell you that your normal shop safety glasses are adequate laser safety eyewear for a CO2 system @rdpierce, experience and testing says they do OD 6 or better. 09-Apr-20 10:11 PM Thanks, @funranium . That would work. Because we have a lot of control over the building now, we don't have to worry about people walking in who don't know what's going on. 09-Apr-20 10:11 PM So we can mandate safety glasses and not have to worry about idiots ignoring the warning. 10-Apr-20 08:55 AM If you feel like sacrificing a pair, putting the beam at low power and a power meter at the other side you can always test to feel more comfortable. 10-Apr-20 09:54 AM Related: @funranium do you know of any studies where they've used already-blind people to do damage analysis with lasers? 10-Apr-20 10:52 AM In what way? There might be interesting discussions with ethics people about that. 10-Apr-20 11:00 AM indeed 10-Apr-20 11:00 AM https://www.news-medical.net/health/Growing-an-eye-for-transplantation-potentials-and-pitfalls.aspx 10-Apr-20 12:24 PM just yesterday i was telling my partner 'You proooobably shouldn't assume we'll just have eye/ear transplants as a Thing' re: wearing appropriate PPE, guess it's closer than I thought 10-Apr-20 12:24 PM (apparently, sawzalling a 55-gallon drum in half is Loud. whod've thought) 10-Apr-20 12:31 PM I wanted to look up how big that is 10-Apr-20 12:31 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-02B0D.png 10-Apr-20 12:31 PM google knows me too well 10-Apr-20 12:32 PM :D 10-Apr-20 12:47 PM don't pretend like you don't know how big that is 10-Apr-20 12:48 PM Oh lord 10-Apr-20 12:48 PM one (1) half life explosive barrel's worth 10-Apr-20 12:49 PM I live in germany, I cannot tell you how much a gallon is 10-Apr-20 12:49 PM https://www.amazon.com/LubeLife-Personal-Lubricant-Lube-Parabens/dp/B07FMGNV51?th=1 10-Apr-20 12:50 PM don't give me any ideas 10-Apr-20 12:50 PM and don't drift off too off topic 10-Apr-20 12:50 PM Sounds like a good party if one of those is needed. 10-Apr-20 12:50 PM i'll move that to #resources 10-Apr-20 03:28 PM @samy LOL... Who takes a 55 gallon drum to the water park??????? 10-Apr-20 03:28 PM the answers are also amazing 10-Apr-20 03:43 PM I don't judge 10-Apr-20 03:43 PM I got an ebay optical flat...realized I don't have a monochromatic light source for it. has anyone tried a laser pointer as one? 10-Apr-20 04:48 PM How big is the flat? I think you'd probably want to expand the beam to a much larger diameter and then collimate it 10-Apr-20 05:14 PM makes sense, going to make a diffuser and give it a shot. ~50mm 10-Apr-20 05:16 PM a diffuser? you're going to scatter the light? 10-Apr-20 05:16 PM I think you want beam expander optics so the light will stay coherent 10-Apr-20 05:16 PM (I'm not an optics expert though, I just fake it till I make it) 10-Apr-20 05:19 PM i assumed it only needed to be monochromatic, not coherent...but i know nothing of this stuff 10-Apr-20 06:31 PM To use it for interferometry or flatness testing, you need coherent 10-Apr-20 06:31 PM If you just want less aberration in an optical microscope, not coherent is fine 10-Apr-20 06:31 PM I.e. avoiding chromatic abberation 10-Apr-20 08:10 PM i see 11-Apr-20 12:36 PM Was able to get this by diffusing+reflecting laser diode light 11-Apr-20 12:36 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_9191-0EC1D.JPG 11-Apr-20 01:09 PM Hrmm, then I failed the optics quiz I guess 11-Apr-20 01:09 PM Now to think of it, a microscope I use every few months has differential interference contrast optics, and just uses a normal lamp 11-Apr-20 08:12 PM I don't know anything about optics...I don't understand coherence, or even why those lines show up, looking forward to reading up on it 11-Apr-20 08:58 PM https://phet.colorado.edu/en/simulation/legacy/lasers 11-Apr-20 08:58 PM A cute monte-carlo laser "simulation" program 11-Apr-20 08:58 PM Interesting that I can't actually get population inversion, even for a laser that's about to blow up 11-Apr-20 08:58 PM Probably due to the unrealistic ratios used between photon lifetime and the lifetimes of the excited states 11-Apr-20 09:42 PM Yeah you can? 11-Apr-20 09:43 PM As you can see most of the atoms are in their ground state 11-Apr-20 09:43 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/extreme-5796F.PNG 11-Apr-20 09:43 PM And this is just before it "blows up" 11-Apr-20 09:44 PM You can even q-switch it 11-Apr-20 09:44 PM This is just before I q-switched it yeah 11-Apr-20 09:45 PM but until you get steady state 11-Apr-20 09:45 PM levels 2 and 1 are just oscillating a ton 11-Apr-20 09:45 PM you have periodic population inversion, real lasers do that too if you set them up wrong 11-Apr-20 09:45 PM lower the state energies, the damage threshold is more of a problem with higher energy photons 11-Apr-20 09:47 PM Shouldn't I definitely get population inversion though in this run-away situation? I tried to pause the simulation randomly in steady-state and there was never population inversion 11-Apr-20 09:47 PM Hmm, lower state energies certainly does help, but I think population inversion should be independent of state energy separations or how many different levels there are 11-Apr-20 09:47 PM Not that this is meant to be realistic of course 11-Apr-20 09:47 PM Now I want to build my own Monte-Carlo simulation for a laser! 11-Apr-20 09:49 PM it depends how "lamp control" works 11-Apr-20 09:49 PM is it power, or # photons, or intensity? 11-Apr-20 09:50 PM It works in the same way as the laser, turn on the photon view for the lamp, it literally just shoots monochromatic photons at adjustable intensities into the laser 11-Apr-20 09:50 PM I mean is the slider range the same at different wavelengths 11-Apr-20 09:51 PM The slider just controls number of photons emitted by the lamp per second 11-Apr-20 09:51 PM Irrespective of wavelength 11-Apr-20 09:52 PM Hmm. Are 3-1 transitions allowed? 11-Apr-20 09:52 PM I'm trying to get a steady state 11-Apr-20 09:54 PM Not sure, I guess not 11-Apr-20 09:54 PM Set the lifetime of the highest state to very short, and 2nd to quite long, and you should be there 11-Apr-20 09:55 PM nah everything flickers a lot 11-Apr-20 09:55 PM I wish there was a time slider 11-Apr-20 09:57 PM It's a toy afterall. I can't find any serious Monte-Carlo simulations of a laser cavity, most of them are just on light-matter interaction stuff 11-Apr-20 09:57 PM Oh just found one 11-Apr-20 09:57 PM https://iopscience.iop.org/article/10.1088/1367-2630/aaec36 11-Apr-20 09:58 PM heh the best steady state output I can get 11-Apr-20 09:58 PM is with no inversion 11-Apr-20 09:58 PM I got the output power to go to the edge of where the danger line is 11-Apr-20 09:58 PM but that was playing with Q switching 11-Apr-20 09:58 PM yeah I can get about 1/4 bar basically steady state output, but in those cases it's without inversion :p 11-Apr-20 10:20 PM It does put into perspective just how rare spontaneous emission is compared to stimulated emission 11-Apr-20 10:20 PM One major flaw for this method is that it's going to be super random when it's just beginning to lase, since it is dependent on such a rare event. 11-Apr-20 10:20 PM Calculating how fast this happens is actually really interesting for me, because I think that's a limiting factor when pushing q-switch frequency super high 11-Apr-20 10:20 PM Which is probably necessary for welding and 3D printing metal at home 11-Apr-20 11:55 PM Is it? Afaik almost everything rep-rate related is limited by pumping 12-Apr-20 10:15 AM Pumping power is certainly a big factor in limiting the pulse energy, but unfortunately I can't do much to increase it due to thermal limitations, and peak power should actually be lower when I don't want to ablate material, but to join them. The randomness of seeding via spontaneous emission can also cause severe mode beating and thus inconsistent pulse-to-pulse energy, which is a problem when forming a consistent melt pool 12-Apr-20 10:15 AM So people have seeded their Nd:YAG pulses just to get rid of that oscillation 12-Apr-20 10:15 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/wbYykPMSJFKTihg0ExUax6OjLp5uMnYduPKvmfWONL-B37FF.png 12-Apr-20 10:15 AM Additionally, I think increases losses due to amplified spontaneous emission might limit scaling of average power as pumping power is pushed higher. 12-Apr-20 10:15 AM Basically, I am just trying to find out if I need to seed the laser at these high rep rates (~500kHz) 12-Apr-20 10:21 AM ASE has no gain clamping 12-Apr-20 10:21 AM so even though it can produce a beam and have ~the same average output power, it is ugly 12-Apr-20 10:22 AM Yeah, so it's effectively lost power for this application 12-Apr-20 10:23 AM What's causing your rep rate? 12-Apr-20 10:23 AM Q switch? 12-Apr-20 10:23 AM Yeah 12-Apr-20 10:24 AM passive? 12-Apr-20 10:24 AM It's rated up to >100kHz, although I think it can be pushed quite a bit further given the risetime and falltime specifications 12-Apr-20 10:24 AM No, active AOM 12-Apr-20 10:26 AM is yours like the example in that your bad spikes are just from a second mode? 12-Apr-20 10:26 AM or are there more? can you just select for one mode 12-Apr-20 10:27 AM I think it's going to be a lot uglier than that figure, because it's due to ASE and it's complete randomness 12-Apr-20 10:27 AM More like this 12-Apr-20 10:27 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/3-s2-7CA8F.png 12-Apr-20 10:30 AM ASE does a poor job of depleting energy in the gain medium though 12-Apr-20 10:30 AM typically the feedback / mode will dominate it by a lot 12-Apr-20 10:34 AM Well, I haven't done any math on this yet, just reading from papers and RF Photonics Encyclopedia. 12-Apr-20 10:34 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-8C6CA.png 12-Apr-20 10:34 AM So I only use YAGs for pumping TiSaphs, and the "problematic" one is pumping a regen amplifier with a round trip time of 1ns and about 9 round trips 12-Apr-20 10:35 AM Oh, femptosecond stuff? 12-Apr-20 10:35 AM Yeah. What I'm saying is I don't know what the quality of the YAG pulses actually is 12-Apr-20 10:35 AM (probably pretty good since they're 100k each but a nice gaussian isn't much better than one with ripples in this case) 12-Apr-20 10:37 AM It depends a lot on the resonator design too I guess, my round trip time is also about 1ns, but even at the highest frequency I need there's still hundreds or thousands of round trips 12-Apr-20 10:37 AM The thing is the ripples becomes more significant as the peak output power is reduced too 12-Apr-20 10:39 AM anyways that snippet's statement isn't entirely true. Even with no SE, lowering the rep rate would lower the average power as the pump would stop being absorbed when it saturation. So it's not just "this one factor" 12-Apr-20 10:41 AM Oh yeah, there's so many factors and math involved that I'm tempted to just try it 12-Apr-20 10:41 AM isn't your laser a commercial device? how do you just add a seed? 12-Apr-20 10:45 AM I can unbolt things and move components around on the rail, and it's a pretty standard T-slot mount. There is room between components, and I can also extend the whole thing by taking off the back cover plate 12-Apr-20 11:53 AM reading up to do a presentation on TiSaph simulations 12-Apr-20 11:53 AM Appleton Laboratory has developed a 35 TW, 2 ps laser. These systems all operate at low (a few pulses per hour) repetition rate 12-Apr-20 12:19 PM @Mason_Yu are those traces IR or 532nm? And if 532nm, what's the frequency doubler? 12-Apr-20 12:19 PM Just reading my MaiTai manual and it straight up says KTP introduces some terrible amplitude fluctuations so they use LBO 12-Apr-20 12:19 PM and the whole "do the frequency doubling in the cavity" thing 12-Apr-20 12:23 PM The second set of traces I sent comparing unseeded and seeded is 1064 IR from q-switched Nd:YAG 12-Apr-20 12:23 PM Damn. Yeah you can avoid making a more complicated mode-selective ("bad modelocking") cavity with the doubler inside. I assume for welding you want IR? 12-Apr-20 12:24 PM Yeah for sure, I also cannot afford nonlinear optics 12-Apr-20 12:25 PM couple more decades and hobbyists will figure that out 12-Apr-20 02:38 PM has anyone made diffraction gratings? 12-Apr-20 03:04 PM No, you can buy bad ones for very cheap and good ones are very hard to make 12-Apr-20 03:21 PM i'm trying to make a mold with diffraction grating on it so trying diff things 12-Apr-20 03:52 PM A mold with a grating on it... As in to cast gratings, or a mold that can be used as a diffraction grating? 12-Apr-20 03:52 PM (Are you just trying to 3D scan the mold?) 12-Apr-20 03:53 PM https://www.youtube.com/watch?v=SoTi0tM4yQ8 12-Apr-20 04:00 PM trying to make a mold to cast chocolate like that 12-Apr-20 04:00 PM he's using the diffraction grating directly but i'd like to get the grating imprinted on something else that i can reuse 12-Apr-20 04:01 PM try silicone 12-Apr-20 04:10 PM i tried a food safe two part rubber silicone...failed, but i don't think i waited long enough so will retry 12-Apr-20 04:10 PM but saw no diffraction at all on it, but i may need to try casting onto it first 12-Apr-20 04:10 PM chocolate on the other hand directly on the grating i got a little bit of diffraction 12-Apr-20 04:10 PM going to reattempt with some additional pressure 12-Apr-20 04:15 PM good luck! 12-Apr-20 04:33 PM I wonder if you could just do it with a laser 12-Apr-20 04:33 PM melt grooves 12-Apr-20 04:33 PM If all you want is the rainbow effect... Probably? 12-Apr-20 05:01 PM @idmb correct 12-Apr-20 05:01 PM i tried CO2 laser on delrin and making a bunch of tiny grooves, need to experiment more as i never got really tiny grooves 12-Apr-20 05:19 PM I made some grating ish things before with e beam,or rather had someone make it 12-Apr-20 05:19 PM Laser can also work if focused near the diffraction limit 12-Apr-20 05:19 PM @samy your optical flat band pattern can be used too 12-Apr-20 05:19 PM Reduce the size and project onto photoresist 12-Apr-20 05:19 PM That's how a lot of commercial gratings are started 12-Apr-20 05:19 PM The flat ones anyway 12-Apr-20 05:19 PM I don't think CO2 laser will be a small enough spot size 12-Apr-20 05:19 PM 405nm is better 12-Apr-20 05:27 PM ahh 12-Apr-20 05:27 PM reduce the size of what, the beam? so 405nm beam onto photoresist? 12-Apr-20 05:28 PM How did you have your CO2 setup for this? 12-Apr-20 05:51 PM Reduce the projected interference pattern image 12-Apr-20 05:51 PM I.e. a microscope or projector (or enlarger in photo film processing) in reverse 12-Apr-20 06:44 PM @idmb i just tried various power and speed settings...i'm using glowforge which i'm guessing automates a bunch of stuff? 12-Apr-20 09:27 PM You probably want extremely low power 12-Apr-20 09:27 PM And a smaller focus than the default? 12-Apr-20 09:31 PM Diffraction limit for co2 laser is gonna be right around 10.6 microns, so I think you'll end up with a relatively inefficient grating, but the bigger challenge is getting your line to line spacing in the sub-micron region 12-Apr-20 09:39 PM ahh 12-Apr-20 10:14 PM line to line spacing of 2um is fine 12-Apr-20 10:14 PM 500 lines/mm is a perfectly acceptable grating 12-Apr-20 10:14 PM but higher densities are from interference masks aren't they? 12-Apr-20 10:28 PM not sure what that is 12-Apr-20 11:06 PM @samy the optical flat pic you posted, with the zebra stripes, thats an interference pattern, which is presumably what @idmb meant 12-Apr-20 11:07 PM well not the optical flat specifically, but the same idea. 12-Apr-20 11:26 PM ahh so using an interference pattern to cut the gratings 13-Apr-20 12:53 AM Yeah, that's how a lot are mastered 13-Apr-20 12:53 AM If you want to stamp chocolate, you could take your exposed and developed photoresist, then sputter/evap metal, then electroform with nickel/etc 13-Apr-20 12:53 AM To get a reasonably thick and sturdy backing, like a couple to many hundred microns 13-Apr-20 12:53 AM Then hot glue that bad boy to a wooden dowel, and bam... Chocolate diffraction grating stamper 13-Apr-20 12:53 AM (please don't touch for any future cleaning of chocolate) 13-Apr-20 12:53 AM You can even bend such metal "shims", say around a dough roller 13-Apr-20 01:24 AM how do i actually create the pattern onto the photoresist? this would require 405nm laser? 13-Apr-20 01:30 AM Do you have any lenses that you can use to reduce that interference image you made? 13-Apr-20 01:30 AM It was monochromatic, right? 13-Apr-20 01:30 AM I mean the light source 13-Apr-20 01:43 AM i used a laser pointer without the lens, i could add the lens? 13-Apr-20 03:17 AM Try it 13-Apr-20 03:17 AM What did the optical setup look like for that? 13-Apr-20 03:17 AM Laser then diffuser then glass sitting on flat? 13-Apr-20 03:17 AM You might need to get a half-silvered mirror into the mix, to project the image of the interference pattern onto the photoresist 13-Apr-20 03:17 AM Alternatively, you could also rig up a DLP projector to a microscope at the eyepiece, and then you can basically just load up a zebra stripe image on that "extended desktop" 13-Apr-20 03:17 AM 405nm laser pointer in place of the original LED works well enough you can see the projected image with your eyes when the screen is a foot or two diagonally, from my memory 13-Apr-20 12:25 PM Laser -> "diffuser" (was a random semi-transparent 3d print I just had that fit nicely) -> reflecting off white paper -> optical flat sitting on glass table 13-Apr-20 12:59 PM @samy a pic would be helpful 13-Apr-20 12:59 PM @samy I've been wanting to play with decapping hologram stickers, and making copies of them 13-Apr-20 01:00 PM ooh interesting 13-Apr-20 01:00 PM on conf calls next few hours then will set up and take pic 13-Apr-20 01:03 PM http://www.nanomaker.com/nav.php?go=rainbowhol 13-Apr-20 01:03 PM Wanted to try making my own version of that software too 13-Apr-20 01:03 PM Make full-color diffraction images (aka holograms) 13-Apr-20 03:04 PM @idmb This is what I get for spending a weekend away from most media. For the recreational value of just burning holes in tissue, we tend not to do that with live subjects, much less human ones. Cow and rabbit eyes from the butcher for the most part to determine damage thresholds & mechanisms. Now, for the therapeutic side of the house there are lots of papers that involve laser use on "blind" eyes. "Blind" comes in a lot of flavors and some of them are more image processing issues than non-functional retinal or optic nerve issues. Which is to say, yes, even if you are blind already you should still wear laser safety glasses lest you become more and differently blind. 14-Apr-20 09:49 AM lol this isn't really useful but @Mason_Yu I found another laser simulator https://www.olympus-lifescience.com/en/microscope-resource/primer/java/lasers/tsunami/ 14-Apr-20 09:53 AM Too many bounces for my eyes 14-Apr-20 09:53 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/3x-AC22F.png 14-Apr-20 09:54 AM I saw it load and thought "this is cool" and then I saw what the sliders did and got sad 14-Apr-20 09:54 AM Getting GIFs on discord is apparently hard 14-Apr-20 09:54 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/monkainsane-32BC9.gif 14-Apr-20 10:05 AM that applet doesn't even seem right 14-Apr-20 10:05 AM Eh, close enough I guess. 16-Apr-20 12:56 PM 5x objective for toolmakers microscope arrived! Those phone pixels are now super easy to navigate. If I pull out an old phone I may be able to get a photo of 150x 16-Apr-20 01:21 PM hunting for a spectra physics 2040e argon laser manual... My google-fu is failing, anyone got one? 16-Apr-20 03:22 PM Made myself a piezo focus stage 16-Apr-20 03:22 PM 4 stacked piezo "speakers 16-Apr-20 03:27 PM Nice! 16-Apr-20 03:41 PM i can now focus individual layers in an ic 16-Apr-20 03:41 PM just by turning a lab power supply voltage knob 16-Apr-20 03:42 PM now make a feedback loop and have it autofocus 16-Apr-20 07:00 PM @pbx/peterbjornx Photos of how to mounted it please? 17-Apr-20 10:27 AM https://revspace.nl/kiekjes/view/20200417/P1010438.JPG its just a quick prototype 17-Apr-20 10:47 AM https://www.youtube.com/watch?v=LLtRRqwzdDI 17-Apr-20 10:47 AM did not realize those systems were such simple arrangements of a light and a couple mirrors 17-Apr-20 11:20 AM oh this is lovely 17-Apr-20 11:20 AM so that's how they do two-color schlieren 17-Apr-20 11:57 AM Yeah schlieren is surprisingly simple. The only hard part is to get the large mirrors. 17-Apr-20 02:15 PM Was thinking about that video while cleaning my work bench off a bit and I wonder if that would give any interesting visualizations of @Applied_Ion 's thrusters 17-Apr-20 02:17 PM I actually have thought about doing schlieren for the thrusters lol, I think I have seen it used for looking at stuff like plasma densities. You can get the right mirrors for not to expensive on eBay 17-Apr-20 02:19 PM I was thinking of playing with it a bit and setting up some vacuum formed mylar mirrors for a super low cost test setup 17-Apr-20 02:27 PM I don't think the differences in index of refractions would be enough in low pressure plasma 17-Apr-20 02:27 PM Might be wrong tho 17-Apr-20 02:27 PM For thrusters people have been using microwave or THz to get density 17-Apr-20 02:40 PM I've been considering using a 1 wire schlieren screen to do fast z-pinch plasma imaging. That was also one use I have in mind for my laser in conjunction with the fast framing camera 17-Apr-20 02:40 PM Need a frequency doubler to get 532nm laser though 17-Apr-20 02:40 PM I think pulse widths measured in a few nanoseconds should be possible with my set-up 17-Apr-20 02:40 PM And the gain of the intensifier tube is pretty incredible, so I hope I will be able to resolve features instead of just a complete blur 17-Apr-20 02:40 PM But yeah, for low density plasma it will be difficult to see obvious patterns, I think a Langmuir probe that can be moved around the thruster would provide more useful data 17-Apr-20 02:40 PM That's unfortunately not really an option for me though 17-Apr-20 02:52 PM Probes tend to disturb things a lot depending on what kind of thrusters you are talking about and where you measure. The cools kids now do LIF or even Thomson scattering 17-Apr-20 02:54 PM you can also do schlieren with fresnel lenses -- i grabbed a pair of Old Fart Magnifying Sheets and have been meaning to 3D print some support frames for them 17-Apr-20 02:54 PM not sure how the quality compares 17-Apr-20 02:54 PM probably not quite as good 17-Apr-20 02:55 PM It doesn't make for huge optical path? That's always one of the downside of schlieren 18-Apr-20 01:42 PM Question: do UV shortpass filters exist with cutoffs of 230nm or below? 18-Apr-20 01:45 PM @niflheim these ok? https://www.esourceoptics.com/vuvfilters.html 18-Apr-20 01:48 PM actually yes, the ones at the very bottom are right around what would be optimal 18-Apr-20 01:48 PM more costly than expected, but this confirms existence-- apparently I just needed to search vacuum UV instead of UV-C 18-Apr-20 01:48 PM I think with such high energy photons it gets hard 18-Apr-20 01:48 PM oh yeah vuv is what people call it 18-Apr-20 01:49 PM of course it does; at some point the materials themselves can be used as effective longpass filters 18-Apr-20 01:49 PM yeah this helps a lot -- much appreciated 18-Apr-20 01:49 PM @Mezmorizor is a bit of an expert in this I believe 18-Apr-20 01:57 PM My design personally just abuses the fact that the index of refraction ramps up HARD in the VUV range to reject the light we don't need, but I guess my first three questions would be, A, what's the actual wavelength/wavelength range in question, B, what's the actual use case, and C, how much attenuation is acceptable. 18-Apr-20 01:57 PM But yeah, I'm in the process of building a ~9.9 eV light source so I know a bit about VUV challenges with optics 18-Apr-20 01:57 PM Also this website is your friend 18-Apr-20 01:57 PM https://refractiveindex.info/ 18-Apr-20 03:25 PM interesting 18-Apr-20 03:25 PM I already found a 228nm bandpass filter on eBay for $20 and bought it -- it will work for what I want to do (filter a somewhat-overpowered deuterium lamp to make a far-UV-C germicidal lamp): https://orm.uottawa.ca/my-safety/em-radiation/uv/exposure-limits https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5552051/ 18-Apr-20 03:25 PM ideally a shortpass filter around that wavelength would have been better, but this will do 18-Apr-20 03:31 PM so you're trying to make it safer while minimally making it less useful for cleaning? 18-Apr-20 03:42 PM trying to make something suitable for disinfecting an entryway, yes 18-Apr-20 03:42 PM Ushio isn't selling their Care222 lamps to end-users and refused my request to purchase technical samples as I was not already a registered OEM partner, and I can't find any already-existing KrCl* or KrBr* excimer lamps, so I thought I may as well try this instead 18-Apr-20 03:42 PM https://www.ncbi.nlm.nih.gov/pubmed/30947566 18-Apr-20 03:44 PM Those ionizers work well for disinfecting too 18-Apr-20 03:44 PM Used one in my car years ago after some milk spilled and obviously the carpet couldn't be fully cleaned 18-Apr-20 03:44 PM https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4477231/ interesting 18-Apr-20 03:44 PM I've used ozone to clean spaces before, but it's horribly toxic and takes a couple hours to dissipate. 18-Apr-20 04:14 PM @Mezmorizor are you using fluoride optics, or is that an unobstructed source? is it gas-ionization-based, or something else? 18-Apr-20 04:30 PM I’ve been toying with something similar recently. Trying to work out if you can rig up a respirator that uses UV light for air disinfection 18-Apr-20 04:37 PM Annoyingly the issue seems to be figuring out how to drive a fluorescent tube from a 12V supply 18-Apr-20 07:09 PM That filter is easiest option for what you're doing for sure, yeah. Especially when you found a cheap one. My design in a nutshell is a heated mercury tube filled with low pressures of buffer gas to keep the optics clean (going to try ultrapure argon first due to cost, but helium has better conversion. Ultrapure is important because the common gas impurities all absorb at my desired wavelength). You then shine the fundamental+frequency doubled output of a ~625.7 nm dye laser output onto a parabolic mirror that is focused into the heated mercury cell where it undergoes a 4 wave mixing process to upconvert the light to 9.9 eV (you get a resonant enhancement because 312.85 nm corresponds to a 2 photon electronic absorption in mercury). It's a collinear conversion so the light pulses are all bunched together at this point, and to isolate them I pass it through a MgF2 lens of the proper focal length that's on a translation stage so I can control the a little bit. The visible and UV gets focused at Narnia because the index of refraction change is so extreme at 9.9 eV, and the residual visible+UV won't be an issue for the actual experiment so I don't bother cleaning it up further. All of this is coupled to a high vacuum chamber starting with the mercury cell. In the end you get ~5 kW peak power pulses of the VUV. The big benefit being that you only need one dye laser to get to the VUV. There are similar schemes in the literature with multiple dye lasers that get better efficiency/don't require focusing into the mercury, but the set up is massive as is/we don't have extra lasers. 18-Apr-20 07:09 PM So I guess in less words, yes, MgF2 optic. Nonlinear conversion in mercury pumped by a single laser. 18-Apr-20 11:38 PM @niflheim when i used the ionizer in my car, I'd just hold my breath as i got into it, start it up and roll down my windows immediately and drive away with fan on full... Ozone was all gone by the time i needed to breathe again ( so like 5 or 10 seconds of driving) 19-Apr-20 07:32 AM @Addison-110m My understanding is that when you have enough UV-C intensity to kill viruses in the airflow, you start getting ozone generation and that's Bad for aor that's supposed to be breathed. 19-Apr-20 11:01 AM any concerns with laser cutting a diffraction grating? (45W CO2 laser), would the laser just scatter? 19-Apr-20 11:05 AM 99% of the grating is just bk7 isn't it? 19-Apr-20 11:05 AM I'm really not sn optics guy, but isn't a co2 made diffraction grating limited to <100 lines per mm? 19-Apr-20 11:05 AM ...oh 19-Apr-20 11:05 AM wait 19-Apr-20 11:05 AM is he trying to make a grating 19-Apr-20 11:05 AM or cut an already-existing grating 19-Apr-20 11:06 AM you want to cut the material with the grating on it or do you want to make a grating 19-Apr-20 01:09 PM @rfs That's definitely a concern at the ~220 nm range, but at the same time, ozone has a ~ppb detection threshold, so it should be obvious if that's happening. Just don't be dumb and keep it on despite the smell 19-Apr-20 01:09 PM i want to do both this question is around cutting the grating 19-Apr-20 01:09 PM i have existing grating that i'd like to cut precise shapes from 19-Apr-20 01:09 PM cnc did not leave a good finish on edge, granted i could try some diff endmills 19-Apr-20 01:14 PM diamond saw 19-Apr-20 01:19 PM pretty crazy that drag knives are ~$250 (Which i could outfit to CNC), where an entry level vinyl cutter is < $200 19-Apr-20 01:19 PM Yeah i also say diamond mill bit 19-Apr-20 01:19 PM I got some from Amazon a while back, hoping to grind out a snapped off "easy out" in part of my motorcycle, but the diamonds just ripped off pretty much immediately 19-Apr-20 01:19 PM (and I used it submerged in water) 19-Apr-20 01:21 PM Can you put up a picture or information on what you are cutting ? 19-Apr-20 01:22 PM But the easy out is hardened steel, so your grating presumably would be a piece of cake 19-Apr-20 01:22 PM Diamond mills are not for regular metals typically. They are for other super hard things like ceramic. 19-Apr-20 01:24 PM Well according to internet the only way to remove hardened steel is diamond grinding 19-Apr-20 01:24 PM So either I misinterpreted, or bought cheapo stuff 19-Apr-20 01:24 PM Yeah an easy out or a tap qualifies. Crazy hard stuff 19-Apr-20 01:24 PM The preferred method if you can get the item on a table is actually a wire EDM 19-Apr-20 01:25 PM @samy what do you need the drag knife for? those are pretty easy to DIY from what i have heard 19-Apr-20 01:25 PM Hehe 19-Apr-20 01:28 PM As for the grating you said it’s stainless? What kind of thickness and how open is it? Is it like an expanded grate or a photo etched or punched? 19-Apr-20 01:30 PM @LRM yeah i'll likely DIY it - just surprised they're so expensive. i imagine there's a reason? 19-Apr-20 01:30 PM @nmz787 cool i will try that. apparently diamond bit is how ruling engines make gratings so will try that 19-Apr-20 01:32 PM What type of things do you want to cut with the drag knife? 19-Apr-20 01:32 PM not sure why the tools themselves are so expensive but a friend of mine made his own that just uses the blade inserts from those cricut machines...they are like $9 and last a pretty long time 19-Apr-20 01:32 PM and are we talking about a diamond drag engraver for the gratings...or a drag knife for cutting vinyl and such? 19-Apr-20 01:34 PM Most of the ones I have seen are basically holders for Stanley blades. You can make that yourself for about an afternoons worth of work if you already have the CBC 19-Apr-20 01:34 PM You could also mount a diamond dressing stone in a tool holder and indicate off the tip. 19-Apr-20 01:34 PM All is this stuff is so specific to the item being cut though. 19-Apr-20 01:36 PM item and material in some cases 19-Apr-20 01:36 PM There are also spring loaded diamond scribes that cut pretty good too for this soft things. 19-Apr-20 01:36 PM @nmz787 these the type of things? https://www.amazon.com/Gemstones-Lapidary-Necklaces-Bracelets-Porcelain/dp/B00AZMRZ4W/ref=sr_1_11?dchild=1&keywords=diamond+bit+drill&qid=1587328591&sr=8-11 19-Apr-20 01:38 PM This are good for virtuous things. Not metals. I have a set I use for ceramics but those cheap ones are only good for a few holes or you have to keep track of how deep you plunge them to go just a bit more for each hole cause they wear fast 19-Apr-20 01:38 PM @Charles two things i'm trying to do, one is to just cut plastic diffraction grating sheet accurately. the other thing is trying to produce a diffraction grating in another surface such as metal/plastic to use as a mold 19-Apr-20 01:40 PM Sounds good. Simple question. Laser?? 19-Apr-20 01:40 PM @LRM thinking drag knife for cutting vinyl/viton sheet/etc, i'm also interested in the diamond drag engraver for producing a grating 19-Apr-20 01:40 PM Oh boron 19-Apr-20 01:40 PM Viton 19-Apr-20 01:41 PM @Charles i made some attempts with CO2 laser but people have shared that might not be the right type and i probably need something with smaller wavelength 19-Apr-20 01:41 PM ahhh now it all makes sense, was concerned the two were getting confused 19-Apr-20 01:42 PM CO2 is fine but a fiber type laser would be best. Most consistent. Unfortunately that means contracting it out 19-Apr-20 01:42 PM Unless you have a fiber laser hiding in a warehouse somewhere. Hahahaa 19-Apr-20 01:44 PM i wish 19-Apr-20 01:44 PM Actually I need to do some cutting on the K40 later on. Need to make some mica spacers. 19-Apr-20 01:44 PM do i perhaps need to focus the CO2 laser further? 19-Apr-20 01:45 PM I’m not the expert of these little machines. I know just enough to work mine. There are some people here with far more experience with them and know all the tricks. 19-Apr-20 02:05 PM @samy yeah that's what I bought 19-Apr-20 02:05 PM ahh cool 19-Apr-20 02:05 PM @Charles what do you mean "virtuous things not metals"? 19-Apr-20 02:05 PM It seemed like you said hardened steel was a reasonable substrate 19-Apr-20 02:05 PM If diamond tools are overkill, that seems fine... But I can't understand what you're saying 19-Apr-20 02:26 PM The low cost ones such as in the amazon listing do not have a good bonding on the diamonds. It’s really just a diamond chip paint that’s sintered on. High quality diamond bits are made in a somewhat different way. 19-Apr-20 02:26 PM If you just take one of those and drill Into a piece of 1018 steel it will go dull very quickly. 19-Apr-20 02:30 PM Can you recommend a good one? 19-Apr-20 02:30 PM My motorcycle problem is on the end of the frame, it would be a lot of work to prep to try EDM on it, and I think it would be a lot more complex than me grinding it out 19-Apr-20 02:30 PM My other alternative idea is the grind the welds of the nut that is welded onto the tube and reweld a new one on (this nut had the sheared bolt with a sheared easyout inside) 19-Apr-20 02:34 PM depends how large the part is and where you have the broken bolt/easy out for what will make the most sense 19-Apr-20 02:34 PM sometimes going slowly with a carbide endmill works on broken bolts or even drill bits but I have never tried it on an easy out 19-Apr-20 02:34 PM if that fails then edm is usually the only option if you have to preserve the hole and threads 19-Apr-20 05:35 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_9273-E72C7.JPG 19-Apr-20 05:35 PM just got this sodium vapor lamp in the mail for optical flat but it's not turning on i hear a metal clanking inside, is that normal? 19-Apr-20 05:35 PM i don't see anything moving but it also looks like a piece might not be attached, so not sure if that clanking is normal/expected 19-Apr-20 05:43 PM Mine clanked even if ok 19-Apr-20 05:43 PM what kind of ballast are you using? 19-Apr-20 06:01 PM oh, maybe that's why it doesn't work 19-Apr-20 06:01 PM i just thought it needed 240VAC 19-Apr-20 06:01 PM based on the E40 base screw 19-Apr-20 06:02 PM Ain't E40 much larger than the typical E27? 19-Apr-20 06:08 PM yeah, I used a E40->E27 19-Apr-20 06:11 PM Yeah all of mine had a larger than E27 socket 19-Apr-20 06:12 PM that looks like a high pressure sodium lamp? i thought low pressure ones got more use with optical flats... 19-Apr-20 06:14 PM uhoh 19-Apr-20 06:26 PM easy thing to get confused because the low pressure ones are pretty uncommon specialty things these days 19-Apr-20 06:26 PM something like 90% of their light output is one wavelength but the HPS ones are more broad spectrum 19-Apr-20 06:26 PM https://upload.wikimedia.org/wikipedia/commons/3/3f/Low-pressure_sodium_lamp_spectrum.svg 19-Apr-20 06:40 PM ahh, i see - thanks! 19-Apr-20 06:40 PM would this work? https://www.amazon.com/Philips-321521-90-watt-Pressure-Renewed/dp/B07T945315/ref=sr_1_9?dchild=1&keywords=low+pressure+sodium+lamp&qid=1587344838&sr=8-9 19-Apr-20 06:40 PM ughh why is a BY22D base $50 19-Apr-20 06:41 PM we have some you just power with alligator clips 19-Apr-20 06:42 PM the 90W ones are 20 some inches long just FYI 19-Apr-20 06:42 PM think 35W ones get used for flats most often but as long as you have the space not really a problem to have a longer one 19-Apr-20 06:49 PM ok cool, was just looking for the cheapest and that seems to be it on amazon 21-Apr-20 09:36 AM @Addison-110m there are fish-tank UV sanitizers from China that run on 12V or 24V DC into the inverter that drives the bulb 21-Apr-20 09:36 AM I discovered this at one point by accidentally plugging one into 220V AC, causing the first stage of the converter to violently explode. After that, I powered that one from DC supplies. 21-Apr-20 09:36 AM For drilling into hardened steel, the two most practical choices for drill bits are probably cobalt steel and solid carbide. The latter is harder but shatters more easily. 21-Apr-20 09:36 AM I still haven't built that fiber laser yet. Finding neodymium doped active fiber is difficult. 21-Apr-20 09:36 AM Want to make a fiber disk laser using the 1.6kW worth of 808nm diodes I picked up surplus a year or so ago. 21-Apr-20 09:36 AM Basically just bouncing the 808nm back and forth through the windings of coils of Nd-doped fiber in a gold-plated ring chamber 21-Apr-20 09:36 AM in retrospect, it would have been easier if I had found some that worked on Er-doped fiber instead, but Coherent doesn't seem to sell nearly as many of that kind and they are usually lower powered iirc 21-Apr-20 09:36 AM these ones were obviously intended more for Nd:YAG DPSS 21-Apr-20 09:36 AM still, light is light. just stuck waiting for that one part to show up for sale. if anyone knows where to find Nd-doped silica fiber, ideally at least a couple hundred micron diameter (multimode obviously), I would be most curious. not really looking for cladding-pumped. 21-Apr-20 09:36 AM almost everything I have seen Nd-doped is single-mode or narrow multi-mode. much lower cross-section for conversion efficiency, even given the high reflectivity of gold plating at 808nm. 21-Apr-20 09:36 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/400px-Image-Metal-reflectance-F4413.png 21-Apr-20 09:36 AM cladding pumping requires much better quality pump diode optics 21-Apr-20 09:36 AM https://en.wikipedia.org/wiki/Double-clad_fiber 21-Apr-20 09:36 AM vs https://en.wikipedia.org/wiki/Fiber_disk_laser 22-Apr-20 04:30 PM @Mason_Yu Did you finish the laser simulation? I just set up the rate equations for a 4-level laser and it seems pretty consistent 22-Apr-20 04:32 PM I've not had the time to do any serious coding in the past couple of weeks, and I think I can pretty much calculate what I need by hand 22-Apr-20 04:32 PM What do you mean by pretty consistent? Consistent with what you would expect? And what Einstein coefficients did you use for your system? 22-Apr-20 04:38 PM It doesn't do anything spectrally. Thresholds and outputs for yag/tisaph/ruby are close enough. Coefficients are just derived from state lifetimes, and only the lasing state one really matters so long as the others are fast enough 22-Apr-20 04:51 PM Can you simulate a q-switched laser with it? 22-Apr-20 04:51 PM And when you say it doesn't do anything spectrally, do you mean it doesn't take into account the pumping light wavelength? So you just have essentially a set rate that pumps atoms into the excited state that proportional to pumping power? 22-Apr-20 04:55 PM It uses pump and lasing state wavelength because the rate equations are in terms of populations (and thus # of photons), so the energy of each photon matters, and rather than using tabulated emission cross sections I calculate it from the bandwidth of the gain medium but that's not really any "better." 22-Apr-20 04:55 PM What I meant is that there's no accounting for dispersion / gain narrowing / frequency pulling within the cavity 22-Apr-20 04:55 PM Q-switching in this model would just be making the threshold gain time-dependent. (I went off Milonni + Eberly "Lasers" from 1988). 22-Apr-20 04:58 PM Ah, any chance you'd be willing to share this? 22-Apr-20 05:00 PM Sure, I'm a great practitioner of poor coding practices so be warned. Will just send it to you directly for now 22-Apr-20 05:01 PM Thanks! This will be very educational for me! 22-Apr-20 07:02 PM @idmb oh come on, quit tantalizing us with your private code 22-Apr-20 07:41 PM it's not even code it's just defining variables in and then numerically solving some generic coupled ODEs 22-Apr-20 07:52 PM That sounds like... code 22-Apr-20 08:09 PM Garbage in -> garbage out 22-Apr-20 08:09 PM When I’m done playing around with it I guess I can put it on #resources 22-Apr-20 08:09 PM Just need to heavily clarify what it’s assuming 25-Apr-20 01:20 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/admanpcrthires-DBFCA.png 25-Apr-20 01:20 PM in use in over 1000 labs world wide, prices start at 15k... DAMN 25-Apr-20 02:32 PM dem lazer forgs tho I had a good time talking to them at Photonics west 2019. 27-Apr-20 11:59 AM "Finding neodymium doped active fiber is difficult." - I have some at work. Due to low pump absorption it gets extremely expensive (~50x compared to Yb-fiber lasers of comparable power). If one wants thick multimode single-clad - you'd have to do it DIY, or ready to pay for 100% custom run. 27-Apr-20 03:14 PM I see. I have nowhere near the level of equipment needed to produce optical fiber currently. So I may need to just settle for radial pumping of a Nd:YAG bar, given that these diodes run at 808nm. My reading is that 808nm is only suitable for Nd pumping at any kind of reasonable efficiency. 27-Apr-20 03:14 PM Yb seems to pump best at about 976nm. 27-Apr-20 03:14 PM Er has a rather small peak that oddly coincides with 808nm, but looks better at about 976nm as well. 27-Apr-20 03:14 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Absorption-spectra-of-the-erbium-doped-fib-2F7D6.png 27-Apr-20 03:14 PM Yb also works at ~910-915nm I think. 27-Apr-20 03:14 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/The-absorption-and-emission-spectra-of-the-26186.png 27-Apr-20 03:22 PM what are you trying to make? 27-Apr-20 03:23 PM Oh it was more checking feasibility. Basically I have 20x 80W 808nm diode bars that I obtained cheaply as surplus. Wanted to ideally make a fiber laser, if possible (preferably a fiber-disk laser, tangential pumping of coiled active fiber in a water cooled ring). But may need to settle for a YAG bar. 27-Apr-20 03:24 PM what do you want to do with said laser? 27-Apr-20 03:24 PM The PSU design isn't too bad, but I'm having some difficulty determining whether a fiber laser is feasible. I would really like to have the output coupled to fiber optics for metal cutting and similar. 27-Apr-20 03:24 PM burn stuff, or burn something specific? 27-Apr-20 03:25 PM Surface rust/paint/coating vaporization is also of interest when appropriately focused into a line. 27-Apr-20 03:27 PM so the boring answer is you can probably sell them then buy an appropriate laser from china for cheaper than making them into one 27-Apr-20 03:28 PM The last time I saw something capable of doing this it cost $100,000 27-Apr-20 03:28 PM @ZeptoBars definitely seeing much more use of Yb doped media. Thanks much for the background. 27-Apr-20 03:33 PM what kind of power are you expecting? a few 10s of watts q-switched should be a few thousand 27-Apr-20 03:44 PM specifically - the 100k lasers are going to either be insanely intense flashlamped low-rep-rate ones, or extreme beam quality DPSS ones, or some ridiculous manufacturing laser I've never heard of 27-Apr-20 03:54 PM 10W will not cut metal, aside from very thin sheets. 27-Apr-20 04:00 PM 10s of W, like 30-60W 27-Apr-20 04:00 PM anyways are you trying to make a many-kw fiber laser ? that's why that was my second question 27-Apr-20 04:08 PM Not many, no. 27-Apr-20 04:08 PM push the limit of using every single diode you have? 27-Apr-20 04:08 PM I'm not sure why you are asking. It's a bit unrelated to the original question. 27-Apr-20 04:09 PM x-y problem 27-Apr-20 04:10 PM My reading currently is that Nd:YAG is likely the best option available at 808nm. Coupling it to fiber afterward is likely to be impractical, meaning mirrors or a relatively large gantry assembly. Not ideal. Will need to think more about form factor. 27-Apr-20 04:10 PM I already stated the goal was to determine the best use for the diodes. 28-Apr-20 11:30 AM @niflheim Your best bet is indeed ether Nd:YAG or Nd:Glass lasers based on the cost of rods end "ease" of achieving lasing. Nd:Glass is definitely cheaper at large sizes. Lots of Nd:Glass rods available in Russia from Soviet times, but it is harder to lase in CW... But with Nd:Glass you don't need to tune water temperature/bin diodes to maximum absorption/efficiency. Alternative solution could be multi-stage laser/amplifier, with smaller diameter rods. For example, you can take regular 3mm Nd:YAG rods, cut & poligh to short pieces matching length of pump diode, and assemble ~6 stages this way. Or first stage could be master oscillator, and then 5 amplification stages. While mechanically more complex, it will be much more efficient and easier to run in CW. At such powers Nd:YAG rod cooling is major concern. You probably should target for ~0.8kW cooling for Nd:YAG rod, and ~2.4kW cooling for diode bars at constant temperature not higher than 25°C (i.e. chiller would be required). Thermal management is the largest issue for most of laser designs with power exceeding 100mW ) 28-Apr-20 11:30 AM Even in well designed Nd:YAG lasers with mere 300W of optical pump power, I have seen rods explode into tiny pieces due to thermal stress and tiny imperfections ) So one should not underestimate complexity of this project... Probably a good idea to start with smaller laser using 2x80W pump ahd small rod, and later use it as master oscillator for amplification stage. 28-Apr-20 02:20 PM Interesting. I hadn't thought of using an amplifier. The designs I had seen previously merely radially pumped the same large YAG rod within a DI-water-cooled gold-plated copper chamber. 28-Apr-20 02:21 PM Oscillator + amp is very common for solid state lasers. Ruby, yag, tisaph... 28-Apr-20 02:21 PM There are a lot of different reasons to do it, though 28-Apr-20 02:23 PM Thank you again-- this is very helpful. My main remaining concern, apart from determining how to optimize the configuration of the amplification stages and achieve sufficiently close alignment, would be directing the output beam. I want to be able to use it for cutting metal, vacuum laser welding, etc. I was hoping for a fiber laser because that would have been simpler. Is there any way to couple ~600-1000W @ 1064nm into fiber after lasing within the crystal, or is that impractical at this power level? The couplers I have seen are usually only rated to a couple hundred watts. 28-Apr-20 02:23 PM Hmm yes ruby laser designs I had seen previously, again, were just a single stage-- a few kJ into a large flashlamp, in an elliptical cross section reflective chamber, with one focus of the ellipse coinciding with the flash lamp and the other with the crystal 28-Apr-20 02:23 PM So I need to become more familiar with the design of amplified laser systems. 28-Apr-20 02:23 PM Also yes I had already assumed at least 3kW input power, and hence at least 3kW cooling capacity. I have designed and built water cooling systems up to 20kW so this isn't very difficult. 28-Apr-20 02:23 PM Actually the average car radiator+fan assembly is good for about 30kW at reasonable temperature gradients, limited mainly by the pump 28-Apr-20 02:39 PM Hmm. On the bright side, supposedly passive Q-switching tends to be simpler and more efficient for bulk media than fiber lasers. I have a mid-sized Cr:YAG crystal for that as well. 28-Apr-20 02:39 PM 0.5-1.0 GW/cm³ damage threshold supposedly 28-Apr-20 02:49 PM Then again, might be better to save that for a flash lamp pumped version. Peak power level would likely be unsuited to welding or cutting. Whereas 200-800W CW is perfect for that use case. 28-Apr-20 02:49 PM I already have a spare Nd:YAG rod too small for this application and a number of surplus flash lamps. Probably a better use for the Cr:YAG crystal. https://www.ebindustries.com/cw-and-pulsed-laser-welding/ 29-Apr-20 10:48 AM Oh hey, my paper is on the homepage of Review of Scientific Instruments: https://aip.scitation.org/journal/rsi 29-Apr-20 11:13 AM ( the centrifuge one - https://aip.scitation.org/doi/10.1063/1.5140358) 29-Apr-20 11:20 AM Congrats! It's pretty readable at first but I got lost pretty quick 29-Apr-20 11:31 AM So how do you calculate the polarizability anisotropy for enantiomers? 29-Apr-20 11:31 AM Can you trap any molecule in the centrifuge given low enough temperature and high enough field strength? 29-Apr-20 11:31 AM And if so, can you trap super big and super long macromolecules? Or would the inertia be too great? 29-Apr-20 11:36 AM You offload those calculations to theoretical quantum chemistry groups 29-Apr-20 11:36 AM Naive assumptions differ from tabulated experimental results by hugely varying amounts. 29-Apr-20 11:38 AM This is definitely not for me 29-Apr-20 11:38 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-6EA57.png 29-Apr-20 11:38 AM Also that's a pretty intense laser you've got there 29-Apr-20 11:39 AM Ionization is extremely limiting, and ease of ionization tends to scale with molecular size/complexity, so instead of increasing intensity you stretch the pulse more and maintain intensity (which requires adding energy) 29-Apr-20 11:39 AM So 5*10^12 is pretty much the absolute limit then? Also I thought you mentioned people were spinning molecular ions? 29-Apr-20 11:41 AM Yeah so for those calculations we take XYZ moment of inertia tensors and XYZ polarizability tensors from literature or friends. I didn’t do the simulations myself, just helped set them up 29-Apr-20 11:41 AM And that’s the limit ish for molecules discussed, others limit much earlier. 29-Apr-20 11:41 AM Ions are okay (because these dynamics are way faster than the time of flight speeds) but by ionize I really mean fragment due to ionization 29-Apr-20 11:44 AM Ah okay. So the molecules are not just a low density gas in your chamber? There's time of flight involved? 29-Apr-20 11:45 AM Guess I'm adding stuff not necessary - we do both time of flight of molecular gas jets and raman spectroscopy of gas in a chamber 29-Apr-20 11:45 AM the data in the paper is low density gas in a chamber 29-Apr-20 11:46 AM Gotcha 29-Apr-20 11:46 AM the people spinning ions were doing it with a jet in a time of flight 29-Apr-20 11:46 AM PI loves discussing "limits," in this case the centrifuge limits are based on what you can buy as standard systems 29-Apr-20 11:46 AM ~300k femto amplifiers 29-Apr-20 11:46 AM for another ~200k you could double the limit (whereas the two centrifuges compared were going by a factor of 20) 29-Apr-20 11:48 AM Luckily you only need one lol, when you mentioned in the intro that you have to interfere two circularly polarized pulses together I thought wow they've got two 29-Apr-20 11:48 AM if you drop your repetition rate from 1khz to 10hz and add another 400k amplifier you can add another factor of 10 29-Apr-20 11:48 AM we have two three, actually 29-Apr-20 11:49 AM ~2007 spectra physics spitfire, ~2011 Coherent Legend, 2019 spitfire 29-Apr-20 11:49 AM the 2007 spitfire's pump laser started to get unreliable so we repurposed the oscillator from it to get a discount on the 2019 spitfire 29-Apr-20 11:49 AM and we actually have the 400k amplifier to get the factor of 10 29-Apr-20 11:49 AM but to get the factor of ten would require changing the beam path length from around 6m to around 30m 29-Apr-20 11:49 AM and when you're trying to have to pulses overlapped... uh, no thanks. Not to mention the repetition rate hit 29-Apr-20 11:53 AM So by factor here you mean the spinnability factor right? And why the need for longer beam path? high beta = high rep rate = short path? 29-Apr-20 11:55 AM High beta = fast acceleation = requires more force = requires more intensity, just like newtonian stuff 29-Apr-20 11:55 AM fin figure 3, what gets done to stretch the pulse further is the grating offset from lens focal length increases 29-Apr-20 11:55 AM since one grating moves towards a lens, that then requires a longer focal length lens 29-Apr-20 11:55 AM which then just makes that ridicuoulsly long. we're already at 50cm so 2m long path on table (which gets reversed after the retro -> 4m path in centrifuge shaper) and then there's space for combining the beams 29-Apr-20 11:55 AM you also have to go to larger optics to maintain numerical aperture and thus final frequency 29-Apr-20 11:55 AM 4" optics ew 29-Apr-20 11:59 AM Ahh, what happens if you run at a higher temperature? So you increase the fraction of spinning molecules even with a low factor? 29-Apr-20 11:59 AM The laser + centrifuge entirely occupy a 10'x4' table as-is 29-Apr-20 11:59 AM temperature just goes down the stat mech rabbit hole 29-Apr-20 11:59 AM where you're always likely to have some molecules that can be caught in the centrifuge and spun 29-Apr-20 12:01 PM Seems like an interesting optimization problem 29-Apr-20 12:02 PM I don't think we've done any simulations above 300k 29-Apr-20 12:02 PM in figure 2b, we like being in the sigma>2 regime 29-Apr-20 12:02 PM at which point lower temperature is always better 29-Apr-20 12:02 PM it's only when your centrifuge can't properly spin the molecule from ground state that higher temperature can ever be better 29-Apr-20 12:02 PM also my main intent with this tool is helium droplets where it's 0.4k, so.... 29-Apr-20 12:08 PM Helium does not go through Bose-Einstein condensation at that temp right? 29-Apr-20 12:10 PM I think it is one 29-Apr-20 12:10 PM https://phys.org/news/2013-10-limit-superfluid-helium-nano-highway.html 29-Apr-20 12:12 PM Why do you want to spin helium? It's symmetric no? 29-Apr-20 12:13 PM want to spin stuff in helium 29-Apr-20 12:13 PM https://www.nature.com/articles/s41467-018-07995-0 29-Apr-20 12:13 PM the centrifuge is the most controlled way of studying highly excited dynamics 29-Apr-20 12:18 PM I've skimmed through half of it and still don't understand why liquid helium helps. Not great news because liquid helium was a class topic just two weeks ago 29-Apr-20 12:18 PM Not good news for my statistical mechanics final neither 29-Apr-20 12:19 PM Oh it's not that it helps 29-Apr-20 12:19 PM it actually makes things really hard and annoying 29-Apr-20 12:19 PM buffer gas cooling? 29-Apr-20 12:19 PM it reduces signal by orders of magnitude, and makes the molecules more difficult to spin 29-Apr-20 12:19 PM I like how they say slow laser pulse is in 100 ps lol, I guess if you are used to femptosecond it's slow 29-Apr-20 12:20 PM it's more than buffer gas cooling, we are interesting in the interactions between helium and molecule 29-Apr-20 12:20 PM we do do buffer gas cooling stuff too, the PPO orientation stuff was mixing like 0.1bar PPO with 20bar helium 29-Apr-20 12:23 PM I didn't know you could have a rotational temperature for helium 29-Apr-20 12:23 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-EDFD8.png 29-Apr-20 12:23 PM I thought you needed quantized rotational energy levels, and helium shouldn't have that, being symmetric and all 29-Apr-20 12:23 PM So it must be diatomic at least 29-Apr-20 12:25 PM Yeah 29-Apr-20 12:25 PM I said we want to spin stuff in helium, maybe missed it because of the link 29-Apr-20 12:25 PM but also there are helium dimers (diatomics) 29-Apr-20 12:26 PM The nature paper explicitly reference this 29-Apr-20 12:26 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-EA437.png 29-Apr-20 12:26 PM I guess it must be that dimers form in helium droplets 29-Apr-20 12:26 PM that's saying molecules in helium droplets have rotational temperature 0.4k 29-Apr-20 12:27 PM Oh facepalm moment, I thought it meant molecules of helium ‍♂️ 29-Apr-20 12:27 PM with a big enough droplet, no matter what you put in it it gets cooled down to 0.4k in all resepects, afaik 29-Apr-20 12:27 PM and the droplet shrinks by "boiling off helium" to compensate 29-Apr-20 12:29 PM This indicates to me that it's time to venture out to the grocery store to replenish my coffee supply. Wish me luck! 29-Apr-20 01:20 PM What to do with an old HeNe inside a broken/incomplete FTIR I've had for a decade? 29-Apr-20 01:20 PM I don't really want the FTIR taking up space anymore 29-Apr-20 01:20 PM Even though it does seem like a good museum/take-apart piece for my kid in 8 or 10 years 01-May-20 03:19 PM I just got asked a researcher question about calculating the MPE for the sclera of the eye with near IR. That is sufficiently weird that I want to know a lot more about the project that spawns this kind of question. I feel there's a story. 01-May-20 03:24 PM could be eye tracking 01-May-20 03:24 PM ... now i'm kinda curious too 01-May-20 04:25 PM Eye tracking experiments I'm very familiar with. Sclera tends not to be the point of interest. If the retina and cornea is safe, the sclera is safe. But if your interest is specifically the sclera...??? 01-May-20 04:53 PM They could reply with "oh we don't plan on aiming it at the pupil or retina" 03-May-20 02:34 PM Man, I need to check here more often, but it's important to note that symmetric molecules (the actual selection rule is lack of a permanent dipole moment, but I assume that's what you meant) don't have a pure rotational spectra. That is distinct from not having quantized rotational levels. They do, and that's why we can do the rovibrational stuff we do on molecules that don't have a permanent dipole moment like the methyl cation. 03-May-20 02:34 PM and when you're trying to have to pulses overlapped... uh, no thanks. Not to mention the repetition rate hit 03-May-20 02:34 PM It's fine just spend an extra 2 years on the PhD 03-May-20 02:35 PM With how unstable liquid-doped helium droplets are 03-May-20 02:35 PM Collection time doesn’t scale linearly with acquisition rate 03-May-20 02:36 PM Okay an extra 4 years 03-May-20 02:44 PM Hey 03-May-20 02:44 PM The longer you’re in school 03-May-20 02:44 PM The more you make from using interest-free student loans in a high interest savings account 03-May-20 02:48 PM True 03-May-20 02:48 PM And that is also kind of making me think, if I remember correctly that selection rule I quoted is derived from a Taylor expansion of the dipole moment surface 03-May-20 02:48 PM So it's not clear to me that it'd even be valid for an optical centrifuge 03-May-20 02:48 PM Also assumes equilibrium geometry iirc which may or may not be fine at such high rotational energy 03-May-20 02:48 PM Guess I'm really saying I imagine it's a large amplitude motion so any traditional theory is going to fail badly 03-May-20 03:00 PM Classical stuff works much better for getting an intuition with the centrifuge 03-May-20 03:00 PM Just assume everything as a dumbbell with moment of inertia from the naive spectroscopic rotational constant someone else came up with 03-May-20 03:00 PM Pretend field carrier oscillations don’t exist and treat induced dipole as permanent dipole 03-May-20 03:02 PM To be perfectly honest most molecular spectroscopy should be thought of classically 03-May-20 03:02 PM The theory that was developed in the 60s is all taking the classical result and quantizing it 03-May-20 03:02 PM And not much changes 03-May-20 03:02 PM Though there is some evidence that our rotational constants don't suck as much as we thought and it was just a lack of computational power/methods that made us think they suck 13-May-20 04:21 PM so what does this look like to everyone? (axis labels in the bottom left should be Ex and Ey, not time and Ex) 13-May-20 04:21 PM is it clear from the increased angular spacing in the top-left that the angle the purple thing in the bottom-left rotates at is speeding up? 13-May-20 04:24 PM it is now that you mention it 14-May-20 05:41 AM yes on mention 14-May-20 05:41 AM not the first thing noticed, but clear when indicated 14-May-20 05:41 AM great use of color though-- very readable 14-May-20 02:09 PM I think I have the speeds and ratio of acceleration to carrier frequency better now 14-May-20 02:09 PM this took 3 hours to render cause I can't code well in matlab 14-May-20 06:46 PM Actually yes that one is much more clear 14-May-20 06:46 PM Lines in the upper right and lower right could be a bit thinner, granted 14-May-20 07:04 PM The bottom right 100% needs to be in there imo. It's not obvious to me that the bottom left's rotation is accelerating based off of that one, but the top left does show it so that's probably fine. 15-May-20 03:43 PM https://physicsworld.com/a/quantum-control-using-laser-light-could-turn-insulators-into-conductors-and-vice-versa/?fbclid=IwAR0tfQuXBgrPLDN1KZ9GHC9AgeFQ6qIcEJKjUx-crGVNkpcqUqmz02FboMA 15-May-20 03:43 PM nifty 16-May-20 12:36 PM any software suggested for seeing how different waves may interfere with each other? at the moment i'm trying to understand how laser light obeys Huygens principle since I'd naively expect it spread into an interference pattern 16-May-20 01:05 PM https://www.nature.com/articles/ncomms2894 16-May-20 03:18 PM @samy audacity?? 16-May-20 03:18 PM I assume it has a waterfall plot like gnuradio 16-May-20 03:32 PM @nmz787 i'd use gnuradio but i'm trying to see this in 2d space - especially diffraction of a combination of frequencies. every explanation (simple enough for me to understand) discusses the interference and shows interferograms/graphs of the interference which explains the constructive/destructive amplitude variations, but i haven't found anything that clearly shows/explains why the frequencies themselves are dispersed 16-May-20 03:32 PM i'm also trying to do a test with audio (IRL) using white noise and many slits near some wavelengths to see if i can similarly hear/view FFT of the diffracted waves as it would be neat to see if the amplitude of certain frequencies is higher at certain points 17-May-20 11:52 AM any tools people like to measure micrometers with optical microscope? do people just use some reference like a slide with micrometers on it, or some other method to know the size of things they're looking at? 17-May-20 12:08 PM there are a few ways to do it...eyepiece scales are a quick easy way at a glance if you know the conversion factors for divisions to micrometers at the objective magnifications (reference slides are handy). you can also take a few photos of a reference slide with the various objectives and then you can convert pixel distances to measurements. 17-May-20 12:08 PM neither one is terribly accurate but for most things they are good enough 17-May-20 01:33 PM ahh cool, thanks! 17-May-20 01:35 PM it's definitely much easier to have a reference overlaid in the same plane as your subject 17-May-20 10:25 PM @samy might google/eBay hemocytometer 17-May-20 10:25 PM Or if one dimension is OK, something like this 17-May-20 10:25 PM https://www.amazon.com/OMAX-0-01mm-Microscope-Calibration-Micrometer/dp/B00FG89F0M/ 17-May-20 10:25 PM Ha, there's a similar item that was linked there for 5 bucks less https://www.amazon.com/gp/aw/d/B078QJHKFX/#aw-udpv3-customer-reviews_feature_div 17-May-20 10:49 PM aahh nice 19-May-20 10:14 AM @funranium do you have one of these? 19-May-20 10:14 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Martin_Slide_Rule-7991A.png 19-May-20 10:53 PM Molten silver chloride does seem to work decently well for sealing optical windows. Uniform heating and pre-tinning the tube itself (get the end of it orange hot and dip it into the AgCl powder) first appear to be helpful. 19-May-20 10:57 PM how important is blaze wavelength/angle for a littrow external cavity resonator? like can i just grab any reflection diffraction grating, or do i need a specific optical grating for each laser? 19-May-20 10:57 PM also, like, with blazed gratings, it seems like e.g. thorlabs only sells a few different blaze wavelengths. do i just pick the closest one (750nm?) if i want to e.g. stabilize 632.8nm? 19-May-20 10:57 PM it seems like there tends to be some tuning wiggle room but idk how much yet 20-May-20 09:23 AM They usually have efficiency curves 20-May-20 09:23 AM Yeah, here’s one: 20-May-20 09:23 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-D310A.gif 20-May-20 09:23 AM If you’re making a cavity, usually you don’t like losses 20-May-20 05:19 PM @idmb OMG NO I DO NOT 20-May-20 05:20 PM you should make a modern one 20-May-20 07:58 PM That seems.. kind of low, but I don't know 20-May-20 07:58 PM Could be very limiting for power level given likely cooling difficulties 20-May-20 08:02 PM What seems low? 20-May-20 08:09 PM Efficiency 20-May-20 08:09 PM But again, not my area 20-May-20 08:11 PM That's just a random grating I found on thorlabs but nah, that's pretty typical sadly. My $3000 gold-coated gratings are still only ~88% efficient at best 20-May-20 08:48 PM Where do you usually get your really high quality optics from? Thorlabs or Newport tend to cover 99% of our use cases, but outside of them I really only know CVI 20-May-20 08:58 PM spectrogon are the grating company 20-May-20 08:58 PM other than that it's thorlabs/newport/cvi or "a friend in israel" 20-May-20 09:14 PM What's the grating place in Rochester NY? 20-May-20 09:14 PM "Richardson, a Newport company" 20-May-20 09:14 PM I visited them once when picking up a free donation grating 20-May-20 09:31 PM Fair enough. I doubt I'll ever need gratings anytime soon (unless we don't get rotational resolution when the new instrument is finally up and running), but still good to know. 21-May-20 12:59 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Optical_Post_A1-780-FB4BF.png 21-May-20 12:59 PM TIL we're actually supposed to be doing this, and aren't total barbarians 21-May-20 02:17 PM Is that just for storage of the screwdriver? 21-May-20 02:53 PM Those posts get really stuck if you leave them for a long time 21-May-20 02:53 PM So you use the screwdriver/hex key for leverage 21-May-20 02:53 PM Though I am curious, why did you think they had those holes if it wasn't for that? 21-May-20 02:53 PM Though I do feel like I'm going to destroy the hex key whenever I do it on a stuck one... 21-May-20 03:11 PM I thought they were for leverage, but not by using the drivers 21-May-20 07:11 PM I thought it was a bonus challenge where you "thread the needle" with the beam when nobody else is around 22-May-20 09:32 AM One lab had a collection of bent screwdrivers framed, each tagged with a grad student/postdoc's name and date, and the statement over the art installation "If you ever wonder why we have dozens of all hex drivers sizes EXCEPT 1/16, this is why. Brute strength is rarely the answer with lasers." 22-May-20 10:12 AM I have one that works fine 22-May-20 10:12 AM but there's a full 90 degree twist in it from overtightening 04-Jun-20 09:54 AM Speaking of twists, here's a presentation from the conference that just happened on using twisted light to orient molecules: https://assets.onlineeventapp.com/aps/damop20/EventFiles/apsdamop20/PresentationFiles/Uploads/15337533/25121120/video_presentation_chiral.mp4 presents some stuff I'm involved in 04-Jun-20 11:34 AM https://www.laserpecker.com/ @funranium 04-Jun-20 06:43 PM Long since reported to the FDA, both their original version last year and the PRO version a couple months ago. And the FDA also seriously can't believe they named their product that. 04-Jun-20 08:10 PM I got some new mirrors for the K40. These are silicon. As I understand those are good for these low wattage lasers. Any truth to that? 05-Jun-20 12:21 AM I thought silicon was transparent 05-Jun-20 07:13 AM silicon substrate presumably 05-Jun-20 10:44 AM I like how laser Pecker's new version moved it even closer to UV so it can be even more dangerous. 06-Jun-20 12:29 PM looking at cameras for the toolmaker's microscope, again.. due to low light (or is that dependant on not having a ton of backlight, can I use some high power LEDs to actually get good light? what we want is sharp contrast and a decent resolution) we are looking at larger image sensors, maybe full frame.. the two at the top of my list, for price and the wifi connectivity with an API available is the Sony A7, and the Nikon D610.. any other suggestions to add to the list? trying to stay well under 1k.. smaller sensors could certaily make this easier 06-Jun-20 12:29 PM I was considering the sony qx1 wifi-only to smart phone camera thing, but for not too much more a bigger frame would give better quality - also, the availability seems much less 06-Jun-20 12:29 PM APS-C may be plenty for sensor size wise.. I mean, I even captured a decent shot of through the eyepiece with my phone, it comes down to how good I want it, and how much I am willing to spend 06-Jun-20 01:21 PM If anyone wants to chime in and agree that getting a silhouette (and computing sharp contrast, for basically white/black), is not actually "low light" then I can certainly go with the cheaper smaller sensor just fine.. right? 06-Jun-20 03:38 PM I can chime in that an older full frame doesn't actually give you a low light advantage over a much newer / fancier smaller sensor 07-Jun-20 02:00 PM i'd like to try the double slit experiment but potentially with single quantities if possible - eg single electron or photon. suggestions on which would be easier (cheaper) to setup? 07-Jun-20 02:14 PM looking at photomultiplier tubes on ebay that might be good for single photon detection, maybe electron detection would be harder 07-Jun-20 02:16 PM PMTs are good for single photon detection 07-Jun-20 02:16 PM if you break them open and use the electron multiplier alone they're good for single electron detection 07-Jun-20 04:32 PM ahh 08-Jun-20 09:38 AM break them free 08-Jun-20 12:09 PM Single photon sources are a pain in the butt, so I imagine single electron would be easier. Albeit I'm not sure. 08-Jun-20 12:12 PM not sure about that 08-Jun-20 12:12 PM the only single single electron source I can think of is a single photon source and a photocathode 08-Jun-20 05:45 PM All I'm really saying is that if single electron sources aren't easier than single photon sources, you should probably reconsider doing it. 16-Jun-20 01:12 PM Does anyone know of an optics safe epoxy or glue? It looks like continuum used some blue stuff that looks an awful lot like loctite, but I dont want to commit to that 16-Jun-20 01:14 PM https://www.edmundoptics.com/c/adhesives/644/ 16-Jun-20 01:14 PM You mean like... the optical cement they use for making beamsplitters...? 16-Jun-20 01:14 PM https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=196 16-Jun-20 01:17 PM I think Norland makes some 16-Jun-20 01:18 PM Honestly, I dont know. All I know is that the qwp has a circular housing, and they clearly used some sort of glue to get it in the housing in the first place. So I guess I'm looking for quartz-plastic glue of some sort? 16-Jun-20 01:18 PM Though it might be a polymer waveplate. Maybe I can convince customer service to tell me 16-Jun-20 01:18 PM https://www.norlandprod.com/adhesiveindex2.html#noa 16-Jun-20 01:19 PM Those look promising, thanks 16-Jun-20 01:20 PM norland is the go-to afaik 16-Jun-20 01:20 PM One of those days where everything breaks :( 19-Jun-20 01:35 PM Aligning non alignable optics was fun :) 19-Jun-20 01:35 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200619_010402-D7476.jpg 19-Jun-20 01:37 PM everything is alignable if you have a hammer big enough 19-Jun-20 01:37 PM looks nice, laser show projector? 19-Jun-20 03:10 PM alignment was basically bending the frame and a hammer for the fine adjustments 19-Jun-20 03:10 PM Yeah, a 100€ RGB galvo projector. Was supposed to have ILDA but listing was wrong 19-Jun-20 03:10 PM Will need to hack ILDA in when I get my Laser audio DAC 22-Jun-20 09:43 AM Does anyone know how to get the quarter wave plate rotation correct in a pockels cell q-switch in a laser that doesnt have a "have pockels cell on for entire flashlamp discharge" setting? My only idea is checking pulse lifetime on a scope, but I'm not sure if we have the photodiode for that on hand. 22-Jun-20 09:43 AM And I gotta say, the lack of a long pulse mode is killing me 22-Jun-20 09:59 AM Does anyone here have experience measuring thin films? I made an aluminum deposition on a microscope slide, and I'm trying to find a way to see just how thick it is. I tried building an ellipsometer, but I don't think my webcam spectrometer has the resolution to measure the interference. I'm wondering if there are any other good DIY methods that people have had luck with. Thanks! 22-Jun-20 10:10 AM @Mezmorizor correct for what? maximum energy? shortest pulse? 22-Jun-20 10:10 AM Or just waveplate vs pockels cell orientation?... 22-Jun-20 10:29 AM Shortest pulse would be the idea, but I realized the easiest way is to just check power after doubling because that's sensitive to peak power unlike the straight output 22-Jun-20 10:29 AM Though I'll also find a photodiode to characterize the pulse at some point 22-Jun-20 01:02 PM yeah I was gonna say - just measure the parameter you care about and optimize that lol 22-Jun-20 01:02 PM I love XFROG 22-Jun-20 01:02 PM beautiful technique 22-Jun-20 01:05 PM Well, the problem with that is that I dont JUST care about the second harmonic. I'm also using the fundamental, but a proper q switch doesnt actually change the average power which makes things hard 22-Jun-20 01:05 PM Though in this case I'm pretty sure second harmonic corresponds to short pulse which corresponds to proper polarization 22-Jun-20 01:46 PM Though I guess my real problem is that the parameter I care about is pulse width and 1 ns photodiodes don't grow on trees 22-Jun-20 02:15 PM I would also like to state that I can firmly say that I hate continuum/amplitude 22-Jun-20 02:15 PM What a garbage operator unfriendly design 22-Jun-20 02:20 PM so far I don't dislike anything about coherent 22-Jun-20 02:20 PM but spectra are oof 22-Jun-20 02:22 PM God I wish this continuum was anywhere near as user friendly as a spectra 22-Jun-20 02:22 PM Plus the spectra manuals are gold and can basically replace laser textbooks 22-Jun-20 02:22 PM Meanwhile this one is "lol I won't label all the parts" 22-Jun-20 02:24 PM spectra never gave us a diagram of our $300,000 laser 22-Jun-20 02:24 PM we had to map it out ourselves 22-Jun-20 02:24 PM I guess I'll give them that the laser itself works well. Consistent power output, short pulse, good beam profile, etc. 22-Jun-20 02:24 PM Oof 22-Jun-20 02:24 PM also the chassis dimensions the quote are wrong 22-Jun-20 02:24 PM the laser is bigger than their CAD files claim lol 22-Jun-20 02:24 PM Okay, to be fair I haven't dealt with a spectra laser that is newer than 30 years old 22-Jun-20 02:24 PM Maybe they've gone bad 22-Jun-20 02:25 PM their GUIs are made by laser techs rather than people who can make functional software GUIs 22-Jun-20 02:26 PM I can see that. That's also not something we ever have to deal with because everything is synced up to a delay generator anyway 22-Jun-20 02:26 PM While we personally haven't seen this yet, the lab across the hall also told me that continuum have a tendency to have terrible electronics that break easily 25-Jun-20 04:34 AM Finished designing and laser cutting the parts for my reflected light adapter for my old olympus microscope, havent done the matte/opaque coat yet but it works pretty well 25-Jun-20 04:34 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/EbVN47oXkAg1zYO-FB220.png 25-Jun-20 04:34 AM close up shot of it 25-Jun-20 04:34 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/EbVOW8OWsAE4GSg-5E9BB.png 30-Jun-20 04:24 PM ... also linking this here because it's amusing to me (and not in #swap-meet bc i'm willing to bet some of y'all are already bidding on 'em), but ️ FIVE CRATES OF CAPACITORS ️ https://m.publicsurplus.com/sms/auction/view?auc=2587666 30-Jun-20 04:24 PM i'd love, like.. <10 of those super low inductance Maxwell capacitors, but i don't think anyone would like it if i came home with a uhaul full of the rest of the assorted environmental toxins there 01-Jul-20 01:10 AM wow those are some serious caps 01-Jul-20 12:03 PM saw someone mention those over at the toorcamp slack. had a good laugh about them. 01-Jul-20 12:03 PM wonder what they were used for 01-Jul-20 12:05 PM Some accelerator stuff? My thryratrons were from Jefferson lab and they were running some klystrons 01-Jul-20 12:05 PM These are smaller, but perfect for a pulse forming network 01-Jul-20 02:03 PM that's my guess yeah, real nice inductance figures but not a ton of capacity 01-Jul-20 02:20 PM I’m debating bidding on an early 1970s rubidium clock. 01-Jul-20 02:20 PM I’m curious what could be wrong with it. 01-Jul-20 02:20 PM My understanding is that the physics package is a rubidium lamp in a microwave cavity with a solar cell measuring light output. It’s essentially optics. 01-Jul-20 02:22 PM the cells can break, both by reaching their eol and literally breaking 01-Jul-20 02:23 PM I know used, untested cesium beam clocks are typically garbage, given that they’re heating up a cesium beam that depletes, the ion pump is the tube saturates, and the replacement tubes are unobtainium for any reasonable cost. It’s literally a mass spec in a vacuum tube. 01-Jul-20 02:23 PM By cells, are you talking about the rubidium lamp? 01-Jul-20 02:24 PM the lamp and resonator 01-Jul-20 02:24 PM they're two parts, one just emits light, the other one is irradiated by microwaves 01-Jul-20 02:26 PM Hmm.... how likely are they to break? I guess I’m wondering the chances that this thing might actually work? 01-Jul-20 02:26 PM they're just glass tubes, in normal storage / transport they won't break, but drop them once and they're gone 01-Jul-20 02:26 PM and the lamp has a limited lifetime, but I don't know how long that usually is 01-Jul-20 02:43 PM Hmmm 01-Jul-20 02:43 PM I’ll see how much it sells for 01-Jul-20 02:43 PM It also has a very nice Patek Philippe dial clock on the face. 01-Jul-20 02:43 PM Even if the rubidium is shot, I could probably hack it to make the clock dial work, say, with another rubidium source, or even a simple TXCO. 01-Jul-20 02:45 PM good luck! 01-Jul-20 02:45 PM Thanks!!! 01-Jul-20 02:45 PM you could electrically simulate the rb with an extremly high Q 6.8 GHz Bandpass 01-Jul-20 11:04 PM yes 03-Jul-20 12:40 PM The one smart/wifi enabled sony camera (with interchangeable lenses) I've been looking for to interface w/ toolmaker's microscope popped up on ebay, reeally thinking about it - then the idea is something like a rpi to wifi direct and analyze the photos and database 'em (and also interface with the glass scales), and a tablet to then present and interface as DRO and optical comparator - basically 03-Jul-20 02:33 PM What was the reason for not just hooking a raspi up to an older dSLR? 03-Jul-20 07:31 PM mainly, I can put the entire camera body inside the hole (that the mirror for the projection unit would mount onto).. I dont know if for focusing I would need to be above it - yet, but that's one big reason 07-Jul-20 07:18 AM auction for that camera ends in like 12hrs, likely going with it - even just to see how well it works and so forth, if I want something a bit different or better I'll re-evaluate, but I think it's the best initial trial 07-Jul-20 07:18 AM as I can shove the entire thing into the projection head of the microscope 07-Jul-20 09:26 AM Someone put a GF2 up for $15 CAD here yesterday 07-Jul-20 04:41 PM someone made the seller an offer before the auction ended! ugh, I should have put in the opening bid to have removed that option! such a n00b mistake 07-Jul-20 04:41 PM that was the only one in the US for sale, too.. discontinued item, etc etc .. .may look for something more available 07-Jul-20 04:41 PM and just figure out the lense thing since I wont be able to put the camera body in like I oculd with that one 12-Jul-20 08:43 AM I know nothing about lasers. A friend wants to know what this connector is. People have suggested MHV but the power supply outputs 6kV with 10kV starting voltage. 12-Jul-20 08:45 AM @rdpierce photo didn’t load 12-Jul-20 08:45 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-69C95.jpg 12-Jul-20 08:48 AM Yeah that’s MHV 12-Jul-20 08:48 AM Most voltage ratings are doubled when mated 12-Jul-20 08:48 AM The ratings are largely for live detachment. 12-Jul-20 08:48 AM If you can force a BNC on, it’s definitely MHV 12-Jul-20 08:50 AM That’s interesting. So... if someone tried to disconnect it when live, it’s going to arc like crazy.... 12-Jul-20 08:51 AM No, because safety margins 12-Jul-20 10:44 AM Ok, other people on the mailing list seem to think it’s a KINGS 10 kV or 20 kV series connector. 12-Jul-20 10:44 AM https://www.winconn.com/wp-content/uploads/2015/12/rfcatalog_web.pdf 12-Jul-20 11:19 AM It definitely looks like an MHV 12-Jul-20 01:28 PM According to this it's just BNC: https://www.repairfaq.org/sam/laserhsc.htm#hscsp3 12-Jul-20 01:28 PM Spectra-Physics Model 255 Exciter (SP-255) My only complaint is that the laser head (LT1 and Rb) attaches via a high quality HV BNC connector rather than the more common Alden type. When run at full line voltage, one additional multiplier stage will result in a starting voltage that approaches 18 kV. This should be sufficient for most HeNe tubes. However, more stages may be needed if the supply is to be run at reduced line voltage. See the other HeNe laser power supply schematics for ideas. My only concern would be the insulating rating of the HV connector - I do not know if it is sufficient for this boosted starting voltage. An Alden type connector might in fact be better. 12-Jul-20 01:28 PM tldr laser folks bypass HV ratings all the time 12-Jul-20 06:50 PM oh, that connector 12-Jul-20 06:50 PM it's not SHV, MHV, or BNC 12-Jul-20 06:50 PM it is in fact a Reynolds/Teledyne 167-3555.. thing. it's rated for 15kV http://catalog.teledynereynolds.com/item/all-products/ctors-with-recessed-contacts-for-added-user-safety/167-3555 12-Jul-20 06:50 PM i have one on an ancient PMT base. nothing fits it. replace it and save yourself the misery D: 12-Jul-20 06:50 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/reynoldswack-EE816.jpeg 12-Jul-20 06:50 PM but, also, to the credit of the laser manufacturers, voltage ratings on these things have pretty sizable safety factors in them and i've seen NIM HV PSUs that put 10kV down standard SHV. Also, the starting pulse being a pulse makes flashover somewhat less likely on top of all that 12-Jul-20 06:50 PM oh, that KINGS connector might be compatible too 12-Jul-20 07:47 PM @qualia why do you say it's that other connector? I feel like the laser repair FAQ calling it BNC is probably as reputable as it can get 12-Jul-20 07:47 PM without measuring it or something up close 12-Jul-20 07:47 PM Or rather... Whatever it is, BNC should work with it, if that person says it's BNC... Even if it isn't 12-Jul-20 07:51 PM BNC does mate with the bayonet of that connector, but the center pins don't make contact (just tested) 12-Jul-20 07:52 PM why do you think it's that on the laser then? 12-Jul-20 07:52 PM from the photo it seems very hard to distinguish from MHV or the other connector 12-Jul-20 07:54 PM The insulator aspect ratio gives it away, one sec 12-Jul-20 07:54 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20200712_195558-6E38C.jpg 12-Jul-20 07:54 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20200712_195720-98CCF.jpg 12-Jul-20 07:54 PM pardon the crummy pics, but: that's SHV, MHV, and the weird Reynolds thing. SHV has a wide thin insulator, MHV looks identical to BNC except the HV bit + insulator comes up right to the surface (why?!) and the Reynolds things is a bit thinner (and longer) than both 12-Jul-20 07:54 PM happy to be proven wrong, but i'm about 90% sure on this >_> 12-Jul-20 08:01 PM Looks right to me! Does an MHV cable make contact? 12-Jul-20 08:01 PM i don't even know if i own an MHV cable, lmao 12-Jul-20 08:01 PM I hate these things so much 12-Jul-20 08:01 PM lemme look 12-Jul-20 08:02 PM Why is there no go-to resource for identifying HV plugs? 12-Jul-20 08:02 PM there are just so many 12-Jul-20 08:04 PM multimeter sez no 12-Jul-20 08:06 PM time to wedge a small needle in the socket and try again with that there? 12-Jul-20 08:06 PM yum yum, scraped up BeCu contacts :D 12-Jul-20 08:10 PM well if it's there forever you'll never see the scratches 13-Jul-20 10:06 AM Probably a stupid question, but any ideas how to easily adjust a dichroic at that angle without accidentally burning yourself or reflecting laser light god knows where with a hexbkey? 13-Jul-20 10:06 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20200713_130121-70919.jpg 13-Jul-20 11:40 AM do you have an hex snake things? 13-Jul-20 11:40 AM gooseneck 13-Jul-20 11:40 AM also 13-Jul-20 11:40 AM if you put the mirror in the mount the other way 13-Jul-20 11:40 AM wouldn't the knobs be easy to reach? 13-Jul-20 11:40 AM especially if you have ultima mounts with the big knobs instead of the dinky thorlabs ones 13-Jul-20 12:13 PM That particular mirror is so far off atm that there's no harm in trying the reverse, but I'm pretty sure I run into the same issue except now the reflection is in my hand path rather than the transmission. Dont think I have the hex key snakes though those would be ideal 13-Jul-20 01:07 PM what exactly is the beam path? are you splitting with the dichroic? 13-Jul-20 01:07 PM (are both going to burn you?) 13-Jul-20 01:07 PM or cancerize 13-Jul-20 01:14 PM This is how we do some 13-Jul-20 01:14 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-DEF69.jpg 13-Jul-20 01:41 PM gotta love the glasses that block 800nm but not 400nm, so when I block the beam with paper I just see SHG 13-Jul-20 04:44 PM Beam comes from telescope to the left, and it's more of a beam splitter than a dichroic. I dunno why I said dichroic 17-Jul-20 08:55 AM FWIW, I did not get the rubidium clock. It was the perfect storm of NOPE. NASA Apollo collectors bidding against Patek Philippe collectors driving the price way beyond the auction estimate. I was wondering if that was going to happen when I saw the auction announced on a watch/clock site. $6500 + 25% buyers premium. 17-Jul-20 08:55 AM https://www.rrauction.com/PastAuctionItem/3425891 17-Jul-20 11:13 AM :D 18-Jul-20 11:34 AM @pbx/peterbjornx cool adapter! 24-Jul-20 01:30 PM https://cdn.discordapp.com/attachments/729047968547733515/736317030151749633/3lkpoKviVjoeh1fQ2PV66MrKJfwgMfIc3jC8Mah0Aw778g-gQYiZKS3dXScHgTeVdqP3YgKHZYdocZqxHb6XX1lA7lciQl_IAe7K.png https://cdn.discordapp.com/attachments/729047968547733515/736316992037847111/I_8lPw7_OhKLS_XDYmHMBZ_BIDABMfm6op9NCMDR8HAW7N2hki_tPPTnOn6tDygISm_fSAIzzZ5icOlXPGNJ34r9Zwx9mt2BrVjD.png got some cool stuff today 24-Jul-20 01:31 PM ohh neat is that an ancient q switch? 24-Jul-20 01:36 PM yeah old russian stuff its a lithium niobate EOM 24-Jul-20 01:36 PM top is a nd:yag rod that i now need to figure out how to polish/lap and then get a pumping system for it 24-Jul-20 01:39 PM nice! 24-Jul-20 01:48 PM pretty cool! 24-Jul-20 03:48 PM Somewhere I have a nice salvaged Ti:Sapphire rod I always intended to hand to a jeweler to play with. 24-Jul-20 03:50 PM oh shiet Ti:Sapphire is super hard to get from what ive seen 24-Jul-20 03:50 PM at least for like a random person 24-Jul-20 03:55 PM I've seen two show up under $500, mounted, on ebay. That's it 24-Jul-20 03:56 PM Mine used to be at the heart of a Spectra Physics Tsunami. It died an ignominious fire sprinkler related death. 24-Jul-20 03:57 PM The thing that bites is that they get thrown out not infrequently 24-Jul-20 03:57 PM because despite being hard to damage, well, you're not making proper use of it if you're not close to damaging it 24-Jul-20 03:59 PM they get thrown out??? aaaaaaaaahhhhhhh 24-Jul-20 04:05 PM you don't really want a holy tisaph 24-Jul-20 04:05 PM since they're often only like 1-3mm long anyways 24-Jul-20 05:12 PM I’ve faceted synthetic sapphire before. 24-Jul-20 05:12 PM 50k grit diamond polish on a ceramic lap. Makes an awful noise. 24-Jul-20 05:13 PM thats good to know have u lapped yag before? 24-Jul-20 05:14 PM At least it doesn’t have cleavage. 24-Jul-20 05:14 PM I am still bitter about the topaz I faceted and then found that the table was an impossible to polish cleavage plane. 24-Jul-20 05:14 PM i was thinking of trying a ceramic lap with diamond paste for yag 24-Jul-20 05:16 PM Nah. 24-Jul-20 05:16 PM Linde A (aluminum oxide) on a tin alloy lap. 24-Jul-20 05:17 PM for yag? ok will look into it 24-Jul-20 05:17 PM Well, keep in mind I am talking about tiny gemstone facets. 24-Jul-20 05:18 PM oh ok yeah may be different for a rod 24-Jul-20 05:18 PM I have no idea how to go about polishing laser crystals. 24-Jul-20 05:19 PM ah ok but may be similar 24-Jul-20 05:19 PM the target is 0.1 wavelengths 24-Jul-20 05:19 PM according to everything I read 24-Jul-20 05:20 PM You may need multiple polishes then. A jeweler just cares about whether scratches are visible at 10x magnification. 24-Jul-20 05:20 PM yeah would have to check with an optical flat probably 24-Jul-20 05:20 PM I’m not sure how that translates to wavelength. 24-Jul-20 05:20 PM Also keep in mind that one doesn’t just walk into Mordor, er, I mean, start polishing. 24-Jul-20 05:21 PM the thing that really worries me is if I side pump it i need to make the circular part clear 24-Jul-20 05:21 PM You’re going to need progressive cutting laps. 24-Jul-20 05:21 PM Each lap, depending on its grit, damages X distance into the crystal, making a perfect polish possible. 24-Jul-20 05:23 PM yeah i read about that but since its so small each lap can be pretty small im hoping 24-Jul-20 05:24 PM That’s why you see gem cutters hog off material with a diamond saw, then rough shape at, say, 260 grit, then recut the whole stone smaller at, say, 600 grit, putting in all the facets, then recut again at 1200 grit, then start polishing. 24-Jul-20 05:25 PM just get a ton of really strong flashlamps 24-Jul-20 05:25 PM then it won't matter what you do 24-Jul-20 05:25 PM lol 24-Jul-20 05:25 PM Hopefully lapping/polishing it isn't too much for me 24-Jul-20 07:22 PM I second the stupidly strong flashlamp suggestion 25-Jul-20 11:05 AM Do you also have a drawer in the back of scratched-beyond-use optics? 25-Jul-20 11:40 AM Not all of them in there are beyond use, but yes 25-Jul-20 11:41 AM I have some here where the substrate itself has some bad grooves 25-Jul-20 10:08 PM flash tubes are easier to obtain than i expected 25-Jul-20 10:12 PM They need substantial cooling 25-Jul-20 10:12 PM if they are run continuously or even if pulsed? 25-Jul-20 10:12 PM haha 25-Jul-20 10:13 PM i mean either way id rather deal with the pain of water cooling than trying to obtain an 808nm diode bank lol 25-Jul-20 10:13 PM http://publish.illinois.edu/ae-lambros/files/2017/07/Lab-Series-Users-Manual_Nd_YAG.pdf 25-Jul-20 10:13 PM they need several litres per minute of cold water 25-Jul-20 10:18 PM oh boy 25-Jul-20 10:18 PM time to pulse it like once a minute lol 25-Jul-20 10:41 PM I mean 50Hz -> 1Hz should in theory bring 5L/min to 0.1L/min 25-Jul-20 10:41 PM IDK what do you want to do with the YAG? 25-Jul-20 10:43 PM tbh i dont have a specific goal in mind i wanna see if i can get it to work first then maybe try q switching and/or mode locking 25-Jul-20 10:43 PM ik it sounds kinda dumb 25-Jul-20 10:43 PM just like a fun project tbh 27-Jul-20 12:40 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-D7D2F.jpg 27-Jul-20 12:40 PM RIP mirror 27-Jul-20 12:40 PM oops 27-Jul-20 12:45 PM oof what happened 27-Jul-20 12:51 PM Too much power 27-Jul-20 12:52 PM tf kinda lasers r u using daaang 27-Jul-20 12:54 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-46049.jpg 28-Jul-20 10:23 AM https://streamable.com/2ve3q5 testing a diode finally got my diy buck driver to work 28-Jul-20 10:23 AM also yeah i have good goggles 28-Jul-20 11:48 AM Anyone have some DIC/nomarksi/wollaston prisms/optics they want to get rid of? I'd like to try and retrofit my fluorescent microscope 30-Jul-20 06:00 AM This might be a stupid question, but how bad is ~400nm light to a DSLR camera? Thinking about adding UV illumination to my microscope to get that slight bit of extra resolution 30-Jul-20 06:00 AM Dont wanna burn out the sensor though 30-Jul-20 07:11 AM I'd be shocked if it would matter, with some ND filtering we hit normal webcams with 400nm femto beams all the time. it takes some stupidity for us to burn them doing that 30-Jul-20 08:43 AM never had probs with 400nm thb 30-Jul-20 08:43 AM but only low power 30-Jul-20 08:43 AM it's more like that I can't get enough sensitivity for <= 400nm in my case 30-Jul-20 09:08 AM CMOS sensors are surprisingly hard to damage 30-Jul-20 09:44 AM well we use them for aligning the focii of multiple beams together 30-Jul-20 09:44 AM one group I know that does that burns several and enacted a "burn a camera, buy a cake" policy 30-Jul-20 10:04 AM I'm not saying it can't be done, but the detector array we have can take our pulsed dye laser to the face no problem 30-Jul-20 10:04 AM Which still surprises me tbh 30-Jul-20 10:04 AM So that would be q-switch regime 30-Jul-20 10:07 AM Focused? 30-Jul-20 10:10 AM No. It would die if it was focused 03-Aug-20 04:00 PM set it up today 03-Aug-20 04:00 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Rkeq6uYNlIC-qLXvY1o-Ew3TBftu7zKgAVVZ6xmZNf-C9956.png 03-Aug-20 04:39 PM whatcha gonna do with it? 03-Aug-20 05:33 PM might put it in a pointer or something 03-Aug-20 05:33 PM Or might change the lens i used and use it to burn some stuff lol 03-Aug-20 07:24 PM bet you could dim it and find some interesting fluorescense in stuff, depending on the wavelength 03-Aug-20 07:24 PM i have a chonky diode array incoming that i was sort of thinking about using for, like, ablating sample surfaces in vacuum 03-Aug-20 07:24 PM idk focusing tho 03-Aug-20 07:33 PM hmm @qualia let me know if you get something like that working, gives me maldi ideas if it’s in the 300-350nm region 03-Aug-20 07:33 PM yeah kinda like that 03-Aug-20 07:33 PM my thing is apparently 8 3.75W diodes @ 455 nm and i think it was from a laser projector 03-Aug-20 07:33 PM so maybe like. one of them 03-Aug-20 07:33 PM i could pump barium's D5/2 state very slowly 03-Aug-20 09:08 PM oh yeah ill shoot it at some fluorescein when i get the chance 03-Aug-20 09:08 PM should be fun 03-Aug-20 09:14 PM You can pump a ruby with that 03-Aug-20 09:37 PM yeah need to get a ruby crystal at some point 03-Aug-20 09:37 PM my thing is apparently 8 3.75W diodes @ 455 nm and i think it was from a laser projector @qualia those arrays are pretty insane 04-Aug-20 01:01 PM https://cdn.discordapp.com/attachments/426053961624190986/740295703821156433/unknown.png 04-Aug-20 01:01 PM gotta love green 07-Aug-20 01:41 PM Finally got a bid in a US based camera that I want for the toolmaker's microscope as an 'automated' inspection (optical comparator) tool, combined with tablet and some kind of server (rpi may be powerful enough for my needs) 07-Aug-20 01:41 PM we'll see in a few days when it ends if it stays low enough 12-Aug-20 10:36 AM So uh... Mirrors for combining 800n, 227nm, and 330nm? 12-Aug-20 11:02 AM so I am working on a QKD experiment using air as a medium - just finished site surveys and scouting for alternate locations, etc 12-Aug-20 11:02 AM so right now I am thinking about a transmitter and receiver setup 12-Aug-20 11:02 AM before I spend money on anything like polarizing beamsplitters, etc 12-Aug-20 11:02 AM I am going to try to do single photon counting and detection of the beam from the two locations 12-Aug-20 11:02 AM it's unlikely that I am going to have access to our main proposed site for a while, which is about 4.08 km away 12-Aug-20 11:02 AM so I am doing the experiment from the alternate location - 1.54 km away 12-Aug-20 11:02 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-21DF1.png 12-Aug-20 11:02 AM so I am wondering if anyone has dealt with single photon counting, etc 12-Aug-20 11:02 AM I am working with green lasers since blue-green wavelengths of light seem to be more optically transmittable in air 12-Aug-20 11:02 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/transmission-9F57C.png 12-Aug-20 11:02 AM and I am looking at using avalanche photodiodes for this 12-Aug-20 11:02 AM I do realize that the responsivity of APDs seem to be lower at the lower wavelengths of light 12-Aug-20 11:02 AM and higher at NIR or IR 12-Aug-20 11:02 AM so I am also wondering if that will affect receiver sensitivity 12-Aug-20 11:07 AM oh boy aligning that is gonna be fun 12-Aug-20 11:08 AM tell me about it - I think you saw some of the site survey pics on styro's Discord server 12-Aug-20 11:08 AM what kinda green laser r u using 12-Aug-20 11:08 AM that is to be determined also 12-Aug-20 11:09 AM gonna want something with great beam specs/low divergence 12-Aug-20 11:09 AM both the transmitting and receiving apparatus needs designing haha, and I just got to thinking about the problem 12-Aug-20 11:09 AM gl! 12-Aug-20 11:09 AM where would you find lasers if you were doing such an experiment anyway? 12-Aug-20 11:09 AM I am also thinking about how to reduce my optical power to really, really low levels 12-Aug-20 11:09 AM and yes - I am quite new to optics 12-Aug-20 11:09 AM and suppliers for optical and laser stuff 12-Aug-20 11:15 AM The classic one's would be edmund optics and thorlabs 12-Aug-20 11:15 AM We used thorlabs at work for optical tables and related tidbits 12-Aug-20 11:16 AM right now I am looking Hamamatsu Photonics 12-Aug-20 11:16 AM looking at their APDs 12-Aug-20 11:16 AM Yeah they likely have some good APD's 12-Aug-20 11:19 AM Looking at S8664-1010 now 12-Aug-20 11:19 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-39471.png 12-Aug-20 11:19 AM choosing this because it seems to have better responsivity and quantum efficiency 12-Aug-20 11:19 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-63DCE.png 12-Aug-20 11:21 AM i was not aware QKD was ever done in free air, thought it was all fiber coupled 12-Aug-20 11:21 AM there have been experiments done in free air 12-Aug-20 11:21 AM like from ground to satellites 12-Aug-20 11:21 AM done by a few Chinese teams 12-Aug-20 11:22 AM oh neat 12-Aug-20 11:23 AM I have a physicist who's superivising us on this - and he says that now we confirmed LOS, we should try to get single photon counting done first 12-Aug-20 11:24 AM seems reasonable 12-Aug-20 11:24 AM before we consider things like how the interaction of air might cause decoherence of the photon's state, etc 12-Aug-20 11:24 AM I am thinking about the laser side of things also 12-Aug-20 11:24 AM what could be used to generate beams of single photons, etc 12-Aug-20 11:24 AM or if doing single photons itself is not a great idea 12-Aug-20 11:33 AM now a question 12-Aug-20 11:33 AM how can I order from Hamamatsu 12-Aug-20 11:36 AM I guess regularly available diodes won't work? 12-Aug-20 11:36 AM Would need some cleaning up of the beam probably 12-Aug-20 11:37 AM I am choosing this because of its sensitivity at the wavelengths of interest 12-Aug-20 11:38 AM I mean the laser itself 12-Aug-20 11:38 AM mouser or digikey carry hamamatsu kit 12-Aug-20 11:38 AM also ebay 12-Aug-20 11:39 AM oh the laser itself - I haven't thought of the laser itself yet 12-Aug-20 11:41 AM i'd advise getting all these very important details planned out a bit before buying a bunch of expensive application-specific hardware 12-Aug-20 11:41 AM jfwiw 12-Aug-20 11:41 AM yeah 12-Aug-20 11:41 AM I am not going to rush into this 12-Aug-20 11:41 AM probably want to design the circuits also and get them checked before sending any orders out 12-Aug-20 11:41 AM fun fact - this is not a university project of any sort 12-Aug-20 11:41 AM we're just a bunch of people who thought that this would be an interesting thing to do - along with other experiments in the future 12-Aug-20 11:41 AM thus this means this is privately funded hah! 12-Aug-20 11:41 AM so I am not going to rush into buying expensive stuff 12-Aug-20 11:41 AM I do intend to setup a web log of sorts documenting each step of the way 12-Aug-20 11:41 AM what we're doing, etc 12-Aug-20 11:51 AM so I found a technical report on NASA's site 12-Aug-20 11:51 AM about photon counting using APDs 12-Aug-20 11:51 AM going to give it a read - but later, it's so early in the morning, time for sleeps 12-Aug-20 08:07 PM Cool - so the paper describes how you can do counting in "break-down" mode 12-Aug-20 08:07 PM and proposes how you can do counting without biasing the APD to its breakdown voltage 12-Aug-20 08:07 PM and this is a pretty old paper - 1990s 12-Aug-20 08:07 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Avalanche_Photodiode_Photon_Counting_Recei-2185E.pdf 12-Aug-20 08:07 PM What I'll probably do is think about the laser transmitter also 12-Aug-20 08:07 PM choose a particular wavelength and power output and divergence 13-Aug-20 04:06 AM hmmmm 13-Aug-20 04:06 AM I am thinking of ditching APDs 13-Aug-20 04:06 AM looking at PMTs 13-Aug-20 04:06 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-9DA6A.png 13-Aug-20 04:06 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-DD54D.png 13-Aug-20 04:06 AM I mean the have a larger aperture 13-Aug-20 04:06 AM more responsive and cheaper than APDs 13-Aug-20 04:06 AM downside is that they're fragile of course 13-Aug-20 04:06 AM and needs quite a high bias voltage 13-Aug-20 04:06 AM in both cases I need to figure out dark count 13-Aug-20 12:43 PM i think with either a PMT or an APD you're gonna need some nontrivial optics in front of it anyways 13-Aug-20 12:43 PM but PMTs can be had quite inexpensively on ebay, and getting them going is not terribly complicated 13-Aug-20 12:44 PM I might be wrong but it looks like you're looking for a hybrid pmt 13-Aug-20 12:44 PM like the R10467U 13-Aug-20 12:44 PM https://www.ebay.de/itm//184393320902 They're not too expensive on ebay, but I don't know where you are, if they ship to you ^^ 13-Aug-20 12:52 PM -8500V photocathode voltage 13-Aug-20 12:52 PM hmmmm 13-Aug-20 12:56 PM -8.5 kV, rather, and that's the redline absolute maximum 13-Aug-20 12:56 PM voltage determines your gain 13-Aug-20 12:57 PM oops 13-Aug-20 12:57 PM I'm sleepy haha 13-Aug-20 12:57 PM but yeah 13-Aug-20 12:57 PM getting a few kV is my concern 13-Aug-20 12:57 PM how to provide these supplies in a compact way 13-Aug-20 12:57 PM that be transported easily to rooftops 13-Aug-20 12:57 PM where the experiments are taking place 13-Aug-20 12:59 PM a clean couple of kV isn't tooo hard to come by.. lots of little power supply modules on ebay for driving PMTs or biasing semiconductor detectors show up online 13-Aug-20 12:59 PM ^ +1 13-Aug-20 01:00 PM you will also need a couple hundred volts for biasing the APD too if you go with a hybrid PMT 13-Aug-20 01:00 PM (.. i think?) 13-Aug-20 01:00 PM yeah that I am aware 13-Aug-20 01:00 PM haven't goofed around with mine just yet 13-Aug-20 01:01 PM me neither I just bought a lot because they're were cheap and might come in handy one day ™️ 13-Aug-20 01:01 PM also because they're pretty cool tbh 13-Aug-20 01:01 PM valid :D 13-Aug-20 01:02 PM these HPDs look small 13-Aug-20 01:02 PM if I can work out some battery operated supply for these 13-Aug-20 01:02 PM these would be awesome - I think 13-Aug-20 01:04 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200813_220337-45ABF.jpg 13-Aug-20 01:04 PM they're pretty cute 13-Aug-20 01:04 PM i literally just grabbed my c-mount lens to take a picture lmao 13-Aug-20 01:04 PM and they take C mount! 13-Aug-20 01:04 PM I see! 13-Aug-20 01:04 PM tempting 13-Aug-20 01:08 PM do it 13-Aug-20 01:08 PM not so fast haha 13-Aug-20 01:08 PM going to talk to my team 13-Aug-20 01:08 PM well, at least the other team member who knows electronics too 13-Aug-20 01:08 PM then we can work out a good way to power these things 13-Aug-20 01:08 PM okay, time for sleeps 13-Aug-20 01:08 PM thanks for the link ^^ 13-Aug-20 01:11 PM good night! 13-Aug-20 01:11 PM more like close to morning where I am 13-Aug-20 01:11 PM 4:12 am here 13-Aug-20 01:12 PM also the gain if these hybrid PMTs is pretty linear, so 1 or 2 kV might also suffice for your application 13-Aug-20 01:12 PM well then *sleep well 13-Aug-20 01:12 PM haha, cya 13-Aug-20 01:12 PM and I'll look at the specs and datasheets more carefully 13-Aug-20 08:31 PM so I am getting a few of this 13-Aug-20 08:31 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-B1451.png 13-Aug-20 08:31 PM then add some sort of multiplier in front 13-Aug-20 08:31 PM this outputs 900v 13-Aug-20 09:53 PM hmmmm 13-Aug-20 09:53 PM I wonder 13-Aug-20 09:53 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/HTB1GGRDSpXXXXc1aXXXq6xXFXXXu-F7E4D.png 14-Aug-20 08:21 AM So languages are not my thing. I can barely speak my native English, but Block? 14-Aug-20 08:28 AM I mean 14-Aug-20 08:28 AM it is Chinese stuff 14-Aug-20 08:28 AM they misspell stuff all the time 14-Aug-20 12:09 PM those negative ion generators and other monolithic high voltage power supplies are a lot of fun to experiment with 14-Aug-20 12:10 PM Oh? 14-Aug-20 12:10 PM the regulation may not be very good, especially for photocathode biasing where little ripples can turn to big swings in your effective gain 14-Aug-20 12:10 PM so you may need to design a filtering frontend for your needs, or not. a good high voltage oscilloscope probe is extremely handy here 14-Aug-20 12:11 PM Oh yeah - I plan to order a HV probe that's for sure 14-Aug-20 12:11 PM A 500 MHz scope isn't fun to kill 14-Aug-20 12:14 PM ALSO, if the original purpoae of the module was, like, a stun gun or bug zapper, you will have a lot of frontend capacitance for delivering big beefy sparks, without having much actual current delivering capacity in the voltage multiplication stage. this can help a little with regulation, buuut it can also mean the difference between an accidental arc flashover that slightly locally degrades your sensor performance and a flashover that instantly and irreparably destroys it. so, current limiting isn't a bad idea too 14-Aug-20 12:14 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/s-l400-83851.jpg 14-Aug-20 12:14 PM This is what I am looking at 14-Aug-20 12:14 PM 1000:1 probe 14-Aug-20 12:15 PM those are.. okay. really noisy, lots of EM pickup, although that one looks like it's got an actual BNC out so maybe it'll fare better than mine 14-Aug-20 12:15 PM i sniped a cheap Tek P6015 bc i do a lot of HV nonsense and it was a very sound decision 14-Aug-20 12:16 PM Ah 14-Aug-20 12:16 PM I never touched or thought of dealing with HV beyond like 500-600v until really recently 14-Aug-20 12:17 PM those ones like the one you posted also have the downside of not having great frequency response, which is somewhat important for ripple measurements 14-Aug-20 12:18 PM Ah 14-Aug-20 12:18 PM The HPD states that the maximum current rating for the photocathode is only about 200 pA 14-Aug-20 12:18 PM I am thinking this is going to be very little amounts of current? 14-Aug-20 12:18 PM I am thinking about adding some filters however on the output 14-Aug-20 12:18 PM I saw some XP Power HV modules 14-Aug-20 12:18 PM But they're really really expensive 14-Aug-20 12:18 PM Like $200+ USD per module 14-Aug-20 12:26 PM yeah, you just need what's called a 'bias supply' -- lots of voltage, basically no current, very good regulation 14-Aug-20 12:26 PM that last bit is rather trickier to DIY 14-Aug-20 12:27 PM Yeah - keeping the o/p ripple down is not going to be so easy 14-Aug-20 12:28 PM $200 isn't terribly unreasonable for a new supply appropriate for this; def. would recommend cross checking with ebay 14-Aug-20 12:28 PM I just wonder if my filter will load the voltage down on this negative ion module haha 14-Aug-20 12:30 PM 5kV variable bias supplies for nuclear instrumentation sometimes show up cheaply on ebay, but then you'd need a bin to stick it in (they usually use the line voltage pins, though, so could carefully mod it to plug into an outlet) 14-Aug-20 12:30 PM XP Power, Spellman, Glassman, Bertran, Lambda, they all make good HV power supplies 14-Aug-20 12:30 PM probably others 14-Aug-20 12:31 PM One of my requirements here is that I am going to have to battery power this setup :P 14-Aug-20 12:31 PM That's why I have been looking at modules that can accept say, 12v and spit out a few kV 14-Aug-20 12:31 PM Since where I am running the experiment, there's no mains access 14-Aug-20 12:31 PM It's all on the rooftops 14-Aug-20 12:43 PM You’re looking for like 8kV right? 14-Aug-20 12:43 PM 3kV and under supplies are overly common 14-Aug-20 12:43 PM We have a whole rack full of them just sitting around, many excellent 14-Aug-20 12:44 PM it doesn't have to be 8 kV 14-Aug-20 12:44 PM 3 should also be plenty 14-Aug-20 12:44 PM Then tbh $200 seems more than you should have to spend for even a really good one 14-Aug-20 12:44 PM (Says the person who recently spent 6k on four supplies) 14-Aug-20 12:45 PM I have no idea whar the new pricing is 14-Aug-20 12:45 PM I know that new single channel NIM hpvs stuff starts at 1k 14-Aug-20 12:45 PM They’re ~$500-1500 each for just the modules, double that with enclosures, from my quoting around 14-Aug-20 12:45 PM You can always spend more of course 14-Aug-20 01:24 PM the cheapest 'nice' HV supplies i've ever found were all nim modules, which need a bin ($free-$few 100ish-$$$$ new), but then once you have that you can find the occasional old 5kV HPGe bias supply module for like $50 14-Aug-20 01:24 PM my 30kV 1mA spellman extraction supply was a $40 ham swap meet steal 14-Aug-20 01:24 PM and my chonky & moderately broken 30kV/32mA CV/CC Glassman was uhhh like $700.. ish 14-Aug-20 01:38 PM I need to get an hv supply 14-Aug-20 01:38 PM Don’t even need a nice one just... don’t need the hellscape thrown together one I have 15-Aug-20 09:47 AM @SleepyOwl Joyce I own a similar 1000:1 probe. Mine has banana plug leads for my Fluke multimeter. 1 GOhm impedance. Very important because I use it to test Geiger counter bias supplies that have negligible current, where a 10 MOhm DMM looks like a dead short. 15-Aug-20 09:49 AM I see 15-Aug-20 09:49 AM I was wondering about the input impedance though 15-Aug-20 09:49 AM because it seems like it uses the DMM/scope input impedance as part of the voltage divider 15-Aug-20 10:00 AM I am not sure how it would affect things if I am connecting it to a scope 15-Aug-20 10:00 AM since the scope has a 1 Megohm input impedance 15-Aug-20 10:00 AM compared to 10 Megohm of a DMM 15-Aug-20 11:24 AM I’m not sure. I know the probe I have is designed for a multimeter with 10 MOhm impedance. 15-Aug-20 11:27 AM I'll check the one I want to order later in the day 15-Aug-20 11:27 AM It comes with a cable with a BNC plug 15-Aug-20 11:27 AM So I am assuming it is meant for scopes 15-Aug-20 11:27 AM But I shan't assume especially if I am going to do anything that could kill an expensive scope xD 15-Aug-20 11:27 AM Hmmmm @rfs any thoughts? 15-Aug-20 12:08 PM I'd venture a guess that if it has BNC it's for a scope 15-Aug-20 12:08 PM and hopefully has a way to compensate it or has some internal termination so that the scope input impedance matters less. 15-Aug-20 01:07 PM @SleepyOwl Joyce sounds like an awesome project! how are you planning to determine which photons are the ones you're looking for? collinear cylinders to block most other light? i guess frequency filtering would make it much easier, though curious how much absorption there would be from particulates in air 15-Aug-20 01:10 PM So I am using laser light of a specific wavelength - I've not all the details fleshed out yet, but I am thinking of some sort of material or filter that would allow light of specific wavelengths through 15-Aug-20 01:10 PM i'm attempting a single photon tx/rx setup at home as well (and have no idea what i'm doing), these were the types of single photon detectors i found (settled on a cheap PMT for now) * Vacuum-based * Photomultiplier Tube (PMT) * Multi Anode Photomultiplier Tube (MAPMT) * Micro-Channel Plate (MCP) * Hybrid Photon Detector (HPD) * Solid-state * Electron-Multiplying CCD (EMCCD) * Single-Photon Avalanche Diode (SPAD) * SPAD Array * Silicon Photo-Multiplier (SiPM) * Quanta-Image Sensor (QIS) * Cryogenic-temperature based * Superconducting Nanowire Single-Photon Detector (SNSPD) * Transition-Edge Sensors (TES) 15-Aug-20 01:10 PM I am looking at using green lasers - primarily because blue-green light is better transmitted in air 15-Aug-20 01:10 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/transmission-56F9A.png 15-Aug-20 01:11 PM SiPMs won't do you any good for single photon counting 15-Aug-20 01:11 PM cool! you can get narrow passband filters for cheap on ebay 15-Aug-20 01:12 PM I see! I am looking at the Hamatsu Hybrid Photodetector tubes for the photon counting and detection - because of the cost haha 15-Aug-20 01:12 PM but my concerns are the quantum efficiencies of these devices 15-Aug-20 01:12 PM which top out at ~40% 15-Aug-20 01:12 PM so I don't think that single photon transmission of data would be that feasible in open air 15-Aug-20 01:12 PM but rather, a quasi single photon stream of sorts 15-Aug-20 01:12 PM What me and my teammembers want to do for a start 15-Aug-20 01:14 PM @GigaSquirrel oh, why? was reading docs that it would, eg https://indico.cern.ch/event/716539/contributions/3246002/attachments/1799871/2935319/present.pdf 15-Aug-20 01:14 PM Is to start off with a quasi single photon source - like a laser behind a variable optical attenuator 15-Aug-20 01:14 PM then see if the receiver can even detect the photons coming from the source 15-Aug-20 01:15 PM the SiPMs are just many APDs in geiger mode in parallel iirc, and once a photon has hit an apd it can't trigger any others 15-Aug-20 01:16 PM cool, what would you use to attenuate? any general writeup or thoughts you have on the build? 15-Aug-20 01:17 PM I am looking at optical attenuators like these for the setup - they look expensive however and I am trying to see if I can relatively cheapy procure one 15-Aug-20 01:17 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/VA-BB-191_400w-B8B61.png 15-Aug-20 01:18 PM is that just a waveplate with a cube? 15-Aug-20 01:18 PM Oh yeah 15-Aug-20 01:19 PM @GigaSquirrel hmm okay, is this info on wikipedia incorrect or am i misunderstanding it? https://www.wikiwand.com/en/Silicon_photomultiplier 15-Aug-20 01:19 PM That's $4000? 15-Aug-20 01:19 PM What are you doing, a cube + waveplate for one wavelength should be <$1000 15-Aug-20 01:20 PM I see - I mean optics is something I am quite new to so I am still figuring things out on that front 15-Aug-20 01:21 PM I guess you're missunderstanding it ^^ One single photon avalanche diode can be triggered by one photon, and you detect light pulses of multiple photons by detecting multiple apds being triggered 15-Aug-20 01:21 PM it's just manymany binary switches with a resistor in series in parallel, so every toggeled switch gives a bit more current 15-Aug-20 01:22 PM the general idea for the initial experiments I am looking is as follows: Laser source at 532 nm --> Optical attenuator --> Air --> Optical pass filter --> HPD --> Instrumentation electronics 15-Aug-20 01:23 PM so I guess it would be good to detect a single photon 15-Aug-20 01:23 PM ...I'm sorry, It's a bit late and now I have confused myself why I though that it was not good to do so 15-Aug-20 01:24 PM or even just to correlate say a count of few hundred photons in a steam to the laser 15-Aug-20 01:24 PM so trying to differentiate noise and the signal of interest 15-Aug-20 01:24 PM that's the first step 15-Aug-20 01:24 PM huh 15-Aug-20 01:24 PM so this is how a variable attenuator of sorts is built 15-Aug-20 01:24 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-01485.png 15-Aug-20 01:24 PM link to app note: https://www.newport.com/medias/sys_master/images/images/h24/h0e/8797301637150/Variable-Attenuator-for-Lasers-App-Note-26.pdf 15-Aug-20 01:24 PM @idmb so I am assuming that the motor turns the waveplate and the polarizer blocks a certain percentage of light based on the rotation of the waveplate? 15-Aug-20 01:36 PM yeah here let me show you one in our lab lol 15-Aug-20 01:36 PM sure! 15-Aug-20 01:37 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-C829F.jpg 15-Aug-20 01:37 PM Pulse goes through the waveplate in the rotation mount at the top 15-Aug-20 01:37 PM And then the two polarization go straight or reflected through the cube 15-Aug-20 01:39 PM ah 15-Aug-20 01:41 PM Knowing the specifics of what you need quality-wise, you most likely don't need the fancy $4000 mounted system 15-Aug-20 01:41 PM beam diamter too etc. 15-Aug-20 01:41 PM Those SM1 mounts are nice and all too, but expensive. 15-Aug-20 01:41 PM I certainly don't - the question would be how to make a setup that I can easily bring up to a roof without risking breaking expensive optics 15-Aug-20 01:41 PM 3d print mounts 15-Aug-20 01:42 PM which brings me to a question 15-Aug-20 01:42 PM 3D printing stuff like this only saves money if you don't value your time 15-Aug-20 01:42 PM how closely would the waveplate and polarizer have to be? 15-Aug-20 01:42 PM or how far? 15-Aug-20 01:42 PM how? wouldnt it be super cheap and fast 15-Aug-20 01:42 PM unless ur counting time it takes to model it ig 15-Aug-20 01:43 PM Yeah looks like a cube and waveplate can be ~$200 and ~$250 each. 15-Aug-20 01:43 PM Time to model matters 15-Aug-20 01:43 PM The physics says it doesn't matter how close they are, but air does affect polarization a bit 15-Aug-20 01:44 PM there are some models online for mount stuff 15-Aug-20 01:46 PM the rotation part would be interesting for a DIY attenuator mount/setup 15-Aug-20 01:46 PM using 3D printed stuff 15-Aug-20 01:46 PM although I am not really great at 3D modelling 15-Aug-20 01:46 PM passes the task to a team member 15-Aug-20 01:47 PM @GigaSquirrel ahh no worries, i appreciate the info! any info helps me learn 15-Aug-20 01:48 PM yeah i mean ig i value my time pretty low 15-Aug-20 01:48 PM I mean I don't care about time too much 15-Aug-20 01:48 PM since the money for buying these parts is my bottleneck 15-Aug-20 01:48 PM nice thing tho with 3d printing is u can add custom bits 15-Aug-20 01:49 PM I don't mind figuring out the 3D printing bits with teammates, etc 15-Aug-20 01:49 PM @SleepyOwl Joyce ahh cool, thanks for the info! i'm attempting to do single photon source with multiple passes of neutral density filters, doubt it will work but going to give it a shot 15-Aug-20 01:50 PM yeah and modeling is fun so if u add entertainment value its pretty worth 15-Aug-20 01:50 PM Let us know how it goes @samy! 15-Aug-20 01:50 PM And ngl 15-Aug-20 01:50 PM I didn't think too many folks were trying to do QKD 15-Aug-20 01:50 PM after this initial experiment 15-Aug-20 01:50 PM the next problem to tackle - how do you send single photons or quasi single photon streams 15-Aug-20 01:50 PM without the information decohering in air? 15-Aug-20 01:50 PM of course while we're going to do some sort of "in lab" test 15-Aug-20 01:50 PM but one of the goals is to get this working at some distance away 15-Aug-20 01:50 PM which in the initial stages - would be on the roofs of two buildings, separated 1.54 km away 15-Aug-20 01:50 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/5730e57c-d668-48d3-893d-961a46751cb2-DB6B3.png 15-Aug-20 01:50 PM then after the pandemic situation gets better and we can get approvals to go to a location 15-Aug-20 01:50 PM 4.05 km is what we'll try 15-Aug-20 01:50 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/aec45fc1-c285-42e3-993a-28b5ac30a8cd-4A460.png 15-Aug-20 01:50 PM there's no specific reasons for the two locations only beyond the fact that they're one of the few publicly accessible roof gardens here in Singapore 15-Aug-20 01:50 PM roofs are typically out of bounds, and these locations have accessible roofs that have known line of sight (at least based on our site survey) 15-Aug-20 02:03 PM ahh 15-Aug-20 02:05 PM I am going to be creating a site for logging down our experiments and setup pretty soon 15-Aug-20 02:05 PM just that right now I want to make sure with the rest on how exactly we're going to carry this out and what we need to buy/procure 15-Aug-20 02:05 PM for now I will be asking questions and posting things here 15-Aug-20 08:50 PM hmmm 15-Aug-20 08:50 PM would anyone trust beamsplitters from China? 15-Aug-20 08:50 PM https://www.aliexpress.com/item/32659411614.html?spm=2114.12010612.8148356.22.4481361avENnGU 15-Aug-20 09:01 PM For an attenuator? Sure. Do you care about polarization? No 15-Aug-20 09:02 PM oh? 15-Aug-20 09:02 PM I was thinking of getting the 1/2λ plate, polarizing beamsplitter and optical band pass filter from that company/seller 15-Aug-20 09:04 PM So cubes are typically / often used for getting clean polarization 15-Aug-20 09:04 PM and then later on, filtering polarizations 15-Aug-20 09:04 PM If you give it vertical light, even though it transmits horizontal it will transmit some of the vertical 15-Aug-20 09:06 PM yeah - that I am aware 15-Aug-20 09:06 PM so that being said, if I needed to separate out polarizations of light cleanly, what would I need to do? In let's say, a receiver setup where we measure polarization? 15-Aug-20 09:09 PM you'd need to... have cubes that work properly 15-Aug-20 09:09 PM or use thin film polarizers, even 15-Aug-20 09:09 PM https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=739&pn=PBS101 15-Aug-20 09:09 PM they list the transmission and reflection of opposite polarizations, so you can figure out the "leakage" 15-Aug-20 09:10 PM ah 16-Aug-20 09:27 AM All I can tell you is there's about a 0% chance we would order chinesium optics like that, and we've got a KYKY turbopump and PVC sewage pipe for vacuum lines. 16-Aug-20 09:27 AM But we live and die for polarization & spectral quality. 16-Aug-20 09:38 AM I see 17-Aug-20 08:21 AM @GigaSquirrel so I won that auction haha 17-Aug-20 08:21 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-0AEA0.png 17-Aug-20 08:21 AM for the HPD tubes 17-Aug-20 08:21 AM thanks for the heads up! 17-Aug-20 08:21 AM that being said - I wasn't able to find other listings for HPDs on ebay 17-Aug-20 08:21 AM hmmmm 17-Aug-20 08:31 AM now gotta think about how to design the power supplies for these 17-Aug-20 08:41 AM haha, congrats! 17-Aug-20 08:41 AM yeah, I have not seen any others, but this seller is constantly selling them for cheap 17-Aug-20 08:43 AM I see 17-Aug-20 08:43 AM now we can get into some real circuit design for the receiver part 17-Aug-20 08:43 AM I need to think about the transmitter part 17-Aug-20 08:43 AM I am going to use 532nm lasers 17-Aug-20 08:43 AM but I need to think about the output power of whatever LD we use 20-Aug-20 07:36 PM Soooo does anyone know what standards Nikon might have been using for threading on their objective mount in the 80s? 20-Aug-20 07:36 PM My new (old) microscope has a 3x objective and no others, and I can't really find the part number for the objective anywhere 20-Aug-20 07:36 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200820_220914-4F298.jpg 20-Aug-20 07:36 PM I can't find any similar objective mounts anywhere? 20-Aug-20 07:58 PM It might be m52?? 20-Aug-20 07:58 PM Calipers time it is I guess 20-Aug-20 08:17 PM Outer diameter of threads is almost exactly 42 mm, might be m42-fine? 20-Aug-20 08:17 PM I'm new to this, does that sound right? 20-Aug-20 08:17 PM M42 was an old photo lens standard, til. 20-Aug-20 09:21 PM M42 and T-mount are both 42mm diameter threaded lens mounts for cameras 20-Aug-20 09:21 PM They have different thread pitches, though 20-Aug-20 09:25 PM Welp 20-Aug-20 09:25 PM @idmb I bought an m42 adapter from thorlabs, we'll know in like 3 days if I screwed up! 20-Aug-20 09:25 PM That being said, if I had been smart I would have gone downstairs and grabbed my metric thread gauges 20-Aug-20 09:25 PM But too late oh well. 21-Aug-20 12:13 AM So this calorimeter arrived moments ago 21-Aug-20 12:13 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20200821_151039-61E4A.jpg 21-Aug-20 12:13 AM neat 21-Aug-20 12:13 AM do you have readout electronics for it? 21-Aug-20 12:14 AM that's the thing I am about to get to 21-Aug-20 12:14 AM I could just buy the display unit 21-Aug-20 12:14 AM or I could design my own electronics 21-Aug-20 12:14 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-10AA3.png 21-Aug-20 12:14 AM they give the pinout anyway 21-Aug-20 12:14 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-61E48.png 21-Aug-20 12:14 AM either way - there's just one problem 21-Aug-20 12:14 AM Because this is a used calorimeter 21-Aug-20 12:14 AM there's no documentation of previous calibrations, etc 21-Aug-20 12:14 AM they would usually write the sensitivity (in mV/W) in the 2nd page of the manual 21-Aug-20 12:14 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-D61EA.png 21-Aug-20 12:14 AM but I don't have that 21-Aug-20 12:14 AM which means that I could just buy the display head 21-Aug-20 12:14 AM but I would just be blind trusting whatever results it gives 21-Aug-20 12:14 AM especially since I don't have a 1064 nm laser of a known power to begin with 21-Aug-20 12:14 AM that's the fun part 21-Aug-20 12:14 AM so I need to figure out how to get this calibrated somehow 21-Aug-20 12:23 AM It's pretty cool that they even supply this information, usually it's just "Readout can be done over a proprietary protocol using our readout electronics" 21-Aug-20 12:23 AM you can thermally couple a resistor onto the sensor surface, let that dissipate a certain power and look for the output 21-Aug-20 12:24 AM I could try 21-Aug-20 12:24 AM once I can get this cal'ed 21-Aug-20 12:24 AM then I can work with Nd:YAG lasers 21-Aug-20 12:24 AM since this is calibrated for 1064 nm anyway 21-Aug-20 12:28 AM No I mean for calibration 21-Aug-20 12:28 AM I know 21-Aug-20 12:28 AM might not be ideal but I can't imagine the error being > 20% 21-Aug-20 12:29 AM yeah 21-Aug-20 12:29 AM I could get a stone resistor 21-Aug-20 12:29 AM have it dissipate say, a watt 21-Aug-20 12:29 AM then measure the voltage on the output of the electronics 21-Aug-20 12:29 AM yep 21-Aug-20 12:32 AM I'll see about that - gotta make a strip down to the electronics stores 21-Aug-20 12:32 AM don't have stone resistors on hand now 21-Aug-20 03:34 PM Anyone have experiencee with "Reflective Object Sensor" (QRE1113, OPB708, TCRT5000L, etc) as a form of distance measurement? they are all just an IR LED + Photodiode.. I'd basically be interested in measuring the distance (only first part listed has the small range I would want of sensitivity) of a [polished] metal surface.. I was half thinking of the [appliedscience explained] self-mixing laser interferrometry but came across these relatively simple IR solutions, that may be adequet so long as I calibrate it well enough (via gauge blocks) 21-Aug-20 03:36 PM Would those be better than the ultrasonic ones for you? 21-Aug-20 03:36 PM ultrasonic = those standard sonar modules? 21-Aug-20 03:36 PM Ideally I would like to be within 5mm of the object 21-Aug-20 03:36 PM and have sensitivity of aorund that range 21-Aug-20 03:36 PM it will basically be mixed/added to an optical/magnetic scale, for detecting distance, but there scale with the sensor head is kind of what moves (with the scale being read) until the proximity sensor gets within range 21-Aug-20 03:36 PM "moving scale" is the reference design 21-Aug-20 03:36 PM (I can find the DOI of the article if desired) 21-Aug-20 03:36 PM 10.1016/j.precisioneng.2016.08.005 21-Aug-20 03:36 PM I want to minaturize it into a handheld digital micrometer 21-Aug-20 03:36 PM Lion Precision C5-D capacitive sensor is integrated as the displacement sensor 22-Aug-20 01:18 AM Ultrasonic sensors are not good in measuring in short ranges (< 0.5 m). Most precise sensors today available are ToF sensors by ST (https://www.st.com/en/imaging-and-photonics-solutions/proximity-sensors.html) 23-Aug-20 08:22 PM Does anyone know some resources besides Boyd for nonlinear optics? Especially OPOs/DFG, and bonus points if it's more practically focused and less theoretical. In the end I mostly want to see it presented in a different way though. 23-Aug-20 08:22 PM Also, for cavity alignment, I can just monitor the power output once it's roughly aligned to really get it dead on, right? 23-Aug-20 08:22 PM I'm pretty sure my OPO woes are the cavity losses being high which makes it hang around the oscillation threshold 23-Aug-20 09:32 PM With 0 understanding, don't you want to measure a nonlinear signal for alignment? Not power? 23-Aug-20 09:40 PM It would be the nonlinear signal. Probably should have specified that I meant the signal wave power 24-Aug-20 02:32 PM wich type of OPO is it? 24-Aug-20 03:25 PM Singly resonant q-switched Nd:YAG pumped that uses angle phase matching. It's custom so there's not really any schematic I can point to 24-Aug-20 03:25 PM Though I think I had it good enough until I accidentally touched the wrong mirror and will need to start over 24-Aug-20 03:25 PM But if I did it once in like an hour I can do it again, so not a huge deal 24-Aug-20 03:25 PM Though my pump laser has a hot spot that I'm having trouble finding the cause of which is just urgh 24-Aug-20 03:31 PM Is this diode pumped? 24-Aug-20 03:37 PM No. Flashlamp 24-Aug-20 04:43 PM Planning on making a flashlamp pumped nd:yag myself 24-Aug-20 04:43 PM Need to get caps tho 24-Aug-20 06:42 PM what kinda power density do you need? if you know 24-Aug-20 06:42 PM i don't know if you need some particular threshold amount or smth 24-Aug-20 06:42 PM do u have flashtubes already? 24-Aug-20 06:51 PM @qualia yeah I calculated the general range I need. I have the tubes already 24-Aug-20 06:52 PM ah fun 24-Aug-20 06:53 PM Just need to find a good deal and stuff 24-Aug-20 06:53 PM Following this solid state laser engineering book that styro recommended for calculations and such 24-Aug-20 06:53 PM Ideally I will have 1kv at 600uf 24-Aug-20 07:11 PM series-parallel some caps? 24-Aug-20 07:18 PM Yeah that's the plan. It's just deal hunting at this point 24-Aug-20 07:18 PM And level upping my bank account lol 24-Aug-20 07:22 PM have fun! 24-Aug-20 07:22 PM I'm outta funds for cool stuff this month XD 24-Aug-20 07:22 PM but then the pay is coming in next week 24-Aug-20 07:22 PM then I can start ordering electronics for my own experiments and crap 24-Aug-20 07:22 PM haven't ordered my own flashlamp capacitor 24-Aug-20 07:22 PM I'm looking to order the Chinese 100uF, 1.4 kV capacitor 24-Aug-20 07:22 PM not that I need to charge it fully, just that it's what they use for a... given application so to speak 25-Aug-20 02:52 AM So these arrived 25-Aug-20 02:52 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20200825_174906-39F4F.jpg 25-Aug-20 02:52 AM my HPDs however - aren't here yet :/ 25-Aug-20 02:54 AM but it's a start 25-Aug-20 02:54 AM shipping from germany to the usa takes a loooong time in my experience 25-Aug-20 02:55 AM I might contact my forwarder later 25-Aug-20 02:55 AM cause the package is marked as delivered by Hermes to the forwarder 25-Aug-20 02:55 AM but status showing as pending receipt on their site 25-Aug-20 02:56 AM oh it's not even there yet? 25-Aug-20 02:56 AM I thought you meant it's stuck somewhere between De and USA 25-Aug-20 02:57 AM DE to Singapore rather haha 25-Aug-20 02:57 AM a German friend of mine said to use a forwarder 25-Aug-20 02:57 AM because the shipping times now can be long 25-Aug-20 02:57 AM so I got the seller to ship to the forwarder 25-Aug-20 02:57 AM Tracking says forwarder received it 25-Aug-20 02:57 AM but the forwarder's site says pending receipt of package 25-Aug-20 03:01 AM oh I see I just assumed you were in the USA 25-Aug-20 03:01 AM guess their site just is a bit slow 25-Aug-20 03:01 AM you assumed my location? :O 25-Aug-20 03:01 AM oh speak of the devil 25-Aug-20 03:01 AM the email saying that the package arrived just came in 25-Aug-20 03:05 AM heh, great 25-Aug-20 03:38 AM just paid for shipping 25-Aug-20 03:38 AM when the shipping itself is >60% of the product cost tho 25-Aug-20 03:38 AM the marvel of international shipping 25-Aug-20 03:39 AM why hasn't anyone invented teleporters yet 25-Aug-20 03:39 AM it will be cool if packages get teleported direct to home 25-Aug-20 03:39 AM inb4 people start teleporting mail bombs to each other 25-Aug-20 03:45 AM why hasn't anyone invented teleporters yet @SleepyOwl Joyce because the warp corrupts everything with Chaos 25-Aug-20 03:45 AM I may or may not have been reading too much Warhammer lately 25-Aug-20 03:52 AM didn't get the reference 25-Aug-20 03:52 AM right now we have an interesting optical experiment to do 25-Aug-20 03:52 AM how do you align a laser and a photodiode spaced 1.54 km away 25-Aug-20 03:52 AM it's also a little hard to spot the other location even with binoculars 25-Aug-20 03:52 AM so my teammate bought this 25-Aug-20 03:52 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200825_114653-F712C.png 25-Aug-20 03:52 AM he opened it up 25-Aug-20 03:52 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20200825_181914-D9314.png 25-Aug-20 03:52 AM so we're modifying this to blink Morse 25-Aug-20 03:52 AM while this doesn't make it any easier to align the thing precisely 25-Aug-20 03:52 AM it does make the receiver station easier to make out and spot amongst dense forests of buildings 25-Aug-20 04:00 AM @SleepyOwl Joyce If you don't need to have it working autonomously, then "regular" camera flash is your friend. We used it to align some microwave links and it worked flawlessly even in daylight with distance around 2 kilometers... 25-Aug-20 04:02 AM I see 25-Aug-20 08:41 AM oooh 25-Aug-20 08:41 AM they shipped out pretty quickly 25-Aug-20 08:41 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-73D70.png 25-Aug-20 08:41 AM so hopefully by next week as planned 25-Aug-20 08:41 AM we'll get the HPDs 25-Aug-20 09:33 AM Would a mechanism like the SLR portion of an SLR camera be used to get something like that aligned roughly first? Then what? Dial it in using some sort of screw for the azimuth and altitude? 25-Aug-20 09:33 AM I've considered that sort of point to point alignment for rural internet, there's at least one provider in the area who uses line of sight stuff 25-Aug-20 09:35 AM I was thinking of getting a riflescope for alignment of stuff 25-Aug-20 09:35 AM but in Singapore; hauling out a rifle scope is likely going to get the police called 25-Aug-20 09:35 AM cause you know... 25-Aug-20 09:35 AM riflescope = you're going to shoot someone 25-Aug-20 09:35 AM what I was intending of doing was to make a 3D printed mount for a riflescope with an alignment laser 25-Aug-20 09:35 AM so that we could mount this whole thing on a tripod 25-Aug-20 09:35 AM and look at a closeup of the receiver station + align the laser 25-Aug-20 09:35 AM but in any case 25-Aug-20 09:35 AM what I worry about is laser beam divergence 25-Aug-20 09:35 AM especially at 1.54 km away 25-Aug-20 09:35 AM so I was thinking about using a radio link to confirm alignment between transmitter and receiver 25-Aug-20 09:35 AM so for example, if the laser is pulsed and the photodetectors on the other side detect something 25-Aug-20 09:35 AM it would likely mean that alignment was made 25-Aug-20 09:35 AM even if we cannot visibly detect the beam 25-Aug-20 09:35 AM I just hope I am not over-engineering this 25-Aug-20 10:16 AM what I worry about is laser beam divergence A photodiode behind an aperture will pretty easily find you the peak intensity 25-Aug-20 03:23 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Progress1-FC4EA.jpg 25-Aug-20 03:37 PM ooh, TEA laser? 26-Aug-20 05:38 AM https://www.kickstarter.com/projects/tiltfive/holographic-tabletop-gaming/posts/2933540 26-Aug-20 12:48 PM DID YOU KNOW: disposing of large energy discharge capacitors from a residence is annoying 26-Aug-20 12:48 PM CA (Alameda County specifically) household hazardous waste people don't want anything to do with single hazmat items over 50lbs in size 26-Aug-20 12:48 PM hopefully some local transformer place will respond to my piteous pleading and not charge me $10k for the privilege 26-Aug-20 12:51 PM Ooof 26-Aug-20 12:51 PM If this werent during covid, i would have suggested dropping em at the local uni's dumpster room 26-Aug-20 12:53 PM TBH email them anyways and ask. 26-Aug-20 02:42 PM Can't you find a buyer/taker for them? 26-Aug-20 02:42 PM No HV enthusiasts within range? 26-Aug-20 02:43 PM last time I'm ever ordering something without breaking out the thread gauge first 26-Aug-20 02:43 PM that M42 port I was trying to order an adapter for? 26-Aug-20 02:43 PM @idmb you told me to check if it was m42 or T-mount? well uh 26-Aug-20 02:43 PM turns out its neither 26-Aug-20 02:43 PM its m42x0.5 26-Aug-20 02:43 PM it came with an adapter to m30x0.75. Neither of these are industry standard >.< 26-Aug-20 02:43 PM Thanks, Nikon 26-Aug-20 02:46 PM LOL 26-Aug-20 02:47 PM DID YOU KNOW: disposing of large energy discharge capacitors from a residence is annoying @qualia Why would you do that? Are they known PCBs? 26-Aug-20 02:47 PM no PCBs, but DOP, which is also kinda nasty 26-Aug-20 02:48 PM DOP? Never heard of that 26-Aug-20 02:48 PM dioctyl phthalate 26-Aug-20 02:50 PM oh 26-Aug-20 02:50 PM nasty 26-Aug-20 02:50 PM also: the energy density sucks because they're rated for really high reversal, they're not rated for the kind of duty cycles i'm interested in (they were used to drive an e-beam electron linac and have a peak current only in the 10s of kA range), the inductance is comparatively enormous, the terminal geometry isn't super favorable for stripline integration with my trigatron 26-Aug-20 02:50 PM and there is (or was?) risk of an encroaching wildfire 26-Aug-20 02:50 PM which was, admittedly, the big 'i should put these somewhere else maybe!!' motivator 26-Aug-20 02:51 PM easiest way to get rid of hazmat here is to put it on our craigslist equivalent for free 26-Aug-20 02:52 PM heh 26-Aug-20 02:52 PM ideally it'd be nice if i could establish a working relationship with a local waste-maker-goer-away place, which .. seems like the domain of Businesses more than hobbyists 26-Aug-20 02:56 PM just go make friends with grad students 26-Aug-20 02:57 PM surely there has to be a better answer than making it Someone Else's Problem 26-Aug-20 02:59 PM isn't that how all waste management works? 26-Aug-20 02:59 PM though, giving them away to someone who'd actually find a use for them isn't a bad idea 26-Aug-20 02:59 PM i mean, i guess so, until you get to the guy with the shovel and the incinerator 26-Aug-20 02:59 PM maybe i should just make my own oil burner. i bet the neighbors would love that 26-Aug-20 03:03 PM There is, apparently, one singular vendor that adapts from M30x0.75 to SM1 26-Aug-20 03:03 PM maybe @funranium can give some tipps with disposal? 26-Aug-20 03:03 PM they are an optics-specific machine shop in singapore 26-Aug-20 03:03 PM fun 26-Aug-20 03:03 PM Who? 26-Aug-20 03:03 PM @GigaSquirrel we chatted slightly already, heh 26-Aug-20 03:04 PM "Singapore Optics Shop", I think? 26-Aug-20 03:04 PM good to see I know the right people 26-Aug-20 03:04 PM @qualia does Alameda contract with WM? 26-Aug-20 03:04 PM i think so 26-Aug-20 03:04 PM I think you /should/ be able to arrange for specialized pickup/disposal? 26-Aug-20 03:04 PM it's not eligible for HHW pickup, too heavy 26-Aug-20 03:05 PM oh 26-Aug-20 03:05 PM how big are we talking exactly 26-Aug-20 03:05 PM 120lbs * 2 26-Aug-20 03:05 PM @hedgeberg considering how simple what you need is, anyone with a CNC lathe could make you one in minutes ? 26-Aug-20 03:05 PM even a bad one 26-Aug-20 03:05 PM "large" "oh they mean, like 5-10 pounds maybe" "120 lbs * 2" oh 26-Aug-20 03:05 PM I did not fully appreciate what the issue here was. 26-Aug-20 03:06 PM ah I remember that place 26-Aug-20 03:06 PM I figured it was an issue of electrolyte chemicals 26-Aug-20 03:06 PM bought Si wafers from them before 26-Aug-20 03:06 PM pricey 26-Aug-20 03:06 PM @idmb i dont think a cnc lathe would be able to hand the thread constraints 26-Aug-20 03:06 PM at least not the .5 constraints 26-Aug-20 03:06 PM althought... I do have a screwmaker's lathe... I wonder if I could do this by hand... 26-Aug-20 03:07 PM I didn't know that they customized thread adapters 26-Aug-20 03:07 PM only one way to find out then? 26-Aug-20 03:08 PM lathe is not in the condition for careful work, unfortunately. 26-Aug-20 03:08 PM ah 26-Aug-20 03:08 PM also not only is their site not updated - still uses flash 26-Aug-20 03:08 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-24A65.png 26-Aug-20 03:08 PM wew. 26-Aug-20 03:08 PM You can get these things for a few dollars now 26-Aug-20 03:09 PM yeah it would be $65 SGD before shipping for this adapter. 26-Aug-20 03:09 PM which, no thanks 26-Aug-20 03:09 PM @qualia so what exactly have you looked into for waste disposal? 26-Aug-20 03:09 PM 42mmx0.5mm pitch shouldn't be a problem? 26-Aug-20 03:09 PM it would need to be a pretty nice CNC lathe to achieve that, no? 26-Aug-20 03:09 PM sometimes what puts me off isn't the price of the item itself, cause if I need something and can't make it myself 26-Aug-20 03:09 PM I would order it 26-Aug-20 03:09 PM but what I fear is shipping 26-Aug-20 03:10 PM stepper resolution & threading dont feel like things that would go nicely together 26-Aug-20 03:11 PM Bad CNC mostly comes down to inaccuracies when you have many motions 26-Aug-20 03:11 PM threading is just down to feed rate / jerkiness? 26-Aug-20 03:11 PM so all the backlash doesn't really matter 26-Aug-20 03:13 PM i mean i guess, but then the issue becomes that I don't know anyone with a CNC lathe. if I fixed up my screwmakers lathe, I could maybe change the gear ratio and make this myself though... hrm. 26-Aug-20 03:13 PM but thats like $200 of maintenance for a $10 part. 26-Aug-20 03:17 PM just 3D print something terrible 26-Aug-20 03:22 PM ...maybe it doesnt need to be terrible. could get something hi-res printed by shapeways in an opaque resin. 26-Aug-20 03:25 PM You could 3D print soft inverted vice jaws 26-Aug-20 03:25 PM and probably get a good enough grip to attach whatever mount you want 26-Aug-20 07:36 PM @GigaSquirrel Guess where @qualia started? ;) Sorry it didn't work out. Locally, you next shot is probably Clean Harbors on a chemical amnesty day. Don't hold your breath on one of those happening any time soon. 27-Aug-20 03:16 AM @funranium I've literally never heard of a chemical amnesty day before, is that just a thing for one specific group/region? or is this a national program of some kind? 27-Aug-20 06:52 AM There used t obe something similar here for eWaste 27-Aug-20 06:52 AM To stop people dumping old fridges and TV's on to the side of the roads 27-Aug-20 06:52 AM Now days it's no longer a problem as all stores selling electronics must also accept used electronics. 27-Aug-20 03:59 PM Just like that. Usually sponsored by local fire departments or departments of public health. They’d rather you bring to them to get rid of rather than have it show up in the landfill or discover it during a garage fire response. 27-Aug-20 09:03 PM Quaila what specifically are these? Big caps? Can you be more specific. I may have some suggestions but it depends on exactly what they are. I just went through a complete site cleanup of a tube manufacturing plant in California two years ago and found lots of resources for this kind of thing. 27-Aug-20 09:03 PM @qualia 27-Aug-20 09:03 PM Also Clean Harbors is an option but they are going to roto rooter you about every detail of it and charge you a lot of money, then the guy will swing by in his truck, put a hazmat sticker on each one. Then toss them in the back and take off. Eventually it all just gets dumped in a pit in Nevada. 27-Aug-20 09:03 PM Hazmat electronics handling is unfortunately just an expensive feel good thing but in reality we are just kicking the can down the road. 27-Aug-20 09:03 PM Very little actual proper remediation or recycling gets done unless there is a lot of it and the reclaimables are profitable like in lead acid batteries. I am starting to hear horror stories about iron lithium battery piles the size of small mountains. Nobody is set up to recycle them en mass yet. You can’t just grind them up and floatation mill out the materials and stick them right back into new batteries like lead acid. 27-Aug-20 09:19 PM if it fits in a trash compactor it goes in a trash compactor 27-Aug-20 09:19 PM right? 28-Aug-20 09:42 AM 2 out of the 3 quarter wave plates in my continuum have now fallen out of their mounts 28-Aug-20 09:42 AM Really love it when laser companies don't want to spend $2 more per laser to make reliable components when it costs ~$50k to begin with 28-Aug-20 09:47 AM Again, the power control on my 500k laser is a non-indexed rotation mount 28-Aug-20 09:47 AM I have an up arrow and a down arrow 28-Aug-20 09:47 AM The indexed version of the same Newport mount is only $200 more 28-Aug-20 09:51 AM I'm just pissed off because everything in this laser outside of the design and rod appears to be a piece of crap 28-Aug-20 09:51 AM That, and I don't think it's unreasonable for me to want my optical components to not just fall out of their mounts overnight because you used 3 dabs of loctite 28-Aug-20 10:02 AM the stuff in mine is mostly quite nicely mounted 28-Aug-20 10:02 AM custom machined blocks and everything 28-Aug-20 10:19 AM I feel your pain @Mezmorizor. Like discovering that a minimum of 4 people had blinding injuries because someone deleted a 17 cent tophat over a vertical optic. Pennywise, pound foolish. 28-Aug-20 10:35 AM Jeez. At least these make the laser more safe when they fail because it either ruins the q switch or ruins the pumping which both reduce peak power. 28-Aug-20 10:35 AM Though the penny wise pound foolish is still irritating beyond belief 28-Aug-20 10:35 AM I'm tempted to just torr seal the remaining surviving mount to get it over with at this point 28-Aug-20 10:35 AM And I wish these were machined into a mount. I would even be happy if they didn't use barely acceptable epoxy to glue it in 28-Aug-20 10:35 AM But no 28-Aug-20 10:37 AM gluing optics in place is gross 28-Aug-20 10:37 AM It is 28-Aug-20 10:37 AM But thats the design 28-Aug-20 10:37 AM we have stacks of lenses 28-Aug-20 10:37 AM that are glued into mounts 28-Aug-20 10:38 AM So I gotta do what I gotta do 28-Aug-20 10:38 AM but the mounts are really just so you can handle them 28-Aug-20 10:38 AM you need to put them in other special tilt mounts 28-Aug-20 10:38 AM but we only have four of those 28-Aug-20 10:38 AM despite like 100+ lenses ranging from f= - 50mm to f = 3m, 28-Aug-20 10:39 AM Those type of lenses is how I wish they had designed it 28-Aug-20 10:39 AM But the QWPs are too thin to really have a solid purely mechanical mount 28-Aug-20 10:39 AM and then they used cheap glue 28-Aug-20 10:39 AM I guess I could have the shop make a mount that's more like that 28-Aug-20 10:39 AM But the hole is pretty small and I don't think I've seen off the shelf qwps that would fit 28-Aug-20 10:39 AM Maybe if it turns out I broke it gluing it back in 28-Aug-20 10:44 AM confused 28-Aug-20 10:44 AM QWP can just get clamped in lens tubes? 28-Aug-20 10:44 AM SM1 thread everything ? 28-Aug-20 10:53 AM There are no SM1 threads or lens tubes 28-Aug-20 10:53 AM Which I could modify it to include 28-Aug-20 10:53 AM But it would require modification 28-Aug-20 10:53 AM Lens tube would also be a tight fit on one of the spots 28-Aug-20 10:53 AM There's maybe half a centimeter leeway 28-Aug-20 10:53 AM I guess what I'm really saying is I can see why they rebranded recently 28-Aug-20 11:02 AM What are the mounts like?? 28-Aug-20 11:02 AM send photos 28-Aug-20 11:02 AM you only need like 1cm to use a lens tube to mount a waveplate 28-Aug-20 11:38 AM It's just a circle with a screw to hold the mount in 28-Aug-20 11:38 AM It wouldn't be hard to make some SM1 thread insert to put in the hole and then use a lens mount 28-Aug-20 11:38 AM But I don't see much point when I can epoxy it. Albeit I wish that was their original design 28-Aug-20 11:40 AM this is the correct mount type. 28-Aug-20 11:40 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/0001-sm-EE97A.png 28-Aug-20 11:40 AM this is not: 28-Aug-20 11:40 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/7661-sm-C1A99.png 28-Aug-20 12:07 PM I know exactly what you mean. The issue is that 1, the original design is they glued a qwp into a circular plastic mount, and then they drilled a through hole through the housing where the QWP is. You then hold the mount in with a screw like that second mount holds a lens in. The problem is that it's cramped and it's quite literally a through hole so I would need to make a custom lens mount to make it fit in there. Which isn't a huge deal, I had to make a vacuum lens mount for the VUV, but it's a hell of a lot more expensive+work than just throwing some better epoxy on the mount and adjusting the angle of the QWP by hand because it's going to be wrong now. 28-Aug-20 12:07 PM Wed also have to buy retaining rings because our machine shop refuses to make them unless they're quite large 28-Aug-20 09:13 PM I ended up designing and ordering an adapter for converting from M30x0.75 to RMS on shapeways in SLA resin. More expensive than it needs to be but now I'm curious about whether or not it will work. if anyone wants the design lmk. I'd upload it but its apparently too big. 28-Aug-20 09:13 PM actually wait maybe i can compress it 28-Aug-20 09:13 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/rms_to_30x075-D6428.zip 28-Aug-20 09:13 PM yup 28-Aug-20 09:13 PM there we go. I doubt anyone else will need to make the conversion ever, since this doesn't appear to be a typical adapter, but hey, just in case. 28-Aug-20 09:26 PM this arrived 28-Aug-20 09:26 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20200829_122024-390EB.png 28-Aug-20 09:26 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20200829_122128-232E2.png 28-Aug-20 09:26 PM now time to get a HV probe, measure the negative ion generator supply, etc 28-Aug-20 09:26 PM and finish the high speed amp and MCU circuits 29-Aug-20 12:48 AM hell yeah 29-Aug-20 12:48 AM bit short hv cable 29-Aug-20 12:50 AM yeah 29-Aug-20 12:50 AM I'd probably solder some wire up and heatshrink it myself 29-Aug-20 12:50 AM the wire looks thin though 29-Aug-20 12:50 AM can it actually do a few kV? 29-Aug-20 12:50 AM hmmm 29-Aug-20 12:57 AM it better can 29-Aug-20 12:57 AM esp. with the ptfe sleeve 29-Aug-20 01:11 AM so long as you're not pushing too much current, and the wires are good material, you'll be fine 29-Aug-20 01:11 AM ime most things that use really thick cables are really kinda using them in places where they're not necessary. I'm sure there's more reason to it than I'm thinking of, but like... I'mma be honest, I don't think I've ever really seen an appropriate use for 8 or 10 AWG wire except in things like utility stations. 29-Aug-20 01:16 AM @SleepyOwl Joyce is the pic you posted of this item? https://www.ebay.com/itm/Anode-layer-ion-source-plasma-sputtering-thin-film-deposition/253294719928 29-Aug-20 01:16 AM no 29-Aug-20 01:16 AM it's this 29-Aug-20 01:16 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-B9D00.png 29-Aug-20 01:17 AM Ah, your mention of an ion generator made me think of it 29-Aug-20 01:18 AM Photon is our business 29-Aug-20 01:18 AM because I am using a negative ion generator supply 29-Aug-20 01:18 AM those cheap chinese modules that claim to output -7 kV 29-Aug-20 01:18 AM Saw you talking about them before 29-Aug-20 01:19 AM oh the ones that @qualia played around with like... a year or so ago? 29-Aug-20 01:19 AM yeah 29-Aug-20 01:19 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20200825_174906-0ED3D.png 29-Aug-20 01:20 AM I meant to buy a bunch of those and then promptly forgot but they still look so fun tbh 29-Aug-20 01:20 AM the photocathode doesn't need a lot of current - maximum photocathode current given the the datasheet is 200 pA 29-Aug-20 01:20 AM whats the photon detect for? and what are you driving at? 29-Aug-20 01:20 AM I am working on a Quantum Key Distribution experiment in open air 29-Aug-20 01:21 AM OOH 29-Aug-20 01:21 AM neat. 29-Aug-20 01:21 AM i should get my tek p6015 on my HV modules 29-Aug-20 01:21 AM these things deserve a good measuring 29-Aug-20 01:21 AM the HPDs are to detect photons or quasi single photon beams 29-Aug-20 01:22 AM yeah, that tracks. What does the drive circuitry look like? I'm assuming the signal coming off the sensor looks something like a random-delay impulse train? 29-Aug-20 01:23 AM i have used one of those 7kv negative ion generators on a bench supply to generate bias voltage for corona tube neutron detectors, which are already pretty noisy, but i never really quantified it properly then & could do a lot better now 29-Aug-20 01:23 AM i think so 29-Aug-20 01:24 AM as given by the datasheet 29-Aug-20 01:24 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-5569A.png 29-Aug-20 01:24 AM avalanche diodes are weird 29-Aug-20 01:25 AM yeah 29-Aug-20 01:25 AM I am REALLY considering getting an even faster and higher bandwidth scope to replace my HP 54615B (500 MHz) 29-Aug-20 01:25 AM semiconductor detectors in general always make me a little nervous about like, damage 29-Aug-20 01:26 AM rightfully so tbh 29-Aug-20 01:26 AM ive broken a lot of semiconductor detector elements during testing, mostly by doing stupid stuff, but they are incredibly easy to mess up with 29-Aug-20 01:31 AM yeah 29-Aug-20 01:31 AM @SleepyOwl Joyce are you using pulse detector or sample-and-hold stuff for this setup? 29-Aug-20 01:31 AM or is this more of a "just use a really good, fast ADC" kinda thing 29-Aug-20 01:33 AM I am looking at using an op-amp and a comparator that can hold the output for a while 29-Aug-20 01:33 AM I am looking at just detecting the individual peaks of the signal, etc 29-Aug-20 01:33 AM and then that would be a "count" 29-Aug-20 01:36 AM so, if that's the case, you may want to consider looking at maxim's sample & hold offerings combined with a latching pulse detector. I had some uh... frustrating results in the past due to trying to sample an exceptionally low quality signal, but the pair working in tandem was surprising effective. 29-Aug-20 01:36 AM I'll take a look at that 29-Aug-20 01:41 AM You can stagger them, so that only one pair trips at a time, allowing you to capture some abitrary number of pulses in parallel, When I was working with them I had an fpga for reading the values and then clearing the latches, and all in all it /almost/ worked well enough to read an image off of a monitor using just an antenna. So long as you're not terribly worried about sampling impulse magnitude accurately (i.e. magnitude relative to nearby pulses is sufficient) it should work really well at a pretty good pricepoint 29-Aug-20 01:41 AM my boss had this ill informed idea that you could embed secret hidden qr codes in pictures displayed on a monitor, and then detect single-bit differences with this setup, and all on a very low budget. 29-Aug-20 01:41 AM he was, of course, wrong, the signal was basically at the ambient noise floor even in a lightly shielded lab, but im pretty sure that when I couldn't make his bad idea work is when he decided to not renew my contract. And that's why I don't work for disney anymore. 29-Aug-20 01:46 AM I see 29-Aug-20 01:55 AM anyway long story short is that this may not work for you at all, it definitely isnt a perfect solution, but its probably worth playing with. iirc I could effectively detect pulses down to 1.2 ns wide with some really cheap ICs. Good luck! I hope I'm not being annoying with any of this I just think the experiment sounds really cool 29-Aug-20 02:30 AM nah you're fine haha 29-Aug-20 07:54 AM @SleepyOwl Joyce are you aware of the quantum communication stuff being worked on in Alberta? http://quantumalberta.ca/quantum-technologies/quantum-communication/ 29-Aug-20 07:55 AM No haha 29-Aug-20 07:55 AM and in our case - it's more of a: "Let's see what it takes to even get such a thing implemented without the need for being in a organisation or university, etc - just a means to try and show that you can do experimentation even in fields like Quantum Information Theory without needing too much resources" 29-Aug-20 07:55 AM I don't expect to compete with say, researchers in organizations or publicly funded institutes 29-Aug-20 07:55 AM of course - it would be fun to try and push the limits of such an amateur setup 29-Aug-20 08:01 AM Of course, but you can definitely compete in cost effectiveness if you’re doing things similar 29-Aug-20 08:01 AM As much as we love bringing out wheelbarrows of money, we love not having to do that too... 29-Aug-20 08:02 AM yeah - but we'll see how this all goes 29-Aug-20 08:03 AM I don’t follow it at all but they might have some stuff worth reading for your stuff 29-Aug-20 08:03 AM perhaps! 29-Aug-20 08:03 AM We're also reading other papers, etc to just get a feel of the engineering and physical constraints encountered 29-Aug-20 08:04 AM In my experience the best documentation will be in a relevant thesis 29-Aug-20 08:04 AM Because they can actually put words in those 29-Aug-20 08:05 AM yeah 29-Aug-20 08:05 AM that being said 29-Aug-20 08:05 AM I am supposed to get a website running for documenting all our stuff 29-Aug-20 08:05 AM our circuits, setups, etc 29-Aug-20 08:12 AM Please have a “mistakes” tab 29-Aug-20 08:12 AM Academics refuse 29-Aug-20 08:14 AM Mistakes? That word doesn't exist in our vocabulary 29-Aug-20 08:15 AM I mentally tallied the cost of my mistakes vs savings ideas 29-Aug-20 08:15 AM Still in the green for now... 29-Aug-20 08:15 AM Still amused the only mirror I can use for one part of my pulse shaper 29-Aug-20 08:15 AM Is a discontinued high power dielectric from CVI 29-Aug-20 08:15 AM All the other similar ones seem to burn. 30-Aug-20 01:37 PM my laser is now only outputting ~1.4W 30-Aug-20 01:37 PM Down from specced 13W and 17W actual 30-Aug-20 01:44 PM @idmb oh no. So the question is where is it going? Just weak emission or is something soaking up the beam somewhere and just getting hot? 30-Aug-20 01:44 PM Or weak driver? 30-Aug-20 01:45 PM so it's a chirped pulse amplifier 30-Aug-20 01:45 PM and I'm referring to the output after the pulse compressor 30-Aug-20 01:45 PM Oh. Nevermind. Was thinking CW laser 30-Aug-20 01:46 PM more current? 30-Aug-20 01:46 PM The first amplification stage should bring to ~5-8W, depending on how it's tuned 30-Aug-20 01:46 PM (which is a "multi-pass" type amplifier) 30-Aug-20 01:46 PM and then the second is a single-pass which does the other bunch of power 30-Aug-20 01:47 PM I have never had a chance to use that stuff. That’s like the study of black magic to me! Hahaha 30-Aug-20 01:47 PM Based on it having changed day-to-day 30-Aug-20 01:47 PM it seems like something is slowly burning 30-Aug-20 01:47 PM rather than just being misaligned 30-Aug-20 01:47 PM Oh 30-Aug-20 01:47 PM Yeah you have a serious problem at this point 30-Aug-20 01:47 PM And by the curse of being under warranty 30-Aug-20 01:47 PM I'm not allowed to fix it 30-Aug-20 01:47 PM Won't be long until it's not good enough 30-Aug-20 01:48 PM well it's already impossible to centrifuge with 30-Aug-20 01:48 PM Even though your application is very not demanding 30-Aug-20 01:48 PM but I'm... not using the centrifuge... 30-Aug-20 01:48 PM I'm only using 300mW right now 30-Aug-20 01:48 PM But I would like to be able to use the centrifuge 30-Aug-20 01:48 PM seeing as that is why we bought the laser 30-Aug-20 01:49 PM Well then Warranty away. All it will cost you is time 30-Aug-20 01:50 PM Especially so, they fly techs in to do it. 30-Aug-20 01:57 PM It's why we don't buy the service plan ever tbh 30-Aug-20 01:59 PM I have no clue how expensive it is 30-Aug-20 01:59 PM I just know the PI hates wonky pump lasers 01-Sep-20 01:19 AM hi 01-Sep-20 01:19 AM any goto recommendations for tiny little SPAD? 01-Sep-20 01:23 AM ketek seems to make decent ones 01-Sep-20 01:31 AM ok 01-Sep-20 01:31 AM they also make SiPM 01-Sep-20 01:31 AM found hamamatsu SiPM 3 minutes ago 01-Sep-20 01:32 AM Affordable? :D 01-Sep-20 01:33 AM dunno yet 01-Sep-20 01:42 AM "inquiry completed" 01-Sep-20 01:43 AM good luck :D 01-Sep-20 02:28 AM tnx 01-Sep-20 09:45 PM I didn't know. Huh. 01-Sep-20 09:45 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-A2EBE.png 01-Sep-20 09:45 PM I wonder what's the best way to account for dark count effects, etc 02-Sep-20 08:33 AM I want to try something fun when I get my hands on my HV probe and stuff like that 02-Sep-20 08:33 AM I am assuming that the APD in HPDs are typically biased for geiger mode operation 02-Sep-20 08:33 AM what if I bias it to the linear region? 02-Sep-20 08:35 AM then you'll get feedback on the electron energy 02-Sep-20 08:35 AM which will always be the acceleration voltage 02-Sep-20 08:35 AM give or take a few but that will drown in noise 02-Sep-20 08:35 AM I am thinking that if I want to be able to co-relate the photon intensity - then I should be biasing it to linear mode 02-Sep-20 08:35 AM but this is a HPD with a photocathode 02-Sep-20 08:36 AM what do you mean by Photon intensity? 02-Sep-20 08:36 AM okay - the question in my head is: How can I distinguish my laser source from any other light source that happens to be around the area? 02-Sep-20 08:36 AM especially at such high gains 02-Sep-20 08:38 AM not at all, unless you use a wavelength that is not part of the normal spektrum and a good bandpass, or you modulate your laser with some frequency and look for Signals of only that frequency 02-Sep-20 08:38 AM I am going to 3D print an enclosure and add a narrowband optical filter for a given wavelength of light, but there's still going to be some photons from various sources 02-Sep-20 08:38 AM so I was wondering if I could co-relate based on how bright or dim the source is 02-Sep-20 08:40 AM but brightness is just number of photons 02-Sep-20 08:40 AM that will translate in your Output, either as more Photon counts or more current, depending on how bright and how quick your readout is 02-Sep-20 08:40 AM but iirc you're doing single photon stuff, right? 02-Sep-20 08:41 AM well sorta - maybe not single photon as per se, but a small number of photons, like a few hundred photons 02-Sep-20 08:42 AM you might be able to do something with polarisation 02-Sep-20 08:43 AM well yeah, we are going to be working with detection of polarization, etc 02-Sep-20 08:43 AM ah 02-Sep-20 08:43 AM since we need to measure in two basis of polarization anyway 02-Sep-20 08:43 AM 0, 90 +45, -45 02-Sep-20 08:43 AM I can't think about any other information that a photon carries, only energy, Polarisation and direction 02-Sep-20 08:44 AM phase? 02-Sep-20 08:44 AM well at least if you're looking at light from an EM wave standpoint 02-Sep-20 08:44 AM but how do you Filter that 02-Sep-20 08:44 AM it would have to be phase relative to something 02-Sep-20 08:45 AM yeah 02-Sep-20 08:45 AM I mean I am just saying that light could carry information in terms of phase 02-Sep-20 08:45 AM but in any case 02-Sep-20 08:45 AM fair :D 02-Sep-20 08:46 AM what I am going to do for a start - before all the actual QKD stuff happens 02-Sep-20 08:46 AM qkd? 02-Sep-20 08:46 AM quantum key distribution 02-Sep-20 08:46 AM ah 02-Sep-20 08:46 AM stuff that goes above my head 02-Sep-20 08:46 AM (literally, when you got your laser setup from roof to roof) 02-Sep-20 08:47 AM the first set of experiments would be in actually aligning and correlating the beam 02-Sep-20 08:47 AM so as mentioned a bit of time before 02-Sep-20 08:47 AM I am looking at LoRa based RF comms for this 02-Sep-20 08:47 AM basically transmitter and receiver has RF transceivers that communicate information 02-Sep-20 08:47 AM such as alignment or and time information 02-Sep-20 08:47 AM so if a laser is pulsed from the transmitter, and almost instantly, the receiver detects a pulse 02-Sep-20 08:47 AM it can communicate that back to the transmitter 02-Sep-20 08:47 AM the transmitter can pulse a few more times, and the receiver can try to detect these pulses to verify alignment 02-Sep-20 08:47 AM I still wonder if I am over engineering this 02-Sep-20 08:47 AM but I am thinking it would be useful if amplitude information is sent back also, so that we can adjust our optical output as low as possible, and see at which point the receiver stops detecting anything 02-Sep-20 09:11 AM @SleepyOwl Joyce the statistics of photon counting from a laser vary hugely from other sources 02-Sep-20 09:11 AM So if you’re able to count you can easily identify the laser signal 02-Sep-20 09:11 AM Other thing you can do is lock-in 02-Sep-20 09:11 AM Then just filter at that frequency 02-Sep-20 09:13 AM so I am looking to employ a 520nm laser 02-Sep-20 09:13 AM and thus also, a 520 nm narrow band optical filter for this 02-Sep-20 09:13 AM which I would think would get rid of most of the light from other sources 02-Sep-20 09:13 AM I could use as you say, photon counting statistics of a laser to co-relate my signal 02-Sep-20 09:15 AM isn't 520 basically spot on the peak intensity of sunlight? 02-Sep-20 09:15 AM not exactly 02-Sep-20 09:15 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Combined-plot-of-emission-spectra-04B5B.png 02-Sep-20 09:15 AM but yeah, there will be optical shields and things like that to try and limit sunlight and other incident light sources 02-Sep-20 09:15 AM but based on the spectrum of say, LED lights, etc, it will be a concern especially for night experiments 02-Sep-20 09:19 AM Could u use IR diodes or perhaps a strong blue diode 02-Sep-20 09:19 AM blue diodes yeah 02-Sep-20 09:19 AM I am looking at blue-green spectrum of light because it has the highest transmission in air 02-Sep-20 09:19 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/transmission-37E12.png 02-Sep-20 09:19 AM I am trying to optimize for the best probability of detection by the receiver, so I am accounting for effects of absorption, etc 02-Sep-20 09:45 AM powerful 405nm diodes or even 445-450nm diodes seem good 02-Sep-20 10:26 AM I have two 520nm bandpasses before my PMT, pointed at a 520nm screen, covered with multiple shields, and ambient light is still problematic lol. 02-Sep-20 10:26 AM oof if it has to be 520nm kinda sux cuz powerful 520nm diodes are more expensive 02-Sep-20 10:26 AM powerful blues are cheaper 02-Sep-20 10:26 AM tho u need very good beam quality so thats another consideration 02-Sep-20 10:43 AM I have two 520nm bandpasses before my PMT, pointed at a 520nm screen, covered with multiple shields, and ambient light is still problematic lol. @idmb interesting 02-Sep-20 12:56 PM I'm at a loss on how I can get these dust particles off some of my optics. I've tried duster bulb, canned air, drag and drop with methanol, brush technique with methanol, and even full on wipe, but I still have the hot spots. I don't think there's any real damage to the optics causing it, nothing is visible at least. 02-Sep-20 12:56 PM Any ideas? 02-Sep-20 12:59 PM you can statically charge a balloon 02-Sep-20 01:02 PM Worth a shot 02-Sep-20 04:49 PM did it work? 02-Sep-20 04:58 PM No balloons around. Discovered that the output compensator is actually two optics and not one, and most of the dust was in between them 02-Sep-20 04:58 PM But there's still a hot spot somewhere 02-Sep-20 04:58 PM Probably HR or OC 02-Sep-20 04:58 PM Trying to see if there's any way I can get to them without removing them outright 02-Sep-20 04:58 PM Because if I can not have to align the entire system starting with the OC, that'd be great 02-Sep-20 04:58 PM Could also be pockels cell 02-Sep-20 04:58 PM Or rod 02-Sep-20 04:58 PM All 4 of those things are really hard to get to 02-Sep-20 05:02 PM ahhh 02-Sep-20 05:02 PM Also I have no idea how dust got in the middle of it 02-Sep-20 05:02 PM Because it was pretty sealed 02-Sep-20 05:02 PM But whatever 02-Sep-20 05:02 PM It did 02-Sep-20 05:02 PM isn't it like 40 years old 02-Sep-20 05:02 PM Not this one. It's only like 5 02-Sep-20 05:02 PM The other one is 40 years old 02-Sep-20 05:05 PM Hmm 02-Sep-20 05:05 PM crazy 02-Sep-20 07:22 PM crappy inductor but it will hopefully do the job lol 02-Sep-20 07:22 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/UIY-dh8HgQxnrgpyaBelk9GNLWUYP4fR3cPGzqq9Wm-FE2FA.png 02-Sep-20 07:22 PM its for flashlamp circuit 02-Sep-20 07:24 PM Depending on what you need it for, I've seen worse work 02-Sep-20 07:25 PM ill probably remove some turns because rn its exactly what i need but there will be stray inductance from my crappy caps and wires 02-Sep-20 07:26 PM "just short them" 02-Sep-20 07:26 PM in the photos of the chamber on #swap-meet 02-Sep-20 07:26 PM you can see some RF coils made by winding around bike wheels in the background 02-Sep-20 07:27 PM lol 02-Sep-20 07:27 PM i think it will work for my purpose 02-Sep-20 07:27 PM caps are arriving this thursday 02-Sep-20 07:27 PM so ig tmrw 02-Sep-20 07:27 PM man the week went by fast 02-Sep-20 09:41 PM @funranium really stupid question but... if someone wanted to use a laser to illuminate portrait photography, with a galvo mirror, what kind of power / beam size would you want them to get down to? I feel like even a 1mw red is kinda sketchy? 02-Sep-20 10:47 PM Illuminate in what sense? In general, 1mW at visible wavelengths will keep you out of trouble. 02-Sep-20 10:53 PM Just enough to photograph 03-Sep-20 01:03 PM If you have spot sizes no less than 7mm and CW less than 1mW, you are fine for all visible wavelengths. Technically you are going to do public display of a laser with intentional scanning of the crowd without a variance, which is a no-no in the FDA's books if you're doing this in the United States, but what I just told you is what they want you to achieve. 03-Sep-20 01:10 PM You can also go higher power than that, but it depends on your scanning speed and hooboy you are super duper moving into Variance Land at that point, @idmb. 03-Sep-20 01:12 PM I doubt Canada is grossly different 03-Sep-20 01:12 PM How do stores sell those little balls that blast green lasers all over? 03-Sep-20 01:12 PM Oh 03-Sep-20 01:12 PM Haha audience scanning is allowed without a permit here 03-Sep-20 01:12 PM Weird. 03-Sep-20 01:16 PM Health Canada actually has enforcement powers that the FDA doesn't. Your gov't didn't have a OMG Muh Freedumz!!11!1one1! faction that panicked at the creation of MSHA, OSHA, and the FDA. Health Canada is all of those agencies welded together in one and then given teeth. 03-Sep-20 01:16 PM Kids here smuggle firecrackers from the states, but lasers = fine? 03-Sep-20 01:17 PM caps are here lets goo 03-Sep-20 01:17 PM Audience scanning isn't okay without a variance in America either. 03-Sep-20 01:17 PM NOTE: this doesn't stop people from doing it 03-Sep-20 01:17 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/LN9thOCX3-seVhBY6kH70yzTGxSnkdW9tcYVAyNx3b-26441.png 03-Sep-20 01:17 PM shorted everything before touching it lol 03-Sep-20 01:18 PM Looks like the United States is actually way more aggressive at regulating it? 03-Sep-20 01:19 PM i mean people should not buy laser pointers over 5mW in the US 03-Sep-20 01:19 PM doesnt stop anything 03-Sep-20 01:20 PM Yeah basically everywhere other than the US and France allow it ? 03-Sep-20 01:20 PM Oh apparently the US allows it with permits now 03-Sep-20 01:22 PM We always have. Grew out of laser light shows. Blame/thank Pink Floyd. 03-Sep-20 01:24 PM A lot of stuff says formally they did but they just dismissed most permits 03-Sep-20 01:24 PM Okay next question 03-Sep-20 01:24 PM Why would you want to scan an audience with a laser? 03-Sep-20 01:24 PM I don’t recall ever finding that desirable 03-Sep-20 01:40 PM How often is it actually enforced in the US? Because while this is different, I definitely bought a $5 amazon green laser pointer that clocks in at 80mW after adding an IR filter 03-Sep-20 02:08 PM Your problem is an Amazon/Alibaba/Wish third party gray/black marketeering illegal importation. USPS and FDA have more or less declared defeat in the absence of 30+ years of attempts to get Congress to improve or create legislation to help with this. Taking Customs, merging it with Border Patrol, and then shifting all the budget to guys with guns rather than "I WOULD PREFER TO NOT HAVE COUNTERFEIT DRUGS PLEASE" causes them to declare defeat too. 03-Sep-20 02:08 PM As to why you'd want to scan an audience, umm, art? 03-Sep-20 02:08 PM More seriously, it's the accident consideration of not everyone is the same height. Some people might climb up things. You might have a highly reflective floating pig in the beam path. There's a chance for people to get scanned and they'd like to at least show effort to prevent injury. 03-Sep-20 02:14 PM a focusing floating pig 04-Sep-20 09:02 AM I may be interested in a laser to pierce through ruby/sapphire, for making watch jewels.. it used to be done via steel pins and diamond powder,, which is still an option up till the point I need to make thousands 04-Sep-20 09:12 AM aparently even after the laser they still use stepped steel wire to expand the hole to desired I.D. (or so says my book) 04-Sep-20 12:36 PM Considering one of the amazing things about ruby/sapphire is their laser damage threshold, I'd be surprised if something cheap could cut them? 04-Sep-20 06:18 PM well, cheap is a steel wire and diamond paste 04-Sep-20 06:18 PM but yeah, wasnt sure what can be had for not too much and do an okay job, considering cleanup/enlarging is done after 04-Sep-20 07:17 PM Maybe an ex-surgical YAG but that’s not that easy or cheap 06-Sep-20 08:57 AM I think I might have found a suitable laser for my experiments 06-Sep-20 08:57 AM https://www.aliexpress.com/item/4000149974096.html 06-Sep-20 08:57 AM customizable too 06-Sep-20 08:57 AM with a focusing lens 06-Sep-20 09:00 AM sub 20mW tho 06-Sep-20 09:02 AM can be changed as per request 06-Sep-20 09:02 AM oh so u can get a higher power one? 06-Sep-20 09:02 AM yes 06-Sep-20 09:02 AM what are u thinking of getting 06-Sep-20 09:03 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-93813.png 06-Sep-20 09:03 AM 100 mW 06-Sep-20 09:03 AM how far are u shooting it again? 06-Sep-20 09:03 AM ur gonna want a lotta photons right 06-Sep-20 09:04 AM 1.54 km for a start 06-Sep-20 09:04 AM id go for something quite a bit stronger then 06-Sep-20 09:04 AM best bet is get the diode itself and press it into a module 06-Sep-20 09:04 AM will be cheaper/more adjustable 06-Sep-20 09:05 AM perhaps - but the goal actually is to get down to a quasi single photon source 06-Sep-20 09:05 AM I might use higher powers just for link establishment 06-Sep-20 09:05 AM like ensuring alignment 06-Sep-20 09:06 AM also then u can adjust the lenses better 06-Sep-20 09:06 AM oh ok 06-Sep-20 09:06 AM it makes sense for my QKD stuff 06-Sep-20 09:06 AM because if you have a large stream of photons 06-Sep-20 09:06 AM why can't you just put a beamsplitter and intercept some of the photons as an eavesdropper? 06-Sep-20 09:06 AM the purpose of QKD is to exploit the idea that single photons cannot be split*, and thus ensure that eavesdropping will be detected 06-Sep-20 09:06 AM * I mean sure, you could put a crystal that splits a photon, but that also changes its wavelength, etc 06-Sep-20 09:10 AM my understanding is the cheaper lasers aren't super stable / their power fluctuates a lot ? 06-Sep-20 09:10 AM ¯\_(ツ)_/¯ 06-Sep-20 09:10 AM I don't know 06-Sep-20 09:10 AM I could run it for a while and measure it over time with a laser power meter or something 06-Sep-20 09:12 AM I would assume more rapid oscillations 06-Sep-20 09:12 AM just stuff that makes photon counting... hard and noisy 06-Sep-20 09:13 AM I see 06-Sep-20 09:13 AM that can be measured too I guess 06-Sep-20 09:13 AM since we have the HPDs here and all 06-Sep-20 09:13 AM I am just waiting for my HV probe and other stuff to arrive before I mess with the HPDs 06-Sep-20 09:13 AM wanna make sure that the negative ion generator modules can actually work as a HV supply for them 06-Sep-20 09:13 AM what I could do is build an optical attenuator setup, and measure photon counts with the HPD 06-Sep-20 09:19 AM I'm not sure where the "single" comes from 06-Sep-20 09:23 AM single? 06-Sep-20 09:23 AM I mean with a laser 06-Sep-20 09:23 AM you're not going to get single photons anyhow 06-Sep-20 09:23 AM you can get close enough 06-Sep-20 09:23 AM hence I refer to it, as a quasi single photon source 06-Sep-20 09:23 AM like few hundred photons sort of deal 06-Sep-20 11:39 AM I don't know enough about quantum cryptography to know what the actual requirements are for your light, but tbh I'd be pretty surprised if you could get away anything less than an actively stabilized diode laser/HeNe which is either $$$ or being a pretty substantial laser jock 06-Sep-20 11:39 AM I can confirm that those laser pointers have terrible output though 06-Sep-20 11:39 AM Heavy intensity modulation, rarely single longitudinal mode selection, rarely single transverse mode 06-Sep-20 11:53 AM describe actively stabilized diode laser? 06-Sep-20 11:53 AM I mean they do provide diodes with photodiodes in them upon request, presumably for feedback 06-Sep-20 11:53 AM would that work for stabilization? 06-Sep-20 12:09 PM Feedback of some sort is ultimately the idea, but that's not a question you can just answer in general. Maybe you need frequency stabilization so you rig up a littrow ECDL and use the optogalvanic effect to hold it on some line. Maybe you just need intensity stabilization so you use something to measure power and modulate the current to keep it stable. Maybe you need TEM mode stabilization so you do something that I can't think of off the top of my head, probably having to do with a cavity and some saturable absorber 06-Sep-20 12:18 PM Also does this have to be CW I wonder if a pulsed laser would work better 06-Sep-20 12:31 PM Maybe mode locking, but q-switched lasers never actually reach a steady state so they have pretty unstable output. You probably want to use phase sensitive amplification which would need at the very least a chopper though. 06-Sep-20 01:13 PM Even mode locked fluctuates badly based on pumping. 06-Sep-20 01:13 PM The temp regulation alone ends up costing a few thousand 06-Sep-20 01:19 PM I can believe that 06-Sep-20 01:19 PM No personal experience with modelocked stuff 06-Sep-20 01:19 PM Also q-switched lasers practically speaking have unstable resonators because they're usually used for high power applications 06-Sep-20 01:19 PM Which does bad things to your output quality wise 06-Sep-20 01:19 PM Though that's gotten a lot better in recent years with (I assume mainly) better computing tools 06-Sep-20 01:31 PM lock-in sounds much better than stability 06-Sep-20 07:13 PM I mean it can be pulsed even without q switching or modelocking. 06-Sep-20 07:48 PM Yeah with a chopper 06-Sep-20 08:16 PM or like a pulsed flashlamp pumped laser lel 06-Sep-20 08:16 PM which is kinda the same thing ig 08-Sep-20 09:39 AM feeling pumped 08-Sep-20 09:40 AM now stand between two mirrors and burn something 08-Sep-20 09:44 AM bzzzz 08-Sep-20 09:44 AM today was my first shooting train 08-Sep-20 09:44 AM the guy asked me if I already trained somewhere else 08-Sep-20 09:44 AM it was quite fun 08-Sep-20 09:44 AM didn't tell about gaming 08-Sep-20 09:44 AM but the optics in the center of stereoscopic view is the same as rendered 08-Sep-20 10:04 AM ok not exactly laser related 09-Sep-20 05:45 AM practice shooting, lasers and @funranium s worst nightmare 09-Sep-20 05:45 AM ok, no, he has seen enough that I probably can't even imagine his worst nightmare 09-Sep-20 07:50 AM maybe something with pulsed reactors in the shed 09-Sep-20 10:30 AM Well, that's certainly a thing. Sometimes China's "Do what you like, unless it turns out to be bad afterward and then it was definitely bad all along and you get ++Extra Bonus Prison" safety culture is quite impressive to behold. 09-Sep-20 10:54 AM That's amazing 11-Sep-20 10:14 AM Surprising amount of results when you google "laser tree trimming" including this paper where someone tried it with a CO2 laser in the 1980s https://sci-hub.tw/10.2351/1.5057602 11-Sep-20 10:16 AM Berkeley 11-Sep-20 10:17 AM This is such a terrible idea that I can't believe it was seriously considered 11-Sep-20 10:27 AM it's with lasers 11-Sep-20 10:27 AM mhm seems that beat frequency analysis between two similar lasers is the cheapest way to estimate linewidths in my application 11-Sep-20 10:27 AM "cheap" 11-Sep-20 10:38 AM Lasers sound a lot easier than my idea of putting a saw on a drone, or between two 11-Sep-20 10:38 AM It doesn't seem terrible at all, really. If only the airplanes had a mechanism to be aware (or visa versa). 11-Sep-20 10:43 AM Yeah, linewidths are hard to measure sadly 11-Sep-20 10:43 AM I think a fabry perot interferometer is another decent way thats relatively cheap assuming you're not down to MHz linewidths or below 11-Sep-20 10:43 AM Though I dont know the details of how you actually do that 11-Sep-20 11:33 AM just compress it as hard as you can and measure the transform-limit 11-Sep-20 11:04 PM yeah I want more resolution than a real FP would deliver 11-Sep-20 11:04 PM (I'm using one to check if MHzish) 11-Sep-20 11:04 PM just compress it as hard as you can and measure the transform-limit @idmb ok, borrow me your bench for a sec 13-Sep-20 12:11 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200910_163313-05D76.jpg 13-Sep-20 12:11 PM 60ps nitrogen Laser 13-Sep-20 12:12 PM that isn't the one you already posted pics of, is it? 13-Sep-20 12:12 PM looks very different, but iirc the specs are similar... 13-Sep-20 12:14 PM Nope 13-Sep-20 12:14 PM The project started on thursday 13-Sep-20 12:14 PM This one is diffraction limited 13-Sep-20 12:19 PM Transform limited? 13-Sep-20 12:19 PM What's that 13-Sep-20 12:26 PM Shortest pulse duration a spectrum can give 13-Sep-20 12:31 PM Ah FT-limited 13-Sep-20 12:32 PM Yeah 13-Sep-20 12:32 PM Is that 60ps for n2? 13-Sep-20 07:46 PM all right capacitor bank charging is finally working 13-Sep-20 07:46 PM i think my triggering system needs work tho 14-Sep-20 01:50 PM Is that 60ps for n2? @idmb yes 14-Sep-20 02:09 PM shockingly narrow 14-Sep-20 02:16 PM It is a gas 14-Sep-20 02:16 PM Like, that's more or less the whole reason my entire field does everything in the gas phase 14-Sep-20 02:23 PM I like the crystals 14-Sep-20 02:23 PM they're prettier 14-Sep-20 02:23 PM gemstone lasers 14-Sep-20 02:38 PM Ruby lasers are clearly the best lasers because they're made with rubies 14-Sep-20 02:45 PM That's a totally valid reason. 14-Sep-20 06:07 PM y'all might find this one interesting https://civilpedia.org/p/?pid=282&t=p&h=Greenhouse+Gas+Camera 15-Sep-20 01:57 AM hmmp 15-Sep-20 01:57 AM could it be that hard to build small frequency combs? 15-Sep-20 01:57 AM I mean theoretically it's a simple shaped cavity 15-Sep-20 01:57 AM made out of a solid - transparent enough for the desired wavelengths 15-Sep-20 01:57 AM for the wavelengths of my interrest SiO2 and Al2O3 should be fine 15-Sep-20 01:57 AM and making a frequency comb out of it would only require a low power CO2 laser 15-Sep-20 06:55 AM could it be that hard to build small frequency combs? 15-Sep-20 06:55 AM Yes 15-Sep-20 06:55 AM Save yourself the pain and don't try 15-Sep-20 07:50 AM I mean 15-Sep-20 07:50 AM The apparatus isn’t necessarily huge 15-Sep-20 07:50 AM But the bucket of grad student tears is pretty heavy 15-Sep-20 07:55 AM mhmm 15-Sep-20 07:58 AM Yeah, the thing with frequency combs is that they're "just" ultra stabilized mode locked lasers 15-Sep-20 07:58 AM The problem being that they're "just" ultra stabilized 15-Sep-20 07:59 AM yeah - I simply want such a cavity as a substitute for my current littrow style one 15-Sep-20 08:08 AM but yeah, y should that be easy 15-Sep-20 06:44 PM https://streamable.com/1qwymm Can get it to flash but not super consistent 15-Sep-20 06:44 PM Need to work on the trigger system 15-Sep-20 11:05 PM Trigger system is more reliable now tho could still be better 22-Sep-20 03:13 PM Random cool/relatively easy project idea I'll never get around to doing but still want to see done at some point. FTIR is a common piece of laboratory equipment, but there's not anything unique about IR that means you can't do it with visible light. Just take your light source, put it through a michelson-morey interferometer, and use the output of that to excite your sample which is detected by your CCD detector. You now have a time domain signal that you can fourier transform to get a (UV)-Visible spectrum. The biggest problem will be getting electronics that sample fast enough, but I'm pretty sure that's doable with modern equipment. Cooling might also be an issue if you choose to go with a hefty lightsource like a xenon flashlamp. 22-Sep-20 05:42 PM I should also say that in FT spectroscopy your resolution is determined by the quality of your motion control rather than the bandwidth of your light source 22-Sep-20 11:00 PM I use it for visual 22-Sep-20 11:00 PM but I guess you're talking about pretty low light stuff? 22-Sep-20 11:00 PM I mean using it for characterisation of my lasers 22-Sep-20 11:00 PM what remembers me of reimplementing my crappy python code of it 23-Sep-20 12:11 AM Well, I don't just mean the Michelson-Morey aspect. I mean expanding the concept of an FTIR to other nonstandard wavelength regimes and using it to take some spectrum of something. I just said visible because microwave is both old hat at this point and would require your sample to be put in the gas phase which realistically limits your sample options and adds complexity. That leaves us with visible. Plus, broadband visible light sources are cheap and abundant, and if your light source isn't broadband you don't really gain anything by doing a FT spectrometer over a standard monochromator UV-VIS outside of niche situations. I said Michelson-Morey as your source of a time domain signal because it's a relatively simple optical set up and you can look into the FTIR literature for help with improving your set up/extracting your spectrum, but there are a lot of other options there. It's also a nice project because it's really as good as you want it to be. A good 50/50 beamsplitter is pretty required and you'll need to go commercial for the oscilloscope/whatever else you want to use because the sampling rate requirements are pretty high (haven't actually calculated them myself, but in general these type of systems are limited on this front), but otherwise everything else is pretty whatever you want. Want to use a photodiode as your detector? Sure. Want to buy a hammatsu CCD instead? Why not. Want to machine your own translation stage? Knock yourself out. Want to buy the kind of translation stages they use for the really high precision stuff at NIST? Sure. And while I don't think this is a particularly feasible hobby project because it just has a lot of moving parts, what I would really like to see is to expand it even further to something called "action spectroscopy" where rather than detecting changes in the light beam you detect the effect your light beam had on your sample. Say, the removal of an argon tag. 23-Sep-20 12:11 AM I also almost cursed near the end of that which would have been painful to retype 23-Sep-20 01:45 AM with Morey you mean Morley? 23-Sep-20 01:45 AM not that I mix things up here 23-Sep-20 01:45 AM (I also fck ups all the names very often - so I don't want to judge) 23-Sep-20 10:09 AM Oops, yeah 23-Sep-20 10:09 AM Doing things at 3 AM is not wise 23-Sep-20 06:18 PM Michelson-Moray Eel 26-Sep-20 01:30 PM gah, I hate when you have so many filters that you just have a huge bundle of reflections to deal with 28-Sep-20 01:48 PM @Mezmorizor you don't gain anything using an array/matrix CCD over photodiode though, unless you have bad focus and are trying to collect more signal or something 28-Sep-20 01:48 PM I've got an old FTIR in the garage 28-Sep-20 01:48 PM Never tried using it for real work since it's old and has some goofy massive cable, but plugging it in warms the IR source up to glowing, and the HeNe turns on, and the mirror starts pulsing 28-Sep-20 02:29 PM 1. 3 AM 2. That's really not the point. Yes, detector will probably never be your resolution limiter if you buy a $50 silicon photodiode, but the big point is that it's modular and you could easily want to use the michelson-morley for something that does need an array, and it's not like you can't use the CCD for an FTIR measurement even if it's overkill 28-Sep-20 11:07 PM pulsing mirror 29-Sep-20 07:23 AM i think i'm only going to order from Thorlabs in the future: i didnt realize they include a snack box 29-Sep-20 07:28 AM snack box? 29-Sep-20 07:45 AM they send along a box of snacks with your order 29-Sep-20 07:45 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Qf1XCN3zs5VP9QSgw9QhssZelO9JHhAaoKXSNOwyvp-C65D4.png 29-Sep-20 07:46 AM wow 29-Sep-20 08:05 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-C5B8F.jpg 29-Sep-20 08:05 AM prepped 29-Sep-20 08:05 AM kinda 29-Sep-20 09:00 AM anyone know a good source for goggles at both 1064 nm and 532 nm laser light? 29-Sep-20 09:12 AM i have these: https://www.thorlabs.com/thorproduct.cfm?partnumber=LG10B 29-Sep-20 09:12 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-9A85B.png 29-Sep-20 09:12 AM not the cheapest, but buy-once-cry-once sort of thing (and cry less than blinding myself ) 29-Sep-20 09:16 AM haha 29-Sep-20 09:16 AM is there a goggle that has a high OD across the entire visible spectrum? 29-Sep-20 09:16 AM sticks metal foil on her glasses 29-Sep-20 09:28 AM @polyfractal newport also has photon food 29-Sep-20 09:32 AM TIL! 29-Sep-20 09:32 AM i have mostly bought from Edmunds in the past (go go clearance section), didnt know other vendors had tasty food boxes though 29-Sep-20 09:40 AM thorlabs is quick with a nice website, excellent customer service, and fairly decent quality. newport is slow, with a terrible website, customer service that will make you question your sanity, and excellent quality 29-Sep-20 10:30 AM Wow those boxes of thorlabs snacks haven't changed in more than a decade 29-Sep-20 10:33 AM @SleepyOwl Joyce You can search here for a good pair of glasses depending on your requirement: https://www.lasersafety.com/product-category/eyewear/page/2/?sfilter=1&od_ranged=1&range_0=532&od_0=5&range_1=1064&od_1=5&orderby=price&really_curr_tax=20-product_cat 29-Sep-20 10:33 AM They are pricey but if you're working with high power lasers it's worth it 29-Sep-20 10:33 AM Eagle Pair is the cheaper option, they are CE certified and offer some OD7+ safety glasses at limited wavelengths 29-Sep-20 11:37 AM https://www.youtube.com/watch?v=w3jV58_Vv24 29-Sep-20 07:57 PM PROTIP: don't forget about your Lab Snacks/Photon Food/etc. They go off surprisingly fast and some are kinda old already. The boxes are awfully handy for random storage. 29-Sep-20 11:18 PM yeah - nice storage boxes indeed 29-Sep-20 11:18 PM I use them for gngn optic parts 30-Sep-20 06:40 AM cleaning up from the electroplating stuff and noticed some cracks in one of my test samples with graphite. Fiddled around some more and managed to "machine" some glass by repeatedly painting it with graphite ink and ablating it away 30-Sep-20 06:40 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/PXL_20200930_132927006-A7FA2.jpg 30-Sep-20 06:40 AM super rough surface so not really usable for much imo (microfluidics would suck in that for example), but nifty effect 30-Sep-20 06:24 PM @SleepyOwl Joyce so like https://www.survivallaserusa.com/Eagle_Pair__190-540nm___800-2000nm_Laser_Safety_Goggles/p1667092_7862069.aspx or https://www.survivallaserusa.com/Eagle_Pair__190-540nm___900-1700nm_Laser_Safety_Goggles/p1667092_7862040.aspx 30-Sep-20 06:30 PM @rfs I think @funranium recommended against that brand but I can't remember if that's true 30-Sep-20 06:30 PM I also have two pairs for my co2 laser cutter 30-Sep-20 06:33 PM Ah, don't recall that 30-Sep-20 06:48 PM recommended against? 30-Sep-20 06:48 PM Any reason? @nmz787 30-Sep-20 06:50 PM I can't remember, I guess he will comment later if it was true 30-Sep-20 07:13 PM I don't recall recommending against this specific manufacturer, but rather making absolutely certain that what you're getting are actually laser safety goggles. A remarkable amount of BS lasers on ebay and aliexpress are showing up with "laser safety goggles" that are little more than welding filters. 30-Sep-20 07:13 PM I do recall advising against buying any lasers they sell as being illegally imported and sold garbage. 30-Sep-20 07:15 PM I know that stryopyro (Drake Anthony) has been talking about this brand and has done a destructive test of these brand of goggles 30-Sep-20 07:16 PM That's nice. He isn't Underwriters Laboratories. 30-Sep-20 07:16 PM shhhhh don't say that name around him 30-Sep-20 07:17 PM My opinions of styropyro are particularly dim. 30-Sep-20 07:17 PM oh yeah he isn't UL of course 30-Sep-20 07:17 PM My opinions of styropyro are particularly dim. 30-Sep-20 07:17 PM ¯\_(ツ)_/¯ 30-Sep-20 07:18 PM for good reason. 30-Sep-20 07:19 PM When your name is a watch word for dangerous irresponsibility to the global laser safety community, you don't have fame. You have infamy. 30-Sep-20 07:20 PM Yeah, I know his stuff is dangerous, reckless even. But what am I to say? 30-Sep-20 07:21 PM It is my place to say as a Laser Safety Officer. His videos are used for training purposes around the world on the basis of "DO NOT DO THIS. YOU WILL BE EXPELLED/FIRED IF YOU DO." 30-Sep-20 07:21 PM So far, I've only had to tell one student "That's your warning. Do that again and you will expelled. And your actions will follow you wherever you try to go because they'll want to know why." 30-Sep-20 07:29 PM I think more than half the PIs here have let students put beam alignment crosshairs on doors 30-Sep-20 07:29 PM Half the laser people that is 30-Sep-20 07:29 PM The theoreticians are safer I assume. 30-Sep-20 07:30 PM Ah, wait. I read closer on Survival Lasers' website. "Note: These goggles are for personal use only, not for any commercial use that is regulated by OSHA" Which is to say what they are selling can't be called laser safety goggles. Their use of the CE mark is highly suspicious to the point of possibly being legally actionable. 30-Sep-20 07:31 PM http://www.eaglelaser.cn/En/GoodsView/847.html 30-Sep-20 07:31 PM They do show their CE certificate here 30-Sep-20 07:36 PM Ah, that's why they're cheap. They're no longer saleable under the current EN:207:2017. 30-Sep-20 07:36 PM Hence Survival Lasers slapping the disclaimer on 30-Sep-20 07:37 PM Well is it illegal for them to put the CE mark on their product? 30-Sep-20 07:38 PM Continuing to use it would be in bad faith. 30-Sep-20 07:39 PM These are so commonly used in the hobbyist community that it would be nice to have good test data on them 30-Sep-20 07:39 PM What does a test look like? 30-Sep-20 07:39 PM I’ve got a TOPAS ready to be fired up 30-Sep-20 07:39 PM Allllll the wavelengths 30-Sep-20 07:40 PM I assume you get a laser of the right power intensity under this table, and a sensitive power meter and just fire the laser at the goggles with the power meter behind: https://en.wikipedia.org/wiki/EN_207 30-Sep-20 07:41 PM Pretty much. 30-Sep-20 07:41 PM You also have to run a variety of pulse widths and rep rates to check for temporary or permanent bleaching effects. 30-Sep-20 07:41 PM "DO NOT SHINE A LASER OF ANY POWER AT AIRCRAFT, MOTOR VEHICLES, BOATS OR LAW ENFORCEMENT! THESE ARE CRIMES THAT MAY BE PUNISHABLE BY IMPRISONMENT! WE DO NOT WANT TO HEAR ABOUT YOU ON THE EVENING NEWS! Please do not jeopardize the freedom we all currently enjoy to own and operate lasers legally." [facepalm] 30-Sep-20 07:44 PM So basically get something else then - got it 30-Sep-20 07:44 PM still wants her eyeballs to work for a long time 30-Sep-20 07:44 PM Are you operating with powerful lasers that are that dangerous you need OD7+? 30-Sep-20 07:45 PM Yes 30-Sep-20 07:45 PM Then yeah, go for the laservison products 30-Sep-20 07:45 PM Pretty good price honestly for what they are 30-Sep-20 07:45 PM Even the 100 mW stuff I intend to use for some experiments warrants goggles for me and folks working on it with me 30-Sep-20 07:45 PM I just want to know what I need to look out for 30-Sep-20 07:46 PM @funranium do you ever observe how the spectra physics techs operate when there? 30-Sep-20 07:46 PM cowboys I dare say 30-Sep-20 07:46 PM The fine folks on Survival Lasers appear to be well aware of the fine line that it is perfectly legal to own and use whatever laser you want in America, but perhaps unclear that sales & manufacture are a very different matter. 30-Sep-20 07:46 PM And as a former SP service engineer, I am very well aware @idmb. 30-Sep-20 07:47 PM f 30-Sep-20 07:47 PM How much is their insurance? 30-Sep-20 07:47 PM All I can guess is not enough 30-Sep-20 07:48 PM I make a point to teach my researchers "When the tech is working, you do not remain in the room. No one does. If anyone is injured it will be them alone." I haven't had much argument. 30-Sep-20 07:48 PM The person who sells that stuff to anybody is a close cousin to the guy who does not pay taxes cause in his belief income taxes are illegal and unconstitutional 30-Sep-20 07:49 PM Yes 30-Sep-20 07:49 PM Ah, an interesting difference from “have them teach you so you can do it when it’s out of warranty” 30-Sep-20 07:50 PM i'm not in the optics industry or academia at all, so silly question: do the techs do supremely dangerous things or something? Or just the nature of servicing machines/equipment, that there might be lasers flashing all around the room or something? 30-Sep-20 07:50 PM How do you feel about drilling holes into laser chassis so you can turn knobs with screwdrivers while it’s closed? 30-Sep-20 07:50 PM @polyfractal they’re very cavalier. 30-Sep-20 07:50 PM SP has always had a long reputation that they have perpetuated down the years as rather unsafe laser cowboys. 30-Sep-20 07:50 PM ah 30-Sep-20 07:51 PM It’s mostly accountability and liability around the question when you are in front of the judge the organization can say this person was qualified to be doing this thing. 30-Sep-20 07:51 PM A reputation I can validate having worked with, and yelled at, them. 30-Sep-20 07:51 PM Technically qualified, yes. Callously indifferent to the life and safety of others? Yes. 30-Sep-20 07:52 PM oh boy. i understand the advice to leave the room then 30-Sep-20 07:52 PM I am totally guilty of this kind of manner of operation around the stuff I do. 30-Sep-20 07:53 PM Do it alone in the comfort of your personal lab, no problemo. 30-Sep-20 07:53 PM Do it in a high bay with dozens of other people? No bueno. 30-Sep-20 07:53 PM I have no thoughts about myself smearing leaded solder paste all over for our vibration spec stuff but the thought of one of the assemblers doing it is unthinkable to me. 30-Sep-20 07:57 PM Alright, gotta log off for food. Take home message from earlier stuff: Part of the reason good safety gear is expensive is because the manufacturer paid the money to certify sure it is with reputable testing houses. You can get cheaper stuff that is being sold off label, but then you get to burn the time and effort to validate the things the seller claims but didn't pay for. Or you get to burn an eye. 30-Sep-20 07:58 PM It’s all countability. 30-Sep-20 08:00 PM i bought my first grownup pair of goggles recently and this feeling of dread has lifted that I didnt realize I was carying around (prior owner of one of those Eagle Pair's ). Honestly not that much more expensive, should have done it sooner 30-Sep-20 08:00 PM oh? 30-Sep-20 08:00 PM Although yeah - the Thorlabs stuff that was posted some time back looks good 30-Sep-20 08:02 PM other than the filtering (which I'm assuming is better) fit/finish is much better. very little light leakage around the sides, whereas the cheapo pair had pretty sizable gaps you had to be careful about. 30-Sep-20 08:03 PM the gaps are the problem 30-Sep-20 08:03 PM I need something that would fit over my glasses 30-Sep-20 08:03 PM yes - my eyeballs have issues, but DIY lasik from stray laser reflection isn't something I wanna do 30-Sep-20 08:42 PM The other part of why safety gear is expensive 30-Sep-20 08:42 PM Is because so few people use it that it’s sold in relatively low quantities 30-Sep-20 09:04 PM @SleepyOwl Joyce contacts for laser time? Or a cheap pair or slimmer glasses? 30-Sep-20 09:04 PM I am sure there are slip on goggles that cover the glasses 30-Sep-20 09:04 PM I don't like contacts all that much 30-Sep-20 09:05 PM I don't wear either, so it's hard for me to be too understanding of the issues 30-Sep-20 09:19 PM is almost blind without her glasses 30-Sep-20 10:05 PM @SleepyOwl Joyce The major laser safety eyewear manufacturers definitely make over-the-glasses laser safety eyewear to fit a variety faces. Even people with huge heads and small noses like me. Generally the OTG styles are cheaper that usual too. 30-Sep-20 10:05 PM I see 30-Sep-20 10:18 PM I fairly fond of the filter and eyewear search tool that Laservision has and if you get ahold of the right people they're willing to do custom work for you for weird applications. If you're in Germany, they have a different website to use and pricing. https://www.lasersafety.com/eyewear/ 30-Sep-20 10:18 PM Because Germany is "special" and "deserves all the nice things". 30-Sep-20 10:46 PM doggles 30-Sep-20 10:46 PM https://youtu.be/W-2kBQQZtPU 30-Sep-20 11:29 PM Exactly. All the nice things. 01-Oct-20 12:39 AM I've owned several eagle pair laser glasses over the years and have found them to be as advertised 01-Oct-20 12:39 AM I give them my recommendation 01-Oct-20 12:39 AM At least according to my thorlabs laser power meter, they do what they say on the box 01-Oct-20 04:40 AM oh my god doggles. i thought it was just photoshop at first but they are real 01-Oct-20 04:40 AM any company that makes doggles deserves my money 01-Oct-20 07:09 AM Can we just get proper VR goggles + cameras for laser work already?? 01-Oct-20 07:09 AM For a lab even $2000/pair would be cheaper than stocking all the types we have 01-Oct-20 10:33 AM I will add that one of the surest ways for a company to get an FDA investigation is to be featured in a styropyro video. In that respect, he's doing some public service even if it is unintentional. 01-Oct-20 10:39 AM I wonder if any still see a net return 01-Oct-20 10:46 AM You seem to have a bone to pick with Drake lol 01-Oct-20 10:47 AM is his lasing really the main danger talk, or chemistry, or high voltage stuff? 01-Oct-20 10:48 AM I don't know, a lot of the stuff he does is quite dangerous 01-Oct-20 10:48 AM Like his recent HV tesla coil out of vacuum tube thing 01-Oct-20 10:48 AM Although people know him for lasers and stuff 01-Oct-20 10:50 AM well he has been big on laser forums for like 15 years 01-Oct-20 10:50 AM 13 on laser pointer forums it seems 01-Oct-20 10:51 AM I see 01-Oct-20 10:51 AM what a mess of a community, yech 01-Oct-20 10:52 AM ¯\(ツ)\/¯ 01-Oct-20 11:05 AM Having to teach students “Yes, I know it looked cool. No, it isn’t remotely safe, don’t let me ever find you building/doing something like that here if you value your academic career.” enough times starts to be indicative that, perhaps, someone is not a good influence. 01-Oct-20 11:11 AM there's definitely a difference between showing something dangerous and discussing why/how and safety precautions... and just blowing things up for entertainment. E.g. Ben Krasnow does dangerous things from time to time but describes the dangers and mitigations very coherently. The few things I've seen of Styro's channel, it's just whatever will make for the biggest explosion or laugh factor. which seems to not be a great role model :) There's seems to be a cohort of YTers like that, distressingly (Michael Reeves and friends comes to mind) 01-Oct-20 11:13 AM Yep. 01-Oct-20 11:35 AM He does say not to try anything at home... 01-Oct-20 11:35 AM Explaining detailed safety precautions every video would get old real fast 01-Oct-20 11:44 AM i think it's more that the whole premise of his channel is to create entirely unsafe contraptions and then try to light things on fire with them. 01-Oct-20 11:45 AM Nothing wrong with that imo 01-Oct-20 11:45 AM Tho more educational/longer content would be better which is why I encourage him to look for a different platform 01-Oct-20 11:45 AM Like twitch or something 01-Oct-20 12:27 PM @funranium as a form SP tech, why does our YAG say the trigger frequency should only differ by 10%? we want to run a 50Hz YAG at 10Hz to protect our dye... 01-Oct-20 01:22 PM Off the top of my head, because SP lasers are like highly tuned Italian 1980s sports cars. They work fantastically when everything is EXACTLY positioned as designed; engine lights on fire and accuses your grandmother of being Mussolini if even slightly out of whack. 01-Oct-20 02:15 PM Oh and you can’t get parts unless you know the right guy and they like you. 01-Oct-20 02:25 PM they like us but the feeling is not mutual 01-Oct-20 03:05 PM I credit most of my success as an adult to the thorough disregard for authority figures as a child. 01-Oct-20 03:05 PM Having to teach students “Yes, I know it looked cool. No, it isn’t remotely safe, don’t let... @funranium naturally I do not make a good academic 01-Oct-20 03:08 PM academic, role model... 01-Oct-20 03:10 PM I wouldn't go /that/ far, to suggest respect for authority makes a good role model. Especially when the present authorities are shooting civilians and polluting the planet like crazy. 01-Oct-20 03:11 PM It's not a binary "disregard or respect" though 01-Oct-20 03:11 PM and it can be a "necessary but not sufficient" thing, too. 01-Oct-20 03:39 PM Can we just get proper VR goggles + cameras for laser work already?? @idmb I designed a VR headset and I can help you make this happen but, you will first need to figure out how to convert signals from camera sensors into DisplayPort using (probably) an FPGA. 01-Oct-20 03:39 PM https://glados.aperture.science/index.php/s/BWk3WNXgfEMPkE2 01-Oct-20 03:41 PM I think getting the FOV and latency right 01-Oct-20 03:41 PM is the hard part 01-Oct-20 03:41 PM Both of those are really easy actually. 01-Oct-20 03:42 PM like how do you mount a camera in front of your face such that your vision is natural 01-Oct-20 03:43 PM There are ways to do it using mirror optics. The hard part that no one has done in hardware / fpga yet is the lens transformation, which, is necessary to do in hardware if you want sufficiently low latency for video-pass through goggles. 01-Oct-20 03:43 PM I don't know anything about VHDL or FPGA work in general though, and am too busy with the other parts of this project to make time for it myself. 01-Oct-20 03:45 PM What way with mirror optics? I've never seen anything that looked remotely natural, I believe you that latency is just "throw someone with circuit experience at it" 01-Oct-20 03:46 PM This is the headset my friends and designed, to give you an idea. 01-Oct-20 03:46 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/9_headset-design2_a-4AD3F.png 01-Oct-20 03:46 PM I have some software I wrote to generate even more compact optics but they never got produced as the company sort of folded. (capitalists got greedy and forced a sale) 01-Oct-20 03:50 PM That's intended as some mixed VR, right? 01-Oct-20 03:50 PM Yes but it can be VR with some additional aluminum thickness 01-Oct-20 03:50 PM I worry greatly about depth perception still 01-Oct-20 03:51 PM To get it absolutely perfect you need more than 1 optical surface, or, software reprojection, but, you quickly adapt to a minor difference otherwise. 01-Oct-20 08:29 PM "naturally I do not make a good academic" @adammunich I noticed. 01-Oct-20 08:30 PM When I was a kid my teachers told me to pay attention but I made robots on autocad instead. 02-Oct-20 09:23 AM @adammunich Robots in autocad is a totally marketable skill!!! If you could have shown them five minutes on you tube from now, back then they would have just left you alone. LEGO and erector sets were far more important to future development than the majority of what they would teach in school, baring basics of reading writing math and history which unfortunately only is a small part of current education. 02-Oct-20 09:23 AM I have no kids but have casually monitored what all my nieces and nephews have been learning all the way up and out of high school. It’s shocking. They have so much homework but it’s all presented in the wrong ways. You could condense it so far down and they would have better retention but they bloat the hell out of it until it’s just a constant pile of mush thrown at them. Nobody can learn that way! 02-Oct-20 09:50 AM Almost like many flaws appear in a constantly defunded education system that goes against what people who study education metrics recommend 02-Oct-20 10:29 AM and teaching to pass state/federal test requirements or SAT/ACT 02-Oct-20 10:31 AM it's a problem that's in many educational systems around the world 02-Oct-20 10:31 AM Asia is very prominent in rote learning and memorization for example 02-Oct-20 10:31 AM even in Singapore alone, extra classes, supplementary classes, etc 02-Oct-20 10:31 AM is a billion dollar industry 02-Oct-20 10:31 AM many parents are competitive and want their child to get ahead of others 02-Oct-20 10:53 AM It's almost funny how awful standardized testing has been. Almost. 02-Oct-20 12:02 PM It's crazy how many people, in tech, I know that send their new 6 or 14 week old kids to daycare... And others that can't handle remote schooling. At the same time I know some non tech folks that tried to do a startup in dairy farming and now the husband ended up in trucking... And their kids are doing just fine completely homeschooled (they chose the curriculum, I think from some religious source). 02-Oct-20 12:02 PM It baffles me why multi-degreed engineers apparently can't handle basic k-12 teaching/mentorship/guidance 02-Oct-20 12:02 PM On the other hand, we've had our kid with us 100% of the time since he was born 2.5 years ago, and I'm considering quitting my job completely to stay home with him (albeit with ulterior motives to work on startup sort of projects too). 02-Oct-20 12:02 PM I also screwed around in most of k-12 hating it, didn't finish (dropped out), still doing pretty good. 02-Oct-20 12:02 PM Most of my skills I owe to my parents... Dad having me help him change the truck brakes, mom junkpicking old appliances for me to take apart with a screwdriver, sending me to robot summer camp and c++ classes starting at age 14 02-Oct-20 12:33 PM I certainly wish I didn't have to go through the standardized tests when I was in middle school and high school... It was so exhausting and honestly boring as hell. The standardized tests in Hong Kong required the memorization of question patterns for the most part, and that's just obtained by repeating old tests. I think I did all of the Hong Kong A-level/CSE/DSE tests from 1980 onwards as part of school assignment, and those were 3-hour long tests 02-Oct-20 12:33 PM As a consequence I didn't know how to code or work with CAD until age 17, and definitely felt like I missed out on a lot of things that school life had to offer 02-Oct-20 12:45 PM most people I know who've done the GRE hardcore 02-Oct-20 12:45 PM agreed that the best way to study was just... doing a bunch of previous similar questions 02-Oct-20 12:45 PM rather than understanding anything. speed > understanding 02-Oct-20 01:35 PM My opinion on the subject is, in schools we... 1. Teach kids to not try new things because if they don't understand them, they get bad marks (and their parents beat them at home because of it) 2. Teach kids to not question authority. 3. Teach kids that memorizing stuff without understanding it is more important than understanding it. 4. Teach kids that the way to success is to "hack" the system, since kids who cheat, rarely see punishment. 02-Oct-20 01:37 PM This is probably a subject more suitable in #off-topic-thats-sometimes-on-topic 02-Oct-20 01:37 PM When I was a youngin', people told me to do well in school, but I also read about how bill gates et al were school drop outs and was like, "so how do you explain that?" 02-Oct-20 01:37 PM To get us back on topic, I actually did get the FLIR Phoenix MWIR camera @adammunich 02-Oct-20 01:37 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-C9468.png 02-Oct-20 01:37 PM This was the second one on offer 02-Oct-20 01:38 PM Wow that one on ebay? 02-Oct-20 01:38 PM Yep, the difference was I found the datasheet which actually had good documentation on the ROIC 02-Oct-20 01:38 PM Welp the first thing you should do is open it up and see if the (probably ricor) cryocooler still works. 02-Oct-20 01:38 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/FLIR_ISC9803_Specifications_3-27496.pdf 02-Oct-20 01:39 PM with MWIR cameras cryocooler failure is the most likely death 02-Oct-20 01:39 PM Yeah, that and RE all the pins and power supply voltages to stuff that isn't the ROIC chip 02-Oct-20 01:39 PM The dewar is going to have a thermocouple in it, and the cryocooler most likely, if it is ricor, expects 12VDC 02-Oct-20 01:39 PM if the thermocouple doesn't get to 70 kelvin thats bad news 02-Oct-20 01:40 PM Anyway it would still be a nice learning experience. Given that old Agema IR cameras still have a decent chance of having a working cryocooler, I figured it was worth a bet 02-Oct-20 01:40 PM i managed to get super lucky with all the MWIR cameras I purchased, the problems were all electronic issues not cryocooler 02-Oct-20 01:40 PM Anyway it would still be a nice learning experience. Given that old Agema IR cameras still have a decent chance of having a working cryocooler, I figured it was worth a bet @Mason_Yu these use peltier stacks 02-Oct-20 01:41 PM https://www.eevblog.com/forum/thermal-imaging/agema-thermovision-900-professional-camera-teardown-and-commentary-by-fraser/ 02-Oct-20 01:41 PM Depends on the model 02-Oct-20 01:42 PM I did have one camera with a cooler that would get out of tolerance if it was too hot, but I fixed it permanently with an additional TEC cooling the motor. 02-Oct-20 01:42 PM https://photos.google.com/share/AF1QipP0O5RIUZStGbkBPRQKvljUOdOrEhTu2eJ51S5ZAMAGlBCHrcOhHxMSCXDhD-a3TQ?key=WFh1UElRTFlpZVpQVWVERFBldnNuSkFHM3ctUGFR 02-Oct-20 01:43 PM Hmm we'll have to see after teardown 02-Oct-20 01:43 PM Is posting teardown pics of a very much export restricted item in public okay at all? I've seen it done on the EEVBlog forum by people working with thermal cams of military origins, but not sure if I want to risk it myself 02-Oct-20 01:44 PM So sometimes the coolers are poorly manufactured and will leak out their UHP helium. If that's the case it's possible to fix them but you will need ultra dry He and bake out. 02-Oct-20 01:44 PM I can do that 02-Oct-20 01:44 PM Already have a bottle on order, since I want to recharge my helium compressor 02-Oct-20 01:44 PM @Mason_Yu Maybe technically no but, this is all very old tech and I don't think anyone cares. 02-Oct-20 01:44 PM @Mason_Yu the working pressure for these coolers can be upwards of 20 bar 02-Oct-20 01:45 PM I'm more concerned about mechanical wear 02-Oct-20 01:45 PM Yeah the ricors are ringbaum engines with no lubricant 02-Oct-20 01:45 PM The linear bearing surfaces may have contacted and worn 02-Oct-20 01:45 PM MTBF 10k hr 02-Oct-20 01:46 PM Most of them are contactless seals, even the ones from this era 02-Oct-20 01:46 PM Unlike the FPSC engines, which can have MTBF of 1M Hr. 02-Oct-20 01:46 PM I talked with all the camera guys at photonics west about this, I got the impression that Cryo failures are what keeps their businesses afloat so there's no reason to improve the designs. 02-Oct-20 01:47 PM Although this seems to have come out of a research application, and has been sitting on shelves for years 02-Oct-20 01:47 PM Which may be a good thing, again all depends on what it looks like after tear down 02-Oct-20 01:50 PM I'm not sure flir makes their own InSb sensors 02-Oct-20 01:50 PM I think most of them are actually from Lynred 02-Oct-20 01:50 PM They do, at least Indigo Systems did 02-Oct-20 01:50 PM They still offer custom detector design and ROIC engineering services 02-Oct-20 01:52 PM https://www.youtube.com/watch?v=E0UKDZ_fW0E&feature=emb_title 02-Oct-20 01:52 PM This was with a 4.26um notch filter 02-Oct-20 01:52 PM And to achieve the required secrecy and control of their customers I think they must make some of their own detectors 02-Oct-20 01:52 PM Yeah really neat stuff 02-Oct-20 01:52 PM So you do have dead pixels on your camera? 02-Oct-20 01:53 PM No, but, when you turn up the gain on these cameras you max out some of the pixels either hot or dark. 02-Oct-20 01:53 PM The uniformity of InSb sensors is really poor 02-Oct-20 01:55 PM Pixel-to-pixel crosstalk is significant too at a small pixel size. I'm actually concerned because the one spec on this camera that doesn't match the baseline modern research MWIR cameras is the pixel-to-pixel crosstalk 02-Oct-20 01:55 PM 25 micron pitch is very small for early 2000s standards of InSb microbolometer 02-Oct-20 01:57 PM Well fundamentally you run into uncertainty limits really fast since the wavelength is 5um 02-Oct-20 01:58 PM Yeah so that's the problem with these "small" form-factor detectors, they are noiser and have more crosstalk 02-Oct-20 01:58 PM I think my camera pitch is 30um 02-Oct-20 01:58 PM And this is like the 1st or 2nd gen 25 um pitch detectors by Indigo systems 02-Oct-20 01:59 PM Personally I have had less issue with crosstalk than I have had with low dynamic range 02-Oct-20 01:59 PM When you use a notch filter it really goes away 02-Oct-20 02:00 PM Your camera has 14 bits dynamic range? 02-Oct-20 02:00 PM Yes but you throw away 10 of those bits when looking at a narrow band and cranking the gain up to compensate. 02-Oct-20 02:00 PM Unless you have a crazy amount of backlighting 02-Oct-20 02:00 PM There's just not many uW to go around at 4.26um 02-Oct-20 02:02 PM Yeah that makes sense. The lens make a big difference too of course. 02-Oct-20 02:03 PM Almost every camera I've seen has an in-dewar f/4 aperture stop 02-Oct-20 02:03 PM The lens that's on the camera I bought is aftermarket at F/2.3 02-Oct-20 02:03 PM So it should be better in terms of sensitivity? 02-Oct-20 02:03 PM The dewar likely still has an f/4 aperture stop 02-Oct-20 02:03 PM I think the only way around it is to get a telecentric lens setup to jam more light through the dewar stop than normal. 02-Oct-20 02:05 PM Sounds like an impossible thing to find/make with a limited budget 02-Oct-20 02:06 PM You can use mirrors and polyethylene actually, both work with MWIR 02-Oct-20 02:06 PM I thought they both attenuate too much and you'd be doing more harm than good 02-Oct-20 02:07 PM Nah mirror lens should work very well 02-Oct-20 02:07 PM I wanted to try a large objective f/4 mirror lens on my camera but haven't gotten to it yet 02-Oct-20 02:07 PM I think it would work very well and be much brighter than the Ge lens 02-Oct-20 02:07 PM example 02-Oct-20 02:07 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/4364029433_f649a171e3-55461.png 02-Oct-20 02:07 PM The transmittance of Ge + AR coating is less than the reflectivity of aluminum first surface mirrors 02-Oct-20 02:14 PM Definitely let us know your results when you get around to do the conversion! This sounds like a really economic way to reduce noise 02-Oct-20 02:15 PM The glass window of these lenses won't do though, it will need to be replaced by some other supporting structure like Si, or more realistically, some thin steel poles 03-Oct-20 01:42 AM is that a maksutov? 03-Oct-20 03:17 PM I think so yes 03-Oct-20 04:40 PM @adammunich nice greenhouse gas camera page! 03-Oct-20 04:40 PM @SleepyOwl Joyce https://www.nature.com/articles/s41567-020-1031-5 03-Oct-20 04:46 PM oh wow 03-Oct-20 04:46 PM I'll have to give this paper a read later 03-Oct-20 04:47 PM @adammunich nice greenhouse gas camera page! @samy it's a really cool field that's surprisingly unexplored 03-Oct-20 04:47 PM I feel like there's a lot of low hanging fruit to grab in the world of gas sensing 03-Oct-20 05:02 PM @adammunich interesting...other areas in particular you think would be neat? 03-Oct-20 05:07 PM other areas? 03-Oct-20 06:46 PM other low-hanging fruit besides camera 03-Oct-20 07:50 PM Oh, in STEM in general? 03-Oct-20 07:50 PM Tons of stuff! People tend to turn a blind eye to everyday problems, and there's a lot of opportunity in solving them. 03-Oct-20 07:50 PM How do you reliably turn on an irrigation valve on in a cornfield, and make sure it actually turned on? How do you monitor whether or not an industrial machine is ready to fail? (hint, microphones). Water scarcity is still not a solved issue. How can you provide clean water to the billion+ people who don't have it? 03-Oct-20 07:50 PM How do you recycle lithium batteries? How do we make soil biomes that fix their own nitrogen? How can we make low-field MRI inexpensive? 03-Oct-20 07:50 PM And one of the most important unaddressed issues: how do we make concrete without greenhouse gas emissions? Something like 8% of all the world's CO2 emissions is from concrete production alone. How do we make trans-oceanic ships use less energy? How do we increase the service life of ship hull coatings so that dry-docking is not necessary every 10 years? 03-Oct-20 07:50 PM How do we make reliable sodium iron phosphate batteries? How can you automate rust removal? How can we protect seawalls and pier pilings from corrosion? How can we replace bisphenol in epoxy, with something more bio-friendly? 03-Oct-20 07:50 PM There's so many huge opportunities like this in STEM that don't get the kind of attention graphene does, but are real problems that if solved, would make not only good academic advancements, but good businesses as well. 03-Oct-20 08:41 PM I think he meant in gas sensing but is equally interested in the rest haha 03-Oct-20 08:46 PM I think he meant in gas sensing but is equally interested in the rest haha @idmb In gas sensing in particular, there are major losses in city gas pipelines, sometimes in excess of 30%. No one knows where this gas ends up. We also do not have a way to detect when methane flares go out and, the standard practice is to notice it months later, and kick a flaming ball of paper from the ground up to the flare to re-light it. 03-Oct-20 08:54 PM In my lab I think about 50% of our 6 orders helium consumption is leaks, but it’s cheap enough and slow enough... blech 03-Oct-20 08:54 PM helium sensors are super easy 03-Oct-20 08:54 PM mems oscillators are very sensitive to He 03-Oct-20 08:56 PM yeah lots of acoustic techniques for helium leak detection too 03-Oct-20 09:12 PM I mean we have a leak detector, somewhere 04-Oct-20 01:13 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20201004_011151-78973.jpg 04-Oct-20 01:13 AM I was just thinking this has most of the makings of a 70 kelvin digital camera 04-Oct-20 01:13 AM With some large format sensor 04-Oct-20 01:13 AM Could bolt a viewport on the front flange and then some electrical feedthru on the back 04-Oct-20 01:13 AM Although I don't recognize what the back actually is 04-Oct-20 01:13 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20201004_011501-50AE4.jpg 04-Oct-20 01:13 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20201004_011508-CE83F.jpg 04-Oct-20 01:13 AM It's almost KF but not quite, it's milled out 04-Oct-20 01:20 AM custom seal for an o-ring, pretty sure 04-Oct-20 01:23 AM An array of consumer cmos sensors could probably work though I worry the power dissipation of the FPGA needed to merge the image would be much, probably needs to be a separate PCB if the sensors are to stay cool 04-Oct-20 01:23 AM If an o ring fits in there that might be alright actually 05-Oct-20 07:03 AM I would like to know where can you find so many Stirling cryocoolers 05-Oct-20 07:03 AM They seem to be a consumable item, and due to their rarity, it would be nice to have more documentation on common failure modes that can be repaired, and the method to repair them. 05-Oct-20 12:26 PM when i saw a bunch available I nabbed them 05-Oct-20 12:26 PM the FPSC ones aren't consumable though, they have a verrrry long mtbf 05-Oct-20 12:26 PM the ringbaum ones are quick to die though 05-Oct-20 02:19 PM @Mason_Yu so I don't know anybody who is still making free piston coolers that can go down to ln2 temperatures, except for SunPower. But there are a couple of ones that more recently showed up that are rated for -100 C. 05-Oct-20 02:19 PM Twinbird.co.jp and rigid HVAC both make them 05-Oct-20 02:19 PM I have the twinbird and it's good, been running for 2 years straight with no issue. Haven't tried the rigid HVAC one yet. 06-Oct-20 10:56 AM After catching an intruder on a rural property with security cameras, the idea of a telephoto lens with an IR laser for illumination sure would be tempting if it weren’t dangerous 06-Oct-20 12:06 PM @idmb you live rural, or have a vacation property? 06-Oct-20 12:25 PM parental rural 06-Oct-20 01:49 PM tempting if it weren’t dangerous @idmb I know a guy who got a $50mn contract to sell these to Uncle Sam 06-Oct-20 02:18 PM that probably makes it harder for him to use it for personal use lol 06-Oct-20 02:39 PM its not totally invisible 06-Oct-20 02:39 PM 808nm 06-Oct-20 02:39 PM a totally invisible one would be dope a.f. tho 06-Oct-20 02:39 PM 10W CO2 laser would make a perfect illuminator for LWIR 06-Oct-20 02:39 PM and be eye safe as well 06-Oct-20 02:40 PM when you have enough of it 808nm is very visible 06-Oct-20 02:40 PM yes their illuminator is visible ha 06-Oct-20 02:41 PM My main laser is a paltry 17W... of 800nm 1Khz 120fs pulses 06-Oct-20 02:41 PM It's very bright. 06-Oct-20 02:53 PM a CW co2 laser spread out like a flashlight though should be perfectly fine for the eyes after only a few meters 06-Oct-20 02:56 PM To get anywhere near close to something legal you'd have to start with that intensity though, can't have it be "it's only that intense where people are supposed to get hit" 06-Oct-20 03:32 PM To use it the United States in that manner would still require an FDA variance for public display, which they dislike giving for near-IR applications in particular. HealthCanada is no kinder. Don't. 06-Oct-20 03:36 PM Is kind of funny to have castle law places with guns 06-Oct-20 03:36 PM but laser surveillance no bueno 06-Oct-20 03:36 PM Surveillance is passive. Laser illumination is not. 06-Oct-20 03:37 PM Yeah I just meant "expected injury" being legal vs "possible injury" being not 06-Oct-20 03:37 PM lasers are a fancy modern thing 06-Oct-20 03:39 PM As an example, Geneva Conventions require you to be trying to kill AT ALL TIMES and then tries to control how you do that. Blinding has to be an accidental side effect, not purposeful. Hence the Protocols on Blinding Weapons that irritating as hell colonels in Pensacola keep trying to get us to break. 06-Oct-20 03:40 PM where is the EMP / LASER cutoff? 06-Oct-20 03:41 PM Oop! EMP! Drink! 06-Oct-20 03:42 PM instead of a laser for IR camera illumination just have a really hot rock and some filters 06-Oct-20 03:43 PM Help yourself. Incoherent sources are much less controlled. Also quite a bit harder to hurt yourself with. 06-Oct-20 03:44 PM I think that becomes untrue when you start talking about illuminating something 100s of metres away using only invisible light 06-Oct-20 07:56 PM https://www.youtube.com/watch?v=h53PCmEMAGo 06-Oct-20 07:56 PM This guy never disappoints 06-Oct-20 08:27 PM I don't think that's necessarily true as long as the intensity at the exit aperture is lower than the eye damage threshold 06-Oct-20 08:27 PM Which for a 10W co2 laser across a 100mm aperture, would be the case 06-Oct-20 08:37 PM ~130mW cm^2 06-Oct-20 08:37 PM (of course that's a lot for NIR but FIR can't be focused by the eye) 07-Oct-20 12:26 AM http://www.brettpeabody.com/#2949 07-Oct-20 12:58 AM I'm pretty into it 07-Oct-20 12:58 AM I wanna see an LED one 07-Oct-20 07:04 AM In order to get the FDA variance to do that, you will indeed need to prove it is eye safe at any point accessible by the public. If you just build it and slap it up there, you now have a surveillance system that you can’t admit you have nor can you use anything from without admitting your own crime. There are much easier and legal non-laser ways to get near-IR illumination of a space. 07-Oct-20 07:08 AM can't you just put it on a very tall pole? 07-Oct-20 07:10 AM I was about to ask the same 07-Oct-20 07:10 AM question 07-Oct-20 07:17 AM That is a way to help achieve that which you would outline in your variance request. In short, keep your lasers indoors. 07-Oct-20 08:27 AM @funranium fun fact, rental-tenancy claims in BC do not have standards for the legality of evidence. 07-Oct-20 08:27 AM it's a one-party consent to record place, so it's not an issue for the most obvious thing, but if it was two-party you could still illegally record people and use that in court 07-Oct-20 09:01 AM The crime isn’t the recording. 07-Oct-20 09:04 AM Oh I didn’t mean in relevance 07-Oct-20 09:04 AM Beyond both being recording related 07-Oct-20 11:23 AM How do laser rangefinders get away with it? 07-Oct-20 11:23 AM Nikon sell 905nm Class 1M lasers 07-Oct-20 11:23 AM Class 1 laser product, power output not exceeding .0975 milliwats. 07-Oct-20 11:23 AM I wonder how bright that would be with just a basic APS-C DSLR with the IR filter removed and a 400mm lens at like 200m. 07-Oct-20 11:23 AM And a high-pass filter of course 07-Oct-20 12:16 PM @funranium are you in canada? Most United States judges I'm aware of would not be able to make such a judgment, lasers are entirely outside their circle of competency 07-Oct-20 12:20 PM Judges rule on a lot of things outside their areas of competency...which is far from ideal but rarely seems to stop that. The worst examples are when there is nobody involved who is competent in the subject matter and the best examples are when they bring in competent experts to advise the court 07-Oct-20 01:04 PM There is a judge in SF who is very good at doing that and handles a lot of technology cases 07-Oct-20 01:04 PM For your run-of-the-mill trespassing case though I don't really see how that would ever happen 07-Oct-20 01:07 PM lets be clear I don't want to go make a crazy laser-lit security camera 07-Oct-20 01:07 PM I just think it would be neat if you could buy one 07-Oct-20 01:08 PM A while ago while I was photographing some of the riots in oakland some people tried lasering my face 07-Oct-20 01:08 PM Little did they expect I had laser goggles 07-Oct-20 01:09 PM Retroreflectors seem like they would be fun in that situation of malicious lasing 07-Oct-20 01:09 PM I was worried about my DSLR 07-Oct-20 01:09 PM Retroreflectors seem like they would be fun in that situation of malicious lasing @LRM ooooooh 07-Oct-20 01:09 PM bit violent eh 07-Oct-20 01:09 PM The proper answer here is hidden cameras 07-Oct-20 01:10 PM I evaporated aluminum onto an SLA printed corner reflector panel and was surprised how well it worked... 07-Oct-20 01:10 PM Unfortunately FDM layer lines cause too much scattering to use your average 3d printer 07-Oct-20 01:10 PM At least not on the scale my friend wanted to test 07-Oct-20 01:11 PM I feel bad I bought a form labs and did almost nothing with it 07-Oct-20 01:11 PM 3d printers are a trap 07-Oct-20 01:12 PM lasercutters are the opposite though 07-Oct-20 01:13 PM I use my FDM a ton and am glad I never got an SLA myself 07-Oct-20 01:13 PM if you have an easy setup to use one, you just make junk constantly 07-Oct-20 01:13 PM I bought one of those 10 years ago and I used it almost daily until I didn't anymore... 07-Oct-20 01:13 PM Now it sits at our hacker space which is unfortunately kind of closed due to the pandemic 07-Oct-20 01:13 PM pandemic means nobody else is ever using our laser cutter 07-Oct-20 01:13 PM or mills or lathes, not that they were ever very busy 07-Oct-20 01:15 PM Yeah my worry is that since the SF Bay area is run by a whole bunch of capitalists, that place and a lot of the others are going to end up folding. 07-Oct-20 01:15 PM Meantime to eviction around here seems to be less than 5 years. 07-Oct-20 01:16 PM instructables HQ still there? 07-Oct-20 01:16 PM I visited ages ago 07-Oct-20 01:16 PM You mean Autodesk's marketing department? 07-Oct-20 01:17 PM Yeah 07-Oct-20 01:17 PM cool place back in the day 07-Oct-20 01:17 PM The only way to survive here is to be a socialist and hang out with the socialists, otherwise it's a really brutal existence. 07-Oct-20 01:17 PM Tech companies will toss you aside the moment you're no longer useful to their VC narrative, and you'll have no sympathy from your landlord lol. 07-Oct-20 01:19 PM just inherit a trust fund 07-Oct-20 01:19 PM then you can be whatever 07-Oct-20 01:19 PM One of my friends did that and what do you know he's a (paper) billionaire now. 07-Oct-20 01:21 PM ez 09-Oct-20 02:28 PM i was thinking last night about whether or not I should sacrifice the stirling cooler on one of my cameras to use the InSb sensor for experiments 09-Oct-20 02:28 PM What? 09-Oct-20 02:28 PM No, not the cooler 09-Oct-20 02:28 PM But if you do, please do a tear down 09-Oct-20 02:29 PM unfortunately they glue the sensor to the cooler cold head, so there is no alternative. you must destroy the cooler with diamond saw to preserve the integrity of the sensor and its wire bonds 09-Oct-20 02:29 PM you could remove the regenerator etc and be left with a hollow tube, and sensor mounted on it 09-Oct-20 02:30 PM Is it a split cooler? Like the one on the Indigo systems camera I posted pics of in #show-and-tell ? 09-Oct-20 02:30 PM then introduce your own cooling 09-Oct-20 02:30 PM Ah yes 09-Oct-20 02:30 PM ringbaum cooler 09-Oct-20 02:30 PM i have one camera that has a cooler that is out of tolerance, if it fails maybe I will do this 09-Oct-20 02:30 PM I could put the sensor into a vacuum chamber and remove its cryostat 09-Oct-20 02:30 PM to get a lot more light onto it than normally 09-Oct-20 02:30 PM make a very sensitive camera the likes of which you cannot buy right now 09-Oct-20 02:31 PM Almost every pixel would be close to photon counting no? 09-Oct-20 02:31 PM They are already basically counting electrons on the latest cryogenic QWIPs 09-Oct-20 02:34 PM Almost every pixel would be close to photon counting no? @Mason_Yu how do you mean? 09-Oct-20 02:34 PM presumably they have a maximum well size like any other photodiode 09-Oct-20 02:34 PM I don't know how large it is 09-Oct-20 02:34 PM the question I don't have an answer to yet is, would this experiment actually help improve dynamic range or not 09-Oct-20 02:38 PM The amount of charge accumulated in the well would be such that you could count how many photons hit the pixel when you read it after integration. Modern InSb are already essentially counting photons in IR, in visible it should be still possible 09-Oct-20 02:39 PM oh yeah, well, this is an InSb sensor 09-Oct-20 02:39 PM the problem I keep encountering with using it for gas sensing is there is just not enough natural light whe you chose a narrow passband 09-Oct-20 02:39 PM I really want to figure out how to make a hollywood quality gas camera 09-Oct-20 02:39 PM so we can go point it at the chevron refinery in richmond and piss off some polluters 09-Oct-20 02:40 PM Don't they use uncooled microbolometers in commercial gas sensing IR cameras? 09-Oct-20 02:40 PM as far as I know, no. they use InSb or the new HOT sensors. 09-Oct-20 02:40 PM With much lower sensitivity 09-Oct-20 02:40 PM https://www.youtube.com/watch?v=4prazMVylRs&ab_channel=FLIRSystems%2CInc. 09-Oct-20 02:41 PM i'm pretty sure that is a HOT sensor 09-Oct-20 02:41 PM ~150 kelvin 09-Oct-20 02:41 PM Ah yes, still InSb 09-Oct-20 02:41 PM Pretty good packaging for them to get everything in such a small camera 09-Oct-20 02:41 PM https://www.flir.com/products/gf77a/ 09-Oct-20 02:41 PM There's this though 09-Oct-20 02:41 PM But only methane 09-Oct-20 02:44 PM So i think you can actually use uBolometers for this purpose but the ones that are built now are not optimized 09-Oct-20 02:44 PM they need to have smaller pixel sizes to be resonant at the 3-4 um band 09-Oct-20 02:44 PM they are presently made to be resonant at the 10um band 09-Oct-20 02:44 PM now that said, i have never cooled one of the 10um ones and maybe that would help it a lot 09-Oct-20 02:44 PM but i do know that most 10um bolometers have a low pass filter on the dewar, which would need to be removed 09-Oct-20 02:46 PM Cooling is definitely needed just to get the sensitivity too 09-Oct-20 02:46 PM And careful filtering 09-Oct-20 02:46 PM I'm pretty sure that the Indigo Systems camera uses this cryocooler: https://www.cobhammissionsystems.com/tactical-control-systems/cryogenic-cooling-systems/cryogenic-coolers-and-controllers/lc1056-linear-cryocooler-13w/docview/ 09-Oct-20 02:46 PM 8K hour MTTF, hopefully it does last longer and hasn't leaked much helium, I don't want to refill it although it looks like it is designed to be refillable 09-Oct-20 02:53 PM man they always suck 09-Oct-20 02:53 PM the FPSC i have has an MTTF of 107 years 09-Oct-20 02:53 PM some of the sunpower ones have an MTTF of 15 years 09-Oct-20 02:53 PM and yet everyone in the camera industry uses these really bad ones instead 09-Oct-20 02:55 PM Well the military requirement may make that number much lower 09-Oct-20 02:55 PM This is a FPSC though right? 09-Oct-20 02:56 PM the military often does not know that better is possible 09-Oct-20 02:56 PM This is a FPSC though right? @Mason_Yu it is but it doesnt have the moving parts centered by leaf springs like the sunpower and STI ones do 09-Oct-20 02:56 PM so they sandpaper themselves to death 09-Oct-20 02:59 PM Ah well if the pressure is still there, hopefully the non-contact bearing is actually working. Looks like these coolers are tested on the assumption they are to be used in environments with severe vibration and physical shock, so that might be the reason for the lower specified MTTF 09-Oct-20 02:59 PM https://www.sunpowerinc.com/products/stirling-cryocoolers/cryotel-cryocoolers/mt MTTF 22 years 09-Oct-20 03:00 PM But it's not tested to go on targeting pods of military jets 09-Oct-20 03:00 PM People like to complain about helium leaking out but I have not had any of the cyro coolers I bought suffer this problem, seems to be they more often suffer mechanical issues. 09-Oct-20 03:01 PM I'd bet if the cooler is shaken and moved a lot, the MTTF will still not be 22 years 09-Oct-20 03:01 PM I actually have one of these but not the driver for it, I have been unable to get it working https://www.sunpowerinc.com/products/stirling-cryocoolers/cryotel-cryocoolers/ds-mini 09-Oct-20 03:01 PM it has 2 voice coils inside with different impedances 09-Oct-20 03:01 PM there's probably some magic amplitude and phase combination I have not sorted out yet 09-Oct-20 03:04 PM I guess this is the Stirling that Ortec uses to cool their HPGe detectors 09-Oct-20 03:04 PM https://www.ortec-online.com/products/radiation-detectors/germanium-hpge-radiation-detectors/detector-cooling/ics 09-Oct-20 03:12 PM The cooler in my camera still hums along nicely, so I have no reason to believe anything is wrong inside. They didn't label any of the ROIC pinouts though, it will be fun to trace that on what appears to be at least a 6 layer digitizer board 09-Oct-20 03:22 PM oh boi 09-Oct-20 03:22 PM ya that will be a mess 09-Oct-20 03:22 PM but solid chance there is an analog video output somewhere 09-Oct-20 03:22 PM No, unfortunately only serial data communication from this board 09-Oct-20 03:22 PM No DACs anywhere 09-Oct-20 03:22 PM It has two of the CY8B923 HOTLink transmitters on it: https://static6.arrow.com/aropdfconversion/6b5dcb3f766d3239905fbef183b1094774651407/cy7b923_8.pdf 09-Oct-20 03:22 PM But no data from those chips 09-Oct-20 03:39 PM Sounds like I need to make an interposer board to adapt to the rigid flex cable from the ROIC. I can't probe the underside of the digitizer board as it is because the rigid flex cable is so short 09-Oct-20 07:23 PM Doing low-level video capture is outside my wheelhouse. :-/ 09-Oct-20 07:23 PM I do know that the stm32f4 has a nice parallel video interface for cmos sensors 09-Oct-20 07:23 PM But looks like you're going to need some kind of line driver and read out amplifier as the sensor is unlikely to have those built in? 09-Oct-20 09:09 PM That's what the ROIC is 09-Oct-20 09:09 PM It has the amplifiers and buffers for reading out the pixels, then framing the data for external ADCs. It contains DACs for biasing the detector too 09-Oct-20 09:09 PM AFAIK all InSb sensors basically have a similar chip bonded directly to the sensor die 09-Oct-20 09:09 PM https://www.flir.com/browse/camera-cores-amp-components/roics/ 09-Oct-20 09:09 PM A list of FLIR's active ROICs, mine uses the ISC9803 12-Oct-20 11:28 AM Had an interesting offer from a vendor. If you’re at learning institution and you feel like you might not have the best selection of laser safety eyewear, or at least not the best variety of frames to fit your face, NOIR is willing to drop a fit kit on your safety folks for free so you can go in to try things on. As I’ve learned the hard way, not every university’s safety folks seem to have the bandwidth to go out and seek help to improve their laser support. If you’d like me to give your institution a swift kick for you to get this, I’m happy to help. 12-Oct-20 11:31 AM fit kit? 12-Oct-20 11:46 AM A set of all the frames they make so you can see what fits best and you’d like to put your expensive laser filters into. 12-Oct-20 11:54 AM Is individualized pairs 12-Oct-20 11:54 AM A normal thing down there? 12-Oct-20 12:34 PM Yes. Yes it is. Because if the eyewear is uncomfortable, you are very unlikely to wear them. If it doesn’t fit right, gapping is a safety issue and we want to catch that early. 12-Oct-20 12:42 PM I think the fact that I've asked that 12-Oct-20 12:42 PM illustrates something 12-Oct-20 12:42 PM even the place in europe with a postdoc recently graduated from berkeley, that had good glasses uses, just had communal pairs 12-Oct-20 12:46 PM We have an obligation to get you what you need. But if no one ever asks and, more importantly, no one bothers to check, it doesn’t happen. 12-Oct-20 12:46 PM Contrary to the behavior of some PIs, students are not disposable. 12-Oct-20 12:52 PM getting the glasses isn't the issue, really 12-Oct-20 12:52 PM there's no barrier of "oh you don't need to spend $1500 on a better pair of glasses, we have these which are fine" 12-Oct-20 12:52 PM there just isn't the "hey, maybe check out the glasses we have and compare with other models, see if there's anything that would work better for you and we'll buy them because it's worth it" 12-Oct-20 12:52 PM Different kind of bad. 12-Oct-20 01:55 PM Well, I’m happy to kick a desk on behalf of improving your university’s safety culture if you like. 12-Oct-20 02:13 PM realistically if you could just find some way to heavily incentivize them to get students to take the laser safety training they allegedly offer 12-Oct-20 02:13 PM I mean 12-Oct-20 02:13 PM the university has a list of people who have made purchase orders for lasers 12-Oct-20 02:13 PM the university has a list of people who are doing research with those people, be it undergrads or grad students 12-Oct-20 02:13 PM and the university has a list of people who have taken their laser safety course 12-Oct-20 02:13 PM the "cost" of making people who are only doing theory in those groups do the laser course 12-Oct-20 02:13 PM or people who have done a laser safety course at another university having to do another 12-Oct-20 02:13 PM just seems well worth actually having all people who might touch laser stuff have some information forced on them 12-Oct-20 02:13 PM Heck, withold pay from grad students who haven't taken the course but are in a group that ticks the boxes. 12-Oct-20 02:13 PM As-is the only issue with ignoring it (besides safety itself) is liability 12-Oct-20 02:55 PM funny enough it wasn't laser injury that got me to take laser safety seriously, it was a blood vessel popping in my eye and introducing 15 floaters that gave me a preview of what a laser eye injury might look like, that did it instead. 12-Oct-20 02:55 PM i blame the university "pile homework on you and drink coffee to deal with it you pleb" culture, for that one. 12-Oct-20 02:55 PM at that point I decided it wasn't worth the health risk to keep up with the toxic uni culture, quit shortly after to work on electronics full time (and bought some nice laser glasses for my tomfoolery). 12-Oct-20 02:57 PM Those of us spending the most time with the equipment don’t have any other duties 12-Oct-20 03:06 PM when you are a kid you feel invincible and then when you get older stuff starts breaking down on you and changes the attitude. 12-Oct-20 03:06 PM interestingly the pyrotechnics culture tends to have a really good safety attitude compared to a lot of other fields, i think it is the examples you find of people missing fingers that makes the youngsters take it seriously. 12-Oct-20 03:28 PM i blame the university "pile homework on you and drink coffee to deal with it you pleb" culture, for that one. @adammunich I totally understand that one. I became seriously sick about a year after starting to study electrical engineering. But I stayed for what I wanted there, which is electrical engieering itself 12-Oct-20 03:29 PM it's really bad, but I hear MIT has it worse, and students suicide regularly 12-Oct-20 03:30 PM if you crunch the numbers, mental health probably does have a better return on investment for what to improve. But yech. 12-Oct-20 03:30 PM MIT sounds like horrendous student loans to me. Fortunately none of that is the case for me 12-Oct-20 03:31 PM if you crunch the numbers, mental health probably does have a better return on investment for what to improve. But yech. @idmb it's hard to do anything when you are messed up emotionally, let alone make significant contributions to academic fields 12-Oct-20 03:37 PM True! Mental and emotionall awareness both deserve more attention and shouldn't be tabooed by society in my opinion 12-Oct-20 03:37 PM Yep 12-Oct-20 04:41 PM Many years ago, after a spate of suicides, the University of Washington's Physics Dept. was assigned to the Psychology Dept. on the grounds of "Can you please figure out what's going wrong and fix it?" Psych declined on the grounds they'd already been tasked to figure out what was wrong with the med students. 12-Oct-20 04:47 PM SFU just blames it on the mountain 14-Oct-20 01:08 AM So the CNC machine I order came with a 1W laser module and a pair of laser goggles 14-Oct-20 01:08 AM Looks cool and all but 14-Oct-20 01:08 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20201014_160221-795DF.jpg 14-Oct-20 01:08 AM Yeah, need a proper pair of goggles 14-Oct-20 01:10 AM Methinks they're rated for other wavelengths than green 14-Oct-20 01:10 AM The laser module it came with is rated 450 nm iirc 14-Oct-20 01:10 AM So it's going towards blue-ish? 14-Oct-20 01:10 AM I wouldn't bet on this protecting my eyes though 14-Oct-20 01:10 AM I ran it through a diffraction grating 14-Oct-20 01:10 AM Seems like it blocks out red 14-Oct-20 01:23 AM yeah maybe it's for blocking the pumper and Nd:YAG wavelengths (808 and 1064) of green laser pointers 14-Oct-20 01:28 AM This is the laser 14-Oct-20 01:28 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG-20201014-WA0001-4E842.jpeg 14-Oct-20 01:28 AM But anyway 14-Oct-20 01:28 AM Anyone who uses that pair of goggles with this 14-Oct-20 01:28 AM And has the beam get into their eye somehow 14-Oct-20 01:28 AM Owwww. 14-Oct-20 01:28 AM This is quite certainly not going to help you at 450 nm 14-Oct-20 01:32 AM yeah 14-Oct-20 01:32 AM my guess is they were intended for green laser pointers 14-Oct-20 01:32 AM and they cost negative so they dispose them to the package 14-Oct-20 01:32 AM not for protecting against green 14-Oct-20 01:32 AM normal laserpointer customer want's to see what he's paying for 14-Oct-20 01:41 AM 1W laser though 14-Oct-20 01:41 AM That's certainly NOT laser pointer powers 14-Oct-20 01:46 AM not? 14-Oct-20 01:46 AM to low? 14-Oct-20 01:46 AM there was a hype about high powered laser torches sone years ago 14-Oct-20 01:46 AM some 14-Oct-20 01:46 AM like it's not enough power if you can't light a tree standing 100m away on fire 14-Oct-20 01:46 AM "permanent laser pointer" 14-Oct-20 01:50 AM I mean that much more than laser pointer powers thank you 14-Oct-20 01:53 AM le me remembers virtually everyone having one and stupidly setting things on fire with it - or burning holes in it 14-Oct-20 01:53 AM cutting duct tape ... 14-Oct-20 01:53 AM but then some more braindead idiots started pointing them at planes, helicopters and cars 14-Oct-20 01:53 AM since then they're kinda banned here - I dunno 14-Oct-20 01:53 AM haven't seen kids playing with such lasers outside for a while now 14-Oct-20 02:06 AM Yeah the danger with a visible high power laser is less than the danger of a high power invisible... Though I don't know how much less 14-Oct-20 02:06 AM In this case since they're coincident it may be moot 14-Oct-20 08:08 AM Never trust the goggles those laser pointer companies include for "free" 14-Oct-20 08:16 AM [squints at @SleepyOwl Joyce's pic] That's getting closer to a compliant label. My trust in the manufacturer is ever so slightly higher. And indeed never trust free gogs. 14-Oct-20 09:39 AM I still like how the green laser pointer I bought that measures in at 80 mW after installing an IR filter says "less than 5 mW" on the label 14-Oct-20 09:53 AM Same, same 14-Oct-20 09:53 AM I bought mine when I was 13 14-Oct-20 09:53 AM Shouldn’t be a thing 14-Oct-20 10:04 AM I have a feeling the cheap laser pointers will be a lot harder to get in the USA after the recent events than they used to be... Probably for the best I suppose...? 14-Oct-20 10:05 AM Maybe the barrier to figure out where to order them 14-Oct-20 10:21 AM I really, really wish they would be. I am sad to report as someone who has tried to fix this problem that unless Amazon, Aliexpress, eBay, Facebook, Wish, etc. decide that they don't like money, it won't be. The FDA-CDRH and USPS have more or less done a tableflip and headed to the bar. They have been sufficiently hamstrung that they're powerless to stop the tsunami of BS gray/blackmarket items those companies are playing 3rd party broker for. Having been snippy at some Amazon engineers once over drinks, they at least had the shame to admit they could fix this overnight if there was any interest to do so. Things ain't great. 14-Oct-20 10:25 AM isn't it post services that you need to deal with? 14-Oct-20 10:25 AM like maybe amazon / aliexpress / whoever are making it accessible 14-Oct-20 10:25 AM but with post the way it is, you're never going to be able to block out sites like dealextreme ? 14-Oct-20 10:25 AM Maybe some laws could change credit card usage for those purchases 14-Oct-20 10:25 AM but like, kids can still figure out bitcoin etc. 14-Oct-20 10:27 AM The falsified customs forms don't help either. As a test to see exactly how BS a laser I could get, which I promptly shoved in those Amazon engineer's faces, the package that arrived for me was tagged "Remote control and camera parts". Not "Class IV hand held laser". 14-Oct-20 10:27 AM I think "pen" is a normal one 14-Oct-20 10:27 AM And though I'm sure 99% comes from china 14-Oct-20 10:27 AM it's not like just better scanning items through china would stop them 14-Oct-20 10:27 AM You can pay $5 USD and it's still worth it for the company to make the laser, and ship it. If to ship it via some other country cost $25/40, people would still pay it. 14-Oct-20 10:30 AM Ebay would still be a problem, but not being able to get a thing that can blind you for $5 on amazon is definitely a start 14-Oct-20 10:30 AM And like eventually, they could just embed the laser diode on some other PCB for some other device and sell them some weird roundabout way that way. Such an awful situation 14-Oct-20 10:30 AM That's the "tsunami of BS" part. The postal inspectorate could step up their Customs game, except that much of our Customs roles are now handled by DHS under Immigration & Customs Enforcement. As you may have noticed in the last several years, they are WAY more excited about the I part of ICE, rather than C. 14-Oct-20 10:31 AM Ebay very clearly doesn’t care about almost anything given it was nearly possible to sell a fairly large chunk of radioactive material there recently 14-Oct-20 10:31 AM @funranium but if they stepped it up, it would arms race wouldn't it? I guess as an end goal you could price out kids, maybe.. 14-Oct-20 10:32 AM A little extra hassle is a great way to slow a lot of people down 14-Oct-20 10:32 AM ^ 14-Oct-20 10:32 AM Like, yes, you could put a high power diode on a junk circuit board, but most people won't actually make their own pointer 14-Oct-20 10:32 AM And you could also uniformly ban anything that's plug in or not AA battery 14-Oct-20 10:32 AM Or similar battery 14-Oct-20 10:32 AM Because a legal laser pointer isn't going to have a 16500 in it 14-Oct-20 10:40 AM In short, there's some perverse incentives to not check for things. There aren't enough people to check, a vast number of different things to check for in the ocean of things being shipped, and the focus has been moved. And the companies enabling it are very, very happy to take their small percentage of whatever and get to claim that any malfeasance is on the part of the seller, not them. Which is a much bigger problem than just lasers which have sort of never gotten properly regulated. 14-Oct-20 01:36 PM lazor 14-Oct-20 01:59 PM Those glasses they include with cheap but very powerful lasers are little more than colored polycarbonate honestly... Near useless no matter the wavelength 14-Oct-20 04:32 PM @funranium has discovered amazon's business model: there is no counterfeiting in ba sing se, if no one inspects the mail in ba sing se. 14-Oct-20 04:32 PM Because a legal laser pointer isn't going to have a 16500 in it @Mezmorizor challenge accepted 14-Oct-20 04:52 PM Okay, let me rephrase. There's no good reason to put that much battery on a 5 mW pointer. I don't doubt that you can make it work 15-Oct-20 01:19 AM 5MW 15-Oct-20 01:23 AM Here's a thought provoking question 15-Oct-20 01:23 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/Screenshot_2020-10-15-16-18-36-551_com.wha-1BF69.jpg 15-Oct-20 01:23 AM I am thinking if buying one of those Nd:YAG lasers they use for ratio removal 15-Oct-20 01:23 AM And then pumping it with a 808 nm diode 15-Oct-20 01:23 AM These have a passive Q-switch in them 15-Oct-20 01:23 AM So I wonder if this can be made to do metals 15-Oct-20 02:16 AM @SleepyOwl Joyce $3000 on ali gets you a fiber laser machine that can engrave 1mm into copper nowadays 15-Oct-20 02:18 AM I see 15-Oct-20 04:25 AM @Mason_Yu can you post a dump of all the strings you found in that atmel 15-Oct-20 04:24 PM @adammunich There is no meaningful ASCII strings that I can find in both binaries. You can take a look at them yourself using this website here, but it looks like the compiler they used have removed all comments http://binvis.io/#/ 15-Oct-20 04:24 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/flash-E4716.bin 15-Oct-20 04:24 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/eeprom-649DB.bin 15-Oct-20 10:19 PM @adammunich I think @Mason_Yu can get those sort of lasers under $1k if i remember older conversations correctly 15-Oct-20 10:19 PM I did get a 50W DPSS Nd:YAG laser with a q-switch for $500, there are cheaper modules too, but without the q-switch 15-Oct-20 10:19 PM Cooling it has been a bit of a headache, it requires high pressure water at a decent flow rate, and the inlet temp should be chilled or at least room temp 15-Oct-20 10:19 PM Fiber lasers are more expensive, and you can't really DIY it, but if you just want to engrave, then the DPSS modules with a q-switch is just fine 15-Oct-20 10:19 PM This reminds me that I'm still missing the driver for the q-switch 15-Oct-20 10:22 PM Done 15-Oct-20 10:30 PM @Mason_Yu what rep rate does that YAG do?.. 15-Oct-20 10:32 PM It depends on the q-switch, it's rated up to 50 kHz I believe with the driver from factory, but I think it can be pushed further 15-Oct-20 10:35 PM Is it only 50W at 50Khz, then? 15-Oct-20 10:35 PM this is the kind of scaling I expect 15-Oct-20 10:35 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-DFE0D.png 15-Oct-20 10:36 PM No, 50W average, at 50 kHz the average power would be a bit lower, since the q-switch would absorb a fair amount 15-Oct-20 10:36 PM average power is an asymmetric curve 15-Oct-20 10:36 PM 50 kHz is like the upper limit of that curve 15-Oct-20 10:37 PM but still probably >20W at 10KHz 15-Oct-20 10:37 PM Which is a lot. 15-Oct-20 10:37 PM Yeah absolutely, at that power the cooling requirement for the q-switch is more significant than the DPSS module itself 15-Oct-20 10:37 PM The q-switch requires a lot more flow, while the module require low inlet temp 15-Oct-20 10:39 PM each of our ascends has its own 6000 series chiller, yeah. 15-Oct-20 10:39 PM They don't just need a lot of water though 15-Oct-20 10:39 PM they need a steady temperature 15-Oct-20 10:39 PM at least for most purposes 15-Oct-20 10:44 PM And at a high pressure, there are essentially microchannels machined into the coolers for the diode bars in each of those modules 15-Oct-20 10:47 PM with the chiller directly beside the laser they set it at 50 psi 15-Oct-20 10:47 PM with 10m hoses, 70 psi 16-Oct-20 05:52 PM i got some 808nm 40 watt fiber laser about $80 planning to use marco's laser driver on it :> https://github.com/marcoreps/laser_driver https://www.coherent.com/assets/pdf/COHR_FAP800Series_DS_0917_1.pdf 16-Oct-20 06:19 PM Nice I have one of those too 16-Oct-20 06:19 PM I have a 100 watt YAG amplifier with built in pump diodes I haven't used ever, maybe I should sell it 16-Oct-20 06:23 PM ah dad wants to use it to cut things like thin frabric other friends online were unsure about it being the right wavelength or strength for that 16-Oct-20 06:23 PM what kinda lens would we use anyway? Zinc Selenide? 16-Oct-20 06:31 PM You can just use N-BK7 16-Oct-20 06:31 PM Though I'd be surprised if that's enough to cut it 16-Oct-20 06:35 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-629CA.png 16-Oct-20 06:35 PM so... 1.00 would be perfect transmittance? nothing absorbed at that frequency? 16-Oct-20 06:35 PM whats the 10mm / 25mm? how thick the sample of glass was they tested? 16-Oct-20 06:35 PM in other words 0.999 is 99.9%? 16-Oct-20 07:41 PM Yes, yes and yes 16-Oct-20 07:42 PM thanks 16-Oct-20 07:42 PM For that kind of laser you want anti reflective coating 16-Oct-20 07:42 PM Or you may send a whole watt backwards 16-Oct-20 07:42 PM oh shoot 16-Oct-20 07:42 PM i figured 16-Oct-20 07:50 PM https://www.ebay.com/itm/Thorlabs-LA1951/114330870725 16-Oct-20 07:50 PM so something like that then right? 16-Oct-20 08:01 PM Doesn't specify the coating frequency 16-Oct-20 08:01 PM Make sure it's for 1064 ish 16-Oct-20 08:01 PM Or you may reflect / more / light 16-Oct-20 08:06 PM ah 16-Oct-20 08:25 PM Thorlabs B coating is 650-1050 16-Oct-20 08:25 PM And a thing to keep in mind that's realistically very minor, but shorter focal length lenses focus to tighter spot sizes 17-Oct-20 09:59 PM https://www.youtube.com/watch?v=hikH4sCk0F4 17-Oct-20 09:59 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-D1F12.png 18-Oct-20 12:52 AM That's incredible 18-Oct-20 12:52 AM Time to read about this 18-Oct-20 11:41 AM Wow that is lit. Now I know what to do with some of my lazors 18-Oct-20 11:41 AM I bet it works as well on humans too 18-Oct-20 11:41 AM Just need a higher frame rate camera 18-Oct-20 11:53 AM As a reminder, for a good chunk of the world, use of lasers on animals and humans is one of those things that can get you in rather deep trouble with the institutional review boards if you do it without prior submission & approval of your proposal. The kind of trouble where you are expelled/fired and your lab may never get funding again because they let you get away with it. In particularly bad cases, you may face criminal charges. If you want to expose yourself at home, help yourself. Leave the pets alone, though. 18-Oct-20 12:09 PM You don't need much power for this, not any more than the veinveiwer. In fact, you probably want to use those super low power single mode diodes for a better result here. 18-Oct-20 12:23 PM For animal and human use, there’s no power cutoff. If you’re using it, you state it as part of your protocol for review. And this is not a NV gambling license kind of review where “The application is on the stack, I can proceed pending denial.” This is do not proceed without approval. But this is not a caution for you @adammunich. Have fun lasing yourself in the privacy of your home. 18-Oct-20 12:25 PM What I'm curious about is whether or not you can isolate the motion of blood from the other tissues, either by using different frequencies or just by looking at motion on separate time scales. It seems to me like it would be a really good way to observe blood flow problems. 18-Oct-20 12:27 PM Pretty sure the Ig Nobel in physics was unironically about that this year 18-Oct-20 12:27 PM Dunno if speckle imaging is what you want 18-Oct-20 12:27 PM But in general that's doable 18-Oct-20 12:27 PM https://www.nature.com/articles/s41598-020-65295-4 18-Oct-20 12:27 PM Granted the theory is more complicated for a not worm 18-Oct-20 01:27 PM @Haru That looked suspiciously like spam. If it wasn't, try #off-topic-thats-sometimes-on-topic for that. 18-Oct-20 01:27 PM ah gotcha 18-Oct-20 01:27 PM it was a tangeant ignoble prize 18-Oct-20 01:48 PM My favorite IG one is the diamagnetic floating frogs, IIRC that person also went on to win the other nobel prize too. 18-Oct-20 01:57 PM He did 18-Oct-20 08:27 PM I had to put my laser in storage I am cleaning up my house to get it ready to list and a laser on the kitchen table is probably a bit too much for potential small families who would probably be buying this place. The chem locker in the garage can simply just be locked. I know that I will now be coming up with tons of uses for the laser now that it’s sitting unused across town. In the building it’s in there is zero ventilation so I can’t use it there. 18-Oct-20 09:26 PM Most of my lasers need some kind of hacking to get working, they are safer this way. 18-Oct-20 09:26 PM I do want to make an eye safe laser lamp one of these days though, it would be very fun to have a properly monochromatic light fixture. 18-Oct-20 09:26 PM I need a frosted glass orb I can fill with some kind of diffuser fluid. 19-Oct-20 05:40 AM As a reminder, for a good chunk of the world, use of lasers on animals and humans is one of those things that can get you in rather deep trouble with the institutional review boards if you do it without prior submission & approval of your proposal. The kind of trouble where you are expelled/fired and your lab may never get funding again because they let you get away with it. In particularly bad cases, you may face criminal charges. > If you want to expose yourself at home, help yourself. Leave the pets alone, though. @funranium Doesn't that only apply in academia or corporate context? For family and friends it would all be contract law and/or child welfare 19-Oct-20 05:40 AM And I guess whatever laws surround pets, though vermin/pests are probably screwed 19-Oct-20 11:54 AM It applies pretty much anywhere that isn’t your home where you aren’t working alone. When you start experimenting on people and animals without oversight anywhere, you are starting down the path to Mengeleland (not affiliated with Disneyland) in the eyes of the law. No contract can absolve you of liability in this. And when your subjects show up at the doctor or vet’s office, phone calls will be made for child/domestic abuse/animal welfare. Nor is it okay to go blasting “pests”. Your local environmental quality and/or fish & wildlife folks have some opinions on what a pest is and who gets to control them and how. 19-Oct-20 12:27 PM Basically, in the eyes of the law and regulators if you want to do animal & human subject use, you join an institution first so you can get that ethics oversight and institutional support so you appear to be on the up and up. Not doing this leaves you in mad scientist and "quiet loner" territory when the headlines happen. As a general rule, whenever you're thinking doing a project, take a moment to ask yourself "Would I like to see this show up on the front page?" And no, home projects are not likely to get there for good reasons. 19-Oct-20 12:30 PM I wonder what kind of certs one needs for these https://www.pragdirect.co.uk/laser-bird-scaring-torch-new 19-Oct-20 12:30 PM Hah, it just might be "don't f'up and don't get caught" https://www.pestcontrolnews.com/laser-technology-bird-control/ 19-Oct-20 12:33 PM Pretty much. They’re safe in the “installed correctly, operating as instructed, and no one ever looks from the direction you’re not expecting” sense of safe. 19-Oct-20 12:33 PM Those are handheld, so dunno about "installed" 19-Oct-20 12:34 PM Rapidly scanning Class 4 to get it down to Class 2M is what most of the bird deterrence gear sold out of China is. Heaven help the workers doing overhead work in the train stations they’re installed in. 19-Oct-20 12:34 PM They’re not approved for use yet in the US. ConAgra wanted them for crop coverage. It was then pointed out to ConAgra that their farms covered an awful lot of flight path for open air use. 19-Oct-20 03:27 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-178A9.jpg 19-Oct-20 03:27 PM Wifi beam focus eh 19-Oct-20 05:29 PM hey y'know those red/green lasers that people buy to cover their house in red and green spots? a local marina/ferry stop was using 'em in their lawn to scare geese away theres a nearby hill with lots of car traffic i usually drive down that hill as a passenger looking out my window i got a blindingly bright green flash every damn time 19-Oct-20 05:29 PM one day i saw someone go down and into the marina and angrily rip every one of 'em out of the ground 19-Oct-20 05:29 PM lol 19-Oct-20 05:29 PM they kept using them the wrong way but eventually stopped and gave up on scaring the geese they tried everything 19-Oct-20 05:43 PM When those hit the market for the first xmas displays, there was a collective groan from the LSOs of the world. It takes very little effort to make those not safe, assuming they were in the first place. 19-Oct-20 05:43 PM So many laser dazzle events. 19-Oct-20 05:48 PM what are the stats for injuries from stuff like that? 19-Oct-20 05:52 PM idk but it pissed off airplanes a bunch of times from homeowners aiming it the wrong way 19-Oct-20 05:53 PM oof 19-Oct-20 05:55 PM oh reminds me on a slighty related tangent a couple years ago i saw a dummy shining one of those cheap AA powered green lasers (that are actually a lot brighter than the stated 1mW) at a lot of things he shouldn't have 19-Oct-20 05:55 PM like planes, random apartment buildings, cars... 19-Oct-20 05:55 PM everyone collectively called the cops on him simultaneously 19-Oct-20 05:55 PM i didn't stick around but i did see officers talking to him hehe 19-Oct-20 07:17 PM No laser injuries I know of but auto accidents? Yes. Dazzlers are bad. 20-Oct-20 10:28 AM isn't there also the problem that the green laser "stops" working in some of this xmas lasers when it gets to cold? 20-Oct-20 10:30 AM Probably. It's very nonideal conditions for a green laser pointer 20-Oct-20 11:08 AM @noclue a lot of cheap ones heat themselves up enough to work again 20-Oct-20 03:35 PM i disassembled one of those xmas lasers a bit ago and there's a large resistor socketed into the heatsink that i think is used for exactly that 20-Oct-20 03:39 PM that makes me like them a tiny bit. 23-Oct-20 11:23 AM I think I asked this a while ago and forgot the answer, but who makes good optical cement? 23-Oct-20 11:23 AM Oh wait, it was norland 23-Oct-20 11:23 AM Nevermind 26-Oct-20 05:36 PM @funranium Sorry for the ping, but is an acrylic box covered with aluminum foil a stupid way to safely cover a MIR periscope? 1.35 to 5 micrometers would be the wavelength range 26-Oct-20 05:36 PM Kind of just realized that acrylic alone doesn't actually absorb at all there 26-Oct-20 05:36 PM Power would be ~30 mJ per pulse with 4 nanosecond pulses 26-Oct-20 05:36 PM at 10 Hz 26-Oct-20 06:12 PM @Mezmorizor MWIR can go through HDPE but I haven't tried PMMA yet. I can assure you that aluminum is reflective there though. 26-Oct-20 06:12 PM In fact a lot of things are super reflective there in a way that is almost eerie, human skin is extremely shiny. 26-Oct-20 06:12 PM I know it's 95% reflective there, but I don't know if that's really sufficient 26-Oct-20 06:12 PM Or how much it absorbs 26-Oct-20 06:12 PM And the PMMA graphs I found imply it has 100% transmission at these wavelengths 26-Oct-20 06:12 PM In theory it never actually touches the enclosure 26-Oct-20 06:12 PM But I don't like living in theory land when talking about periscopes ya know 26-Oct-20 06:14 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/received_2606246226295205-72DB2.webp 26-Oct-20 06:14 PM 3-5um 26-Oct-20 06:14 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/received_429829994345990-49D93.webp 26-Oct-20 06:14 PM My glasses here are opaque, they are polycarbonate 26-Oct-20 07:29 PM @Mezmorizor No need to apologize, it's what I'm here for. Foil cover is a very common and cheap solution for enclosure. You should make it common practice to check for tears in the foil before runs, just to make sure no one's been clumsy. It's not a solid engineering control but it does the business. 26-Oct-20 09:59 PM @Mezmorizor you can get aluminum foil tape from the hardware store that is much more robust than kitchen foil. 26-Oct-20 09:59 PM And it's adhesive backed 26-Oct-20 11:02 PM the adhesives on some foil tapes are horrifying. like, basically eggshell unremovable, probably test first if it needs to ever come off 26-Oct-20 11:02 PM i'm sure there're good vendors for reliable foil tapes but i don't know 'em 26-Oct-20 11:11 PM I use foil tapes outside in the sun and they don't come off easily. They are pretty permanent. 27-Oct-20 04:42 AM I could use PMMA for short waveguides in the 400nm regime, right? What's the common recipe for PMMA annealing? 27-Oct-20 04:42 AM like 100 deg celsius (below glas trans temp) for 30 mins should be good? 27-Oct-20 04:48 AM PMMA is pretty common for scintillators in the 380-420 nm range, so 400 nm should work perfectly 27-Oct-20 04:48 AM why do you want to anneal it? 27-Oct-20 05:29 AM I think he means for like post EBL +development 27-Oct-20 05:30 AM oh nvm then 27-Oct-20 05:31 AM https://aip.scitation.org/doi/abs/10.1063/1.4948863?journalCode=apc looks like 10 minutes at any temperature really... will work lol 27-Oct-20 06:38 AM yep 27-Oct-20 06:38 AM nice 27-Oct-20 06:39 AM so you want to make 400 nm big waveguides, not waveguides for 400 nm 27-Oct-20 06:54 AM both 27-Oct-20 08:30 AM I'll keep the tape in mind I guess, but I'm pretty sure I want the easily replaceable foil? It's on an optics table in a lab. It's not at all exposed to the elements, and if there is a rip or something, I'm pretty sure I want to just add a new sheet 27-Oct-20 09:15 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-2F007.png 27-Oct-20 09:15 AM safety/10 27-Oct-20 11:10 AM first thing I should try is something like power dividers or so? 27-Oct-20 11:10 AM @sushi what's that frame from? 27-Oct-20 12:34 PM As we're coming into the holidays, foil roasting pans are now available in quantity in the supermarkets. They're sturdier than Al foil orgami and make great small optical bench covers and are easily clipped to make holes for flight tubes. Hit 'em with a some flat black paint if you want. Anything to keep dust off those optics, maintain thermal stability and, as bonus, beams out of eyes. 27-Oct-20 03:52 PM @sushi what's that frame from? @N00N everyone in the comments already roasted him for not wearing anything but uh here https://www.youtube.com/watch?v=y6YW1sU9heY 27-Oct-20 11:49 PM ah fun 28-Oct-20 07:53 AM Never really thought about it but macor + my laser = no bueno 28-Oct-20 07:53 AM Have to be extra careful sending beams in or it burns, even low power unfocused 28-Oct-20 11:29 AM MACOR machinable glass ceramic is a white, odorless, porcelain-like (in appearance) material composed of approximately 55% fluorophlogopite mica and 45% borosilicate glass. https://morgantechnicalceramics.com/en-gb/products/macor-machinable-glass-ceramic/macor-properties/ 28-Oct-20 11:29 AM @idmb ^ that macor? 28-Oct-20 11:36 AM yeah 28-Oct-20 11:48 AM that page makes it sound pretty durable why does a laser hurt it? 28-Oct-20 12:28 PM Because chirped pulse ti sapphires are like terawatt peak powers 28-Oct-20 01:10 PM that was the centrifuge 28-Oct-20 01:10 PM 4W at 1Khz with 500ps pulse duration 28-Oct-20 01:10 PM the other pulse is toned down to a measly 150uJ in 120fs 28-Oct-20 06:53 PM MACOR is extremely expensive. With laser cutting services for alumina ceramic now available I have changed to that by stacking up laser cut layers rather than machining. 28-Oct-20 07:17 PM nowhere near as expensive as the machinist cutting it 28-Oct-20 09:06 PM @hedgeberg I know this is like 2 months too late but your weird optical thread reminded me of something. 28-Oct-20 09:06 PM Screw lathes. (Pun intended.) 28-Oct-20 09:06 PM When your only tool is a hammer, all your problems start to look like nails. 28-Oct-20 09:06 PM A friend had a CNC mill and wanted to make a threaded hole for an objective of a microscope. 28-Oct-20 09:06 PM And custom taps for that were crazy expensive. 28-Oct-20 09:06 PM So he bought a thread mill 28-Oct-20 09:06 PM This is the weirdest tool I’ve seen in my life. 28-Oct-20 09:06 PM It’s sized for thread pitch but not diameter. It works for any diameter (as long as you can bore a hole big enough to fit the thread mill into.) 28-Oct-20 09:06 PM You run it in a helix around a hole you’ve bored. And it cuts threads. 28-Oct-20 09:06 PM Unlike rigid tapping, the RPM of the cutter has no relation to the movement or speed of the tool. The spindle rotation doesn’t have to be synchronized in any way with the tool movement. 28-Oct-20 09:06 PM Now the x, y, and z movement must be synchronized. It must be a helix of the property pitch. 28-Oct-20 09:06 PM You can continue cutting paths of increasing diameter until the thread fits. 28-Oct-20 09:06 PM Found pics 28-Oct-20 09:06 PM https://twitter.com/ryanpierce_chi/status/872951609365540864?s=21 28-Oct-20 09:06 PM https://twitter.com/ryanpierce_chi/status/872951953600413696?s=21 28-Oct-20 09:06 PM https://twitter.com/ryanpierce_chi/status/873151605423706112?s=21 28-Oct-20 09:06 PM I believe you can also use the same thread mill tool for an outside thread. 28-Oct-20 09:06 PM Although that probably is a better job for a lathe. 28-Oct-20 09:06 PM I know Fusion 360 CAM does thread milling, but they are a dirty word to me right now after they screwed over the maker community by nerfing their hobbyist license. 28-Oct-20 09:30 PM Oh man, screw mills are super weird! 28-Oct-20 09:30 PM Screw lathes, at least, make sense in theory 28-Oct-20 09:30 PM Because, y'know, lathes are self-centering, and so long as you can get the right gear ratio set between the chuck and the tool stage feed screw, you can make basically any screw 28-Oct-20 09:30 PM But screw mills are bizarre. 28-Oct-20 09:30 PM @rdpierce looks like a great toy, tho. The good news is that my 3d printed adapter works perfectly. Printed it w/ FDM via a friends' printer, then got shapeways to print it in SLS resin. The SLS resin one works perfectly 28-Oct-20 09:30 PM The FDM one also works real well, just needs to be worked in and out of the target threads a bit to scrape off extra material. All in all, I'm pretty satisfied 28-Oct-20 09:30 PM What I'm way less satisfied with is that the frickin Z mount on my microscope snapped. Some kind of bearing just gave out and I haven't had time to go in and fix it yet 30-Oct-20 08:57 PM actually gets around to getting a Nd:YAG laser 30-Oct-20 08:57 PM Now I need to figure out how to do calibration of my calorimeter 30-Oct-20 08:57 PM unfortunately the calorimeter comes with no calibration data 30-Oct-20 08:57 PM looks like this: 30-Oct-20 08:57 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/2Q-CF326.png 30-Oct-20 08:57 PM this one is flash lamp pumped, so I need to also figure out the capacitor bank sizing for the flash lamp 30-Oct-20 09:18 PM @SleepyOwl Joyce ooh, what model? 30-Oct-20 09:18 PM / specs 30-Oct-20 09:18 PM Astral Scientech AC50HD 30-Oct-20 09:18 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-BDC37.png 30-Oct-20 09:19 PM I meant the YAG 30-Oct-20 09:20 PM unknown 30-Oct-20 09:20 PM it's a chinese Nd:YAG hand piece 30-Oct-20 09:20 PM used for a certain purpose 30-Oct-20 09:21 PM removing tattoos from white tourists who didn't know what letters symbols they got ? 30-Oct-20 09:21 PM yeah 30-Oct-20 09:22 PM ah. so maximizing burning power rather than peak power 30-Oct-20 09:22 PM I am using it for another purpose 30-Oct-20 09:22 PM a project more for my sanity than anything lol 30-Oct-20 09:22 PM which is why I need to figure out the calorimeter bit 30-Oct-20 09:22 PM for the record I am not buying the whole set, just the laser handpiece 30-Oct-20 09:22 PM building my own electronics for it 30-Oct-20 09:24 PM the electronics for our yag are 5x the size of the yag 30-Oct-20 09:24 PM I see 30-Oct-20 09:26 PM like a cubic metre of electronics box 30-Oct-20 09:27 PM I mean I'd think one of the largest things would be the capacitor bank? 30-Oct-20 09:28 PM I can't say, I just tell the person using it what to do with the beam to make their laser work 30-Oct-20 09:28 PM not my monkeysaurus 30-Oct-20 09:29 PM I see 30-Oct-20 10:06 PM The capacitors in our YAG our massive, yeah 30-Oct-20 10:06 PM So massive that googling "big capacitor" isn't finding any as big as they are 30-Oct-20 10:10 PM ? 30-Oct-20 10:10 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/278119_1463494-D8F01.png 30-Oct-20 10:10 PM or room sized capacitor banks? 30-Oct-20 10:10 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/vulcan_capacitor_bank02-333EB.png 30-Oct-20 10:16 PM Not as big as any of those thankfully 02-Nov-20 05:34 PM hmmmmmm 02-Nov-20 05:34 PM https://www.youtube.com/watch?v=PV3jfR-FUFc 02-Nov-20 05:34 PM lasers for anti-air and anti-drone 02-Nov-20 05:34 PM honestly I am not sure this is a great idea 02-Nov-20 05:42 PM Laser War is not a good idea. There's a reason we made an addendum to the Geneva Convention regarding it. It's bad enough with lasers that aren't intentional weapons getting re-purposed for war crimes, like they did in the Balkan Wars. 02-Nov-20 08:10 PM Let’s just set the whole world on Fire! That’s basically what would happen in we had like phasers from Star Trek. Omg the mayhem. Humanity within moments of them being reality would band together to destroy them. 02-Nov-20 08:10 PM https://tenor.com/view/set-phasers-to-blow-up-remmick-dexter-remmick-picard-and-riker-gif-13961729 03-Nov-20 03:42 PM here's a coherent beam profile 03-Nov-20 03:42 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/123412830_3961523783876847_552225002166584-53428.png 03-Nov-20 04:09 PM "I say Geneva, you hear Helsinki! You're fired Bob, you're f-in fired!" 04-Nov-20 03:39 AM so I tore open the laser 04-Nov-20 03:39 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/DKouTnEOBYyMrtZYeMUuWvuZ-F9C29.png 04-Nov-20 03:39 AM not the cavity though 04-Nov-20 03:39 AM removed the Cr:YAG crystal because there's no need for it in my application 04-Nov-20 03:39 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-BC511.png 04-Nov-20 03:39 AM seems like they sell spare parts, like the cavity, the mirrors, etc 04-Nov-20 03:39 AM going to keep the Q-switch and some other unused parts for future use 04-Nov-20 07:17 AM Neat 05-Nov-20 10:02 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20201105_190213-D5682.jpg 05-Nov-20 10:02 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/20201105_190229-C6651.jpg 05-Nov-20 10:02 AM got hold of a cute Ti:Sa Laser 05-Nov-20 10:14 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20201105_150714_038-95CAE.jpg 05-Nov-20 10:26 AM Nice 05-Nov-20 10:30 AM just need some 532nm pumpoptics for this one, i can use it as is but i need to install one of the Innova 90s and that sucks a little bit^^ 05-Nov-20 01:24 PM WOAH 05-Nov-20 01:24 PM @verschrottix what model, I've been wanting one of these for a long time 05-Nov-20 01:44 PM It's a TI-SPB from Schwartz Electro-Optics 05-Nov-20 11:26 PM I think I know how we can make everyone live longer --open source mri machine. How can we make it happen? 05-Nov-20 11:28 PM By staying on topic in the channels? 06-Nov-20 08:51 AM And the usual reminder about human use of anything. 10-Nov-20 08:34 PM All this “drone defence pew pew” stuff with lasers or RF is stupid IMO. If you’re really worried, best defence is a good aim and a shotgun. 10-Nov-20 08:37 PM A drone that can fly 500m in the air at 10m/s is like $500 10-Nov-20 08:37 PM So uh, good luck 10-Nov-20 08:39 PM sniper weaponry 10-Nov-20 08:39 PM train snipers to shoot drones 10-Nov-20 08:39 PM It’s easier to program drones to chase drones 10-Nov-20 08:39 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-6CD14.jpg 10-Nov-20 08:40 PM drones with guns 10-Nov-20 08:41 PM We are lucky the regulatory nightmare that is UAVs hasn’t been more of a problem here 10-Nov-20 08:41 PM Singapore now requires drone registration and all 10-Nov-20 08:41 PM after an incident at the airport 10-Nov-20 08:41 PM honestly... 10-Nov-20 08:41 PM you're just hoping that most people respect that 10-Nov-20 08:45 PM It’s required here, as effective as as the bans on those lasers funranium hates 10-Nov-20 08:45 PM Banning something you can easily build yourself is hard 10-Nov-20 08:46 PM yeah 10-Nov-20 08:46 PM even lasers can be assembled on your own with the know how 10-Nov-20 08:46 PM thing is that customs don't recognize optics or laser parts 10-Nov-20 08:46 PM even high power semiconductor diodes can be declared as photodiodes, etc 11-Nov-20 09:29 AM does anyone have experience with laser optics from aliexpress? 11-Nov-20 09:56 AM I know someone who got a fiber laser from aliex 11-Nov-20 09:56 AM for laser engraving 11-Nov-20 09:56 AM it seems to work 11-Nov-20 10:23 AM Repeated grounding of firefighting tankers in CA this summer has not made the drone community many friends this year. 11-Nov-20 11:46 AM Something something power something something responsibility... Problem is people don't see power they just see cheap tech toy and assume no power so that statement goes poof in their brains... shakes head 11-Nov-20 11:50 AM responsibility? What's that? Never heard of it 11-Nov-20 11:50 AM Unfortunately, drones are just difficult to regulate 11-Nov-20 11:50 AM Especially when they can be so easily built 11-Nov-20 11:50 AM And the parts 3D printed even 12-Nov-20 08:12 AM wonders what are the lower cost spectrometers out there than can do Visible-spectrum to NIR 12-Nov-20 08:12 AM I have been looking at some ThunderOptics stuff 12-Nov-20 08:12 AM seems like it's just some regular CCD camera and a diffraction grating 12-Nov-20 08:12 AM not sure it can do NIR for characterizing the spectrum of DPSS lasers and stuff like that 12-Nov-20 08:14 AM You get better results per dollar with a slit and photodiode 12-Nov-20 08:14 AM Look at the mcpherson spectrometer / monochromator boxes. They’re simple modular things, you can just use the same idea 12-Nov-20 08:19 AM so for those of you guys in the cold atom works, i'm trying to build a 2d mot that shoots atoms into a 3d mot 12-Nov-20 08:19 AM i want something that acts as an orifice 12-Nov-20 08:19 AM so that only the cooled axial atom beam goes to the 3d mot 12-Nov-20 08:19 AM does anyone know what to buy/make for this orifice? 12-Nov-20 08:24 AM do we have any people who do stuff that cold? 12-Nov-20 08:24 AM Mez and I are peasant many millikelvin 12-Nov-20 08:25 AM I'm not aware of anyone here who does real cold atom work, no 12-Nov-20 08:25 AM Or at least I've never seen anyone else talk about it 12-Nov-20 08:30 AM ah damn 12-Nov-20 08:30 AM okay maybe a simple question would be where can i buy something with a conflat flange with a mm size hole and is uhv compatible? 12-Nov-20 08:42 AM Do you have a decent drill press or lathe? Gonna be cheaper to DIY than custom order. Next best would probably be to bring a flange to a local machinist and pay them by the hour 12-Nov-20 08:43 AM Gotta agree. I've seen stuff like that made for differential pumping set ups, but they'd be a lot more than a blank and a drill press 12-Nov-20 08:44 AM I can share the designs I have for something similar 12-Nov-20 08:44 AM Overly complex 12-Nov-20 08:44 AM But allows the hole to move around. Not UHV-oriented in regards to virtual leaks and such though 12-Nov-20 08:46 AM Cheapest way is definitely to buy blank copper gasket and drill a hole on lathe by yourself - I used that for differential pumping in gauge calibration apparatus. 12-Nov-20 10:12 AM [pinches bridge of nose] No, postdoc, you cannot just "get in there to check things out" with your two photon microscope. You'll be overriding the interlocks that make that tool a pleasantly Class 1 laser system and also voiding all the warranties that your professor paid good money to have for their service contract. Yes you can do this but you shouldn't. Your spirit of inquiry is to be commended, but go read the damn manual if need that kind of fun. 12-Nov-20 06:37 PM Anybody have a good guide/primer/review for lock-in amplifiers? 12-Nov-20 06:46 PM The SRS manuals 12-Nov-20 06:46 PM They’re beautiful 12-Nov-20 06:46 PM https://www.thinksrs.com/downloads/pdfs/manuals/SR830m.pdf 12-Nov-20 06:46 PM Section 3 12-Nov-20 06:54 PM Thank you! 14-Nov-20 01:58 AM https://www.youtube.com/watch?v=le-0j1nojuw 14-Nov-20 04:05 AM Not a flange. He would want like a conflat on both sides of the plate so a standard blank flange won’t do it 14-Nov-20 04:05 AM A copper disc like a conflat gasket but solid. Then you drill the orifice in it. That would work. 14-Nov-20 04:05 AM @SleepyOwl Joyce Ocean Optics has some relatively cheap ones I think? 14-Nov-20 07:10 AM You can do that too I guess, but that's not at all what I was thinking. Probably better assuming virtual leaks don't prove to be an issue I guess because it would be easier to move the hole around with something orifice plate like, but I literally just meant putting a hole in the proper place on a blank. 14-Nov-20 07:10 AM And even then it doesn't really change much 14-Nov-20 07:10 AM Instead of a blank it's a double sided flange and a plate 14-Nov-20 06:21 PM I don’t understand how you would do it with a conflat blank because how would you connect the second vacuum chamber to the outside? Is there such a thing as a double sided blank? Or weld two blanks together then drill it? 14-Nov-20 06:26 PM Yeah, double sided blanks are standard. 14-Nov-20 06:26 PM https://www.n-c.com/Products/Flanges-Fittings-and-Adapters/Conflat-Components-and-Hardware/Double-Sided-Flanges/Blank.aspx 14-Nov-20 06:31 PM Double sidded blanks are super awesome. A friend built a rig that use them to diferential pump from atmosphere to 10-6 torr 14-Nov-20 06:33 PM Why...? 14-Nov-20 06:34 PM There was a beam passing the other way of the air 14-Nov-20 06:35 PM I guess I just don't get the desire for an air beam 14-Nov-20 06:35 PM This was at a radiation effects lab 14-Nov-20 06:35 PM Anyways, a less UHV-friendly but better way to set up a differential pumping thing 14-Nov-20 06:35 PM is drill a big hole in the middle of a double sided flange and then four tapped holes a couple cm away from it in each direction 14-Nov-20 06:35 PM make a piece like this with the aperture size you want in the middle 14-Nov-20 06:35 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-D6BCC.png 14-Nov-20 06:35 PM out of like 2mm thick stainless, much easier to drill 14-Nov-20 06:37 PM He built a couple of different conflat rig with different targets that could be bolted on the end of the thing 14-Nov-20 06:37 PM Some were thin film and some where heavy metal 14-Nov-20 06:37 PM and then a clamp like this, where the holes line up with the tapped holes in your flange and the notches in the other piece 14-Nov-20 06:37 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-7A9F6.png 14-Nov-20 06:37 PM Bad for virtual leaks but if you're not cycling to atmosphere frequently it won't matter. 14-Nov-20 06:38 PM Yeah the center of the flange was milled out and a plate and apurture holder were bolted on 14-Nov-20 06:38 PM The apurtures would ware out over time 14-Nov-20 06:38 PM Alternatively, I made this POS for making x-y adjustable skimmers: 14-Nov-20 06:38 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-963DE.png 14-Nov-20 06:38 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/SkimmerMount-B874C.STEP 14-Nov-20 06:38 PM (if you copy something like that, PLEASE use finer pitch screws for adjustment than 8-32. SMH) 14-Nov-20 06:49 PM Lol yes 14-Nov-20 06:49 PM They pull the same shit in some sem filament alignment stuff 14-Nov-20 06:49 PM It's such a pita 14-Nov-20 06:53 PM So long as I don't eff up, I won't ever have to align it again 14-Nov-20 06:53 PM If a future student has to... I hope they consider removing the parts and having the machine shop add some fine pitch threads in between... 14-Nov-20 06:57 PM How did you align it out side of vacuum? 14-Nov-20 06:57 PM Just centering it up on the conflat? 14-Nov-20 07:03 PM couple things 14-Nov-20 07:03 PM I have four differentially pumped chambers, with gate valves in between. the gate valves have viewports, so I can send a hene through to align any one chamber while the others are pumped 14-Nov-20 07:03 PM but also because of that, for all the chambers other than the final one (which has ~1E-8 pressures) it's only like an hour to pump down well enough to check the alignment 14-Nov-20 07:03 PM so a painful couple days of opening ~5 times and checking positions 14-Nov-20 07:06 PM Ok that kinda what I was expecting 14-Nov-20 07:06 PM Sucks but it works... 14-Nov-20 07:06 PM So long as I don't eff up, I won't ever have to align it again 14-Nov-20 07:06 PM I have to do the same thing on FEG SEMs for column alignment so I feel your pain... 14-Nov-20 07:06 PM it was like 2 weeks tops though 14-Nov-20 07:33 PM How much copper did you go through? 14-Nov-20 07:37 PM Since I'm not going <1E-8 on any but one chamber, I can use rubber gaskets 14-Nov-20 07:37 PM but also for this purpose, you can re-use the copper gaskets 2-3 times 14-Nov-20 07:37 PM and then when you're happy with the signal, waste another hour opening/closing just to put in a new gasket 14-Nov-20 08:31 PM Yeah I was wondering if you were just going to use Viton at a certain point. 14-Nov-20 08:31 PM When you reuse copper do you do it with a torque wrench and just increase it each time? 14-Nov-20 08:31 PM Thats what I have done when doing re-use 14-Nov-20 08:34 PM nah, just by feel 14-Nov-20 08:39 PM Lol I feel we all trend towards that 14-Nov-20 08:45 PM We don't have a torque wrench 15-Nov-20 10:54 PM https://www.youtube.com/watch?v=iwj78pR46zM 15-Nov-20 10:54 PM interesting method of making optical filters 16-Nov-20 05:28 AM @idmb wow thanks for the detailed advice. why is it better to drill a big hole with a small hole in the middle inserted by a separate part? 16-Nov-20 05:28 AM and how long does it take to pump out the virtual leaks from the tapped holes or contacting surfaces? 16-Nov-20 07:56 AM Drilling deep small diameter holes is tricky 16-Nov-20 07:56 AM And this way you have adjustment if your system isn’t quite aligned 16-Nov-20 07:56 AM The first pumpdown will probably take a few days, even if you try really hard to clean the threads. Later on, if you open for a couple hours it seems to just take like a day and a half to hit -8, a week or two for low -9 16-Nov-20 07:56 AM Use vented bolts of course. 16-Nov-20 06:32 PM I always find viton conflat gaskets feel harder to get in the right place, but copper ones “drop in” and you know they’re centered and in properly. And gaskets are always a huge PITA if the flange is vertical. 16-Nov-20 06:45 PM If it's going above 1E-8, just use scotch tape. Try to minimize the amount on the vacuum side, but it won't kill you. 16-Nov-20 06:45 PM I thought these would be nice: https://www.lesker.com/newweb/flanges/pdf/manuals/13-066-hd-mn-gasketclipinstructionsmanual.pdf but they... aren't 16-Nov-20 06:47 PM Kapton tape maybe 17-Nov-20 01:07 AM I usually use kapton tape even on copper gaskets - just keep it out of flange knife... 17-Nov-20 02:07 AM half of the reason I bought apiezon L is just to hold the viton gaskets in place 17-Nov-20 02:07 AM I saw the writing on the wall for this 12" vertical gasket I need to do 17-Nov-20 07:20 AM Kapton tape seems harder for the knife to cut if you mess up haha. 19-Nov-20 11:45 AM RIP telescope https://news.ycombinator.com/item?id=25151342 19-Nov-20 11:19 PM So my dentist called and asked if they could drop something off for me to look at and see if I could fix 19-Nov-20 11:19 PM Turned out its a 2w 808 laser 19-Nov-20 11:19 PM Used for healing canker sores or ulcers ect. 19-Nov-20 11:19 PM They even brought the safety glasses for it so that was nice 19-Nov-20 11:19 PM Seems like the IR laser itself is fine but the 5mw red guide laser doesn't work, so without visual feedback they didn't know it was actually still lasing. 19-Nov-20 11:27 PM well that's kind of a scary failure mode, at least from a UX perspective 19-Nov-20 11:37 PM Yeah that... should be interlocked with a photodiode? 19-Nov-20 11:37 PM even my spectra physics laser has photodiode interlocks here and there 19-Nov-20 11:45 PM Yeah I agree 19-Nov-20 11:45 PM I mean it does beep 19-Nov-20 11:45 PM When it's lasing so at least there's that 19-Nov-20 11:45 PM BUT you can turn the beeper off in the menue 19-Nov-20 11:45 PM And the foot switch is 2.4 ghz wireless 19-Nov-20 11:45 PM It's supposed to have LEDS on it but both of those are also gone? 19-Nov-20 11:45 PM So you can basically make it so there's no indication it's lasing except the tingly feeling of it burning your skin 19-Nov-20 11:48 PM on no 19-Nov-20 11:50 PM Surprising that sort of thing could be approved to be used if you can turn off the very meager safety features 19-Nov-20 11:56 PM Yeah I'm kinda surprised 19-Nov-20 11:56 PM I mean Ultimately it's made to burn skin bit 19-Nov-20 11:56 PM Still doesn't seem awesome 19-Nov-20 11:56 PM When I first powered it up I didn't think it was lasing at all 19-Nov-20 11:56 PM Didn't think the foot switch was wondering because the LEDs were not lighting up like the manual said 19-Nov-20 11:56 PM And I was of course treating it as if it was because invisible laser am I right? 19-Nov-20 11:56 PM There is a key on the foot switch at least 20-Nov-20 12:04 AM If the LEDs are there but dead and so is the guide laser maybe some static discharge killed part(s) of it but not others? Very odd design choice not to have a photodiode interlock as everyone was discussing 20-Nov-20 12:05 AM No there's pads for leds 20-Nov-20 12:05 AM And it looks like maybe the used to be there 20-Nov-20 12:05 AM And they do get voltage when they should be lighting up 20-Nov-20 12:05 AM It's all very strange 20-Nov-20 12:06 AM Is there any evidence of any recent soldering or anything? Almost sounds like someone else was "fixing" it before they brought it to you. 20-Nov-20 12:06 AM Also the foot switch with the LEDs is just a stand alone wireless unit 20-Nov-20 12:06 AM No not at all 20-Nov-20 12:06 AM I know these people they don't even know what a soldering iron is 20-Nov-20 12:07 AM I guess I just do not want to believe this is actually being sold to be used in a health care setting legally haha 20-Nov-20 12:07 AM Same 20-Nov-20 12:07 AM Like there's literally a led labeled LASING 20-Nov-20 12:07 AM It's a light guide from the the case to the smd pads 20-Nov-20 12:36 AM Isn’t a “laser emission on” LED a legal requirement? 20-Nov-20 12:36 AM There's a lot about this thing I have questions about 20-Nov-20 12:37 AM Maybe some cheap AliBaba thing they purchased just to make funranium upset 20-Nov-20 12:42 AM No actually 20-Nov-20 12:42 AM This is like the industry standard tool 20-Nov-20 12:42 AM its like 10k apparently 20-Nov-20 12:42 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/PXL_20201120_084428750-3BCC7.jpg 20-Nov-20 12:42 AM So this is the foot switch. Both of those LEDs do nothing. 20-Nov-20 12:42 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/PXL_20201120_085010208-0A7AA.jpg 20-Nov-20 12:42 AM And this is the laser itself minus the battery unit 20-Nov-20 12:42 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/PXL_20201120_085247325-37D3B.jpg 20-Nov-20 12:42 AM And this is the SMD LED pad 20-Nov-20 12:42 AM I was probing it so that's what the parks are probably from 20-Nov-20 12:42 AM I'm going to get the 2x objective out and see what it looks like under that 20-Nov-20 01:01 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/PXL_20201120_090056263-6CF4F.jpg 20-Nov-20 01:01 AM I really should be using diffusion on my ring light when I'm at this high of mag, but it looks like it was just ripped off the pads 20-Nov-20 01:01 AM This is definitely not a surface that has been reflowed. 20-Nov-20 01:01 AM Im just going to go ahead and tag @funranium so he has something fun to wake up to in the morning. 20-Nov-20 01:01 AM At this point I could replace the LEDs but without a guide laser I don't think its a good idea to use. 20-Nov-20 01:01 AM And seeing as this is a medical device I'm not opening up the laser head itself, so I'm going to recommend they replace it. 20-Nov-20 01:01 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/PXL_20201120_085947500-EE15B.jpg 20-Nov-20 08:30 AM Gee, thanks. [runs fingers through hair] Sooooo, there's quite a few issues here that you've all identified. The worst of them however is how a product like this even ends up used in a medical setting. The answer is the import controls on "spa equipment" are more or less non-existent. A very steady stream of "I'm sorry, you have what that does WHAT!?!?" flows into America mostly via Miami, America's Main Health BS Fountain. Plenty show up in NYC and LA as well but, wow, Miami is the big winner here. 20-Nov-20 10:20 AM Speaking of sketchy Spa equipment one of my friends got his hands on one of those high frequency muscle tone machines 20-Nov-20 10:20 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/received_323878458900056-95FCB.jpeg 20-Nov-20 10:20 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/received_369391830906320-35391.jpeg 20-Nov-20 10:20 AM It's toplogically identical to pair of coil guns 20-Nov-20 10:20 AM Large pulse capacitors with some thyristors 20-Nov-20 11:45 AM @adammunich My friend costruct those at BTL Medical Technologies 20-Nov-20 11:47 AM This one's the Shanzhai version 20-Nov-20 11:47 AM $3000 20-Nov-20 11:47 AM My other friend has been really interested in it as a means of muscle Rehabilitation 20-Nov-20 11:47 AM restoring muscle tone in people who haven't been able to walk a long time 20-Nov-20 11:47 AM Interestingly this China copy does work pretty well although the build quality is much lower than what I imagine the btl units are 20-Nov-20 03:44 PM Been playing around with a fiber laser. Cranking up the speed to see what the ablation spot size looks like. This is at lowest frequency (highest power-per-pulse) so likely worst case. Seems to hover around 30um which honestly is better than I expected. Apologies for potato quality, cell phone photo of ground-glass viewport 20-Nov-20 03:44 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-61052.png 21-Nov-20 04:40 PM https://seattle.craigslist.org/see/tls/d/trumpf-tla700-rf-co2-laser-700-watts/7227286197.html 21-Nov-20 04:40 PM This thing has been on craigslist for literally years now 21-Nov-20 04:40 PM Price was cut in half about a year ago 21-Nov-20 04:40 PM I just think its funny how persistent this person is 21-Nov-20 04:40 PM And also doesn't appreciate the power he is trying to hand someone. 21-Nov-20 04:40 PM https://seattle.craigslist.org/see/fuo/d/woodinville-trumpf-laser-resonator-table/7233269895.html 21-Nov-20 04:40 PM Lol just found this 21-Nov-20 04:40 PM @funranium looking for a new coffee table? 21-Nov-20 04:44 PM So many diode bars CO2 laser, I'm blind 21-Nov-20 04:45 PM Honestly I would totally use that as coffee table thats pretty cool. 21-Nov-20 04:48 PM Looks like it has a centrifugal water pump on top, feeding water to all channels 21-Nov-20 04:48 PM They should definitely replace the top cover with acrylic 21-Nov-20 04:48 PM What a beam path https://www.youtube.com/watch?v=7RHdkHVmp2Q&ab_channel=TRUMPFInc. 21-Nov-20 04:48 PM https://www.youtube.com/watch?v=AS__8VI4nW4&ab_channel=MidAtlanticMachineryInc 21-Nov-20 04:51 PM Price was cut in half, person could be cut in half too 21-Nov-20 04:53 PM SO fancy. 21-Nov-20 04:56 PM “Its turbine is spent” what does that mean? 21-Nov-20 04:58 PM Could be any number of things, mechanical failure of the blades, bearing problem...etc 21-Nov-20 04:58 PM Corrosion shouldn't be an issue in a water loop like this, but it could happen if there was poor maintenance, or there could be seals leaking and thus damage the motors 23-Nov-20 11:50 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/PXL_20201123_194944008-F5CC1.jpg 23-Nov-20 11:50 AM I have to clean an optic under this prism so all of this epoxy has to be slowly scrapped out... 23-Nov-20 11:50 AM It kinda sucks 23-Nov-20 11:50 AM Its one of those tedious jobs where if I slip up for a fraction of a second I destroy the prism... 23-Nov-20 11:50 AM Or slice my finger open 23-Nov-20 11:54 AM I like when you have a situation like that with an appropriate solvent available 23-Nov-20 11:54 AM Yeah and I unfortunately don't right now 23-Nov-20 11:54 AM Even then I cant soak this part because of other epoxy parts I dont want to attack 23-Nov-20 12:03 PM The epoxy in the hex heads will be fun 23-Nov-20 12:03 PM Those actually loosened up no problem 23-Nov-20 12:03 PM Surprisingly 23-Nov-20 12:04 PM Oh awesome! It looked like the same material as on the prism at the right 23-Nov-20 12:04 PM Very lucky that it was not! 23-Nov-20 12:05 PM yeah for sure 23-Nov-20 12:46 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/PXL_20201123_203355122-04D16.jpg 23-Nov-20 01:01 PM Finally got one out 23-Nov-20 01:25 PM Ugh the second one has twice as much epoxy 23-Nov-20 02:38 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/PXL_20201123_223539378-A83CE.jpg 23-Nov-20 02:38 PM Victory 23-Nov-20 02:38 PM That was awful 23-Nov-20 02:38 PM The second one had way more epoxy 23-Nov-20 04:17 PM You have done righteous battle. 23-Nov-20 04:18 PM I'm getting closer and closer to dropping a lot of money on first contact polymer 23-Nov-20 06:53 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/PXL_20201124_025251431-C2CF3.jpg 23-Nov-20 06:53 PM This is how dirty every single optic in this microscope is 23-Nov-20 06:53 PM Literally all of it 23-Nov-20 06:53 PM I really want to know where it was stored that this could happen to it 23-Nov-20 09:32 PM Downwind of the cement plant by the looks of it. Looks like my car's windshield if I don't drive it for a few days. 24-Nov-20 03:02 PM the camera I've been looking for inside the toolmaker's microscope was just listed with custom external cable attachments, used, in a project.. price is decent but I wonder if I could get him down some 24-Nov-20 03:12 PM Always worth trying 24-Nov-20 03:12 PM I msg'd asking about what specific connectrors they are, as he mentioned to connect external battery for dones, etc 24-Nov-20 03:12 PM but stated no problem sniping them off and crimping my own 24-Nov-20 03:12 PM he also has 3 of them, so no worries on missing out like I have before.. I mean, they are available, I just dont want to spend $500 on one, especially since the concept hasn't been proven just yet 24-Nov-20 03:50 PM yeah, molex connectors, says they just plug into the camera, so no modifcations in that regard 24-Nov-20 03:50 PM I asked about how he interfaced (WiFi or USB).. will give it a few days I think before I go for one, but no reason not to 24-Nov-20 03:50 PM beyond price 25-Nov-20 10:00 PM [rubs temples] Goddammit, spyro [pours another glass of holiday cheer] 25-Nov-20 10:01 PM :D 25-Nov-20 10:01 PM It was relatively tame tbh 25-Nov-20 10:01 PM Compared to the tens of watts things 25-Nov-20 10:01 PM ofc the server had it's fresh flood of noobs who now talk about DVD burners 25-Nov-20 10:03 PM I actually found it less tame 25-Nov-20 10:03 PM Handheld stuff is my biggest ugh 25-Nov-20 10:03 PM Peak pandemic I was bored enough to engage with the server a bit and am in the screenshots asking about why you’d want the tiny driver... 25-Nov-20 10:04 PM Who wanted to leave 2020 with 20/20 anyhow? 25-Nov-20 10:05 PM Oh something fun? 25-Nov-20 10:05 PM "badump-pish" 25-Nov-20 10:05 PM I got tested when I was 20 and was 20/6 so rip 25-Nov-20 10:08 PM Upgrading keychain laser pointer from 5mW to 3W. So from Class 3A to 4. 25-Nov-20 10:08 PM AKA from amusing to that's a war crime waiting to happen in your pants 25-Nov-20 10:11 PM Is there no extra rating for battery powered? 25-Nov-20 10:11 PM Speaking of laser power 25-Nov-20 10:11 PM My Metrologic 45-545 laser power meter only goes to 20mW 25-Nov-20 10:11 PM I have some diodes and other stuff which I suspect is more powerful, what's the established way to attenuate it to protect the power meter? 25-Nov-20 10:11 PM Or is the solution just "get a meter that goes higher" 25-Nov-20 10:13 PM No. Only output matters. 25-Nov-20 10:13 PM If you don't have output power control to just dial it down, neutral density filters. Or alternatively a 1% pick off to direct to the power meter. You may still need filtration for that. 25-Nov-20 10:14 PM Ok 25-Nov-20 10:15 PM Filters are way cheaper than new power meters. 25-Nov-20 10:15 PM I'm unsure how low some diodes go before they go from lasing to a led 25-Nov-20 10:16 PM Well, these are the kind of things your manufacturer data sheet should tell you. 25-Nov-20 10:16 PM Oh wait, I made a funny again. 25-Nov-20 10:16 PM Heh, if I had a datasheet I would not be this suspicious of them. 25-Nov-20 10:18 PM Seems like this should be changed/improved? Batteries are like handguns, power is like caliber / rate?... 25-Nov-20 10:18 PM It just seems so much worse to have a class 4 that isn’t tethered to something 25-Nov-20 10:21 PM Oh, I agree. There's some extra words in the standards and pretty much every country's regs that has them regarding handheld anything that's 3B & 4. Very frowned on. 25-Nov-20 10:21 PM "1% pick off" sounds like an optical directional coupler 25-Nov-20 10:21 PM With 20dB coupling 25-Nov-20 10:22 PM Health Canada, because of Wicked Lasers, made some very choice statements. 25-Nov-20 10:22 PM Yeah handheld anything over 1mW is pretty haram here 25-Nov-20 10:23 PM I have an issue where I have no idea where the “clearly I shouldn’t have bought these” lasers I got in high school are 25-Nov-20 10:23 PM I’ve moved thrice since then 25-Nov-20 10:23 PM I always get be very clear with my researchers that I hate these particular lasers when I find them in their labs but, however, this was the one place is okay for them to be. Because to possess them you need to have a laser safety program and LSO. Luckily, at work, they've got one. 25-Nov-20 10:23 PM Lost and likely broken questionably legal lasers are the best kind. 25-Nov-20 10:28 PM Only the kaleidoscope one is broken afaik 25-Nov-20 10:28 PM Though maybe the rest are corroded from batteries over the years 25-Nov-20 10:30 PM This reminds me, I promised to build Laser Murder Kits for the other LSOs in the UC system. I should do that for before the end of the year. Make a fine holiday present. 25-Nov-20 10:30 PM Ooh, what do those involve? 25-Nov-20 10:30 PM Mallet, small pry bar, and tin snips are the three fundamental tools. 25-Nov-20 10:30 PM The time I hit an argon system HARD with a mallet made UCSF's LSO wince like I'd just hit a baby with it. I then gave a second more gentle tap and the coupler fell into my palm. I handed it to the LSO and said "First hit breaks the Loctitie. Keep that. That's a trophy from your first laser murder." 25-Nov-20 10:33 PM When does this happen? 25-Nov-20 10:35 PM When a laser is being sent to salvage for scrap. Effort must be made to make it non-operable lest dumpster divers, AKA students and enterprising members of the local community, decided to dig it out and plug it in again. 25-Nov-20 10:35 PM While there's no hard and fast rules, the people that just cut the power cord and call it good clearly don't know what Day 1 for an apprentice electrician is. My personal standard is "It will cost more to fix this when I'm done than buying a new one." 25-Nov-20 10:37 PM I guess our lasers are special in that all the cost is crystal, pockels cells, gratings, and diode bars... which we use until they die 25-Nov-20 10:38 PM A class 3B or 4 laser being sold needs to be going to someone else with a laser safety program and LSO. If it's not, they have to be rendered inoperable. 25-Nov-20 10:38 PM But also we still have the forty year old ones, posing an earthquake hazard up high. 25-Nov-20 10:39 PM So, for systems like your laser I do something much more wholesome to. 25-Nov-20 10:39 PM (One in particular, I don’t understand why it got put there... when the original 1978 shipping crate was in the closet?) 25-Nov-20 10:39 PM We really shouldn’t have universities in such nice cities 25-Nov-20 10:39 PM We should all be in Saskatchewan with an aircraft hanger for each lab 25-Nov-20 10:39 PM No need to dispose of nefarious junk 25-Nov-20 10:41 PM I get positive affirmation, usually in writing from the PI, that they want nothing on this setup anymore. At which point I quietly let the students I know that deserve nice things in their life that there is a carcass of a system ready for pillaging of componentry. The optical bench is usually clean within an hour. 25-Nov-20 10:42 PM Students with affiliations to groups, or you do actually let them take stuff home? 25-Nov-20 10:43 PM Oh no. All that gets to stay on site. Lab shuffle. 25-Nov-20 11:05 PM One time they ordered four too many subway catering trays 25-Nov-20 11:05 PM That email drew quite a crowd of grad students after the seminar 25-Nov-20 11:11 PM Now imagine if you did that with pizza and a keg suddenly appeared in the quad. THAT'S what optics salvaging operations are like. 25-Nov-20 11:14 PM The other physicists don’t even know where our building is 25-Nov-20 11:46 PM That description reminds me of folks when some good junk is brought to the radio club I'm a member of 25-Nov-20 11:46 PM Or that time we parted out that 300k€ Anritsu cellphone protocol tester "Hey this thing cannot go out of that door in pieces larger than a kilo" 25-Nov-20 11:46 PM --> 1.5hours later we have a neat pile of aluminium plates and are looking up datasheets for the neat RF parts on the boards :D 26-Nov-20 12:36 AM Now I understand why my PI has like 7 large old Class 4 Nd:YAGs just sitting there that we never use 26-Nov-20 12:36 AM They don’t deserve the hammer 26-Nov-20 12:36 AM Speaking of which, I should remember to get my baseline retinal photos and ophthalmology exam done, supposed to be done before I started Class 4 work but I’ve been going a while without it 26-Nov-20 12:36 AM Can I use a UV light to distinguish a wafer of quartz from one of glass? Short wave UV transmission seems like the easiest way to do it 26-Nov-20 01:04 AM It seems like “stupid laser pointers” were so 2015 to be honest, they’re less common now, and more regulated. Dodgy Class 4 laser “Maker” products are the hazardous laser product of questionable legality under the Christmas tree for 2020. 26-Nov-20 01:05 AM Can I get that little cube thing for 500$ please? 26-Nov-20 01:06 AM Little cube thing? 26-Nov-20 01:37 AM One of those open air laser engravers where it's a cube with galvos instead of an enclosed cube 26-Nov-20 01:59 AM Ah yes I know the one. Class 4 laser in free space, not constrained in a fixed plane, bouncing around on galvos, no enclosure or shielding, no key switch or interlock etc 26-Nov-20 02:11 AM That one 26-Nov-20 09:37 AM Oi... universities are so wasteful 26-Nov-20 09:54 AM so strongly net positive that it's irrelevant in the scheme of things 26-Nov-20 11:36 AM https://www.youtube.com/watch?v=h9lbrr04XBQ 26-Nov-20 11:37 AM because of course he likes spirit 26-Nov-20 11:41 AM https://www.youtube.com/watch?v=iwj78pR46zM 26-Nov-20 11:51 AM The vast majority gets sold on to responsible parties who can possess them. Keeping Class 4 systems out of the hands of those who, in short, aren't is one of my responsibilities. 26-Nov-20 11:52 AM That's not the case here, stock is typically hoarded until it's scrap. The only groups that share are the ones physically beside eachother... 26-Nov-20 11:52 AM We have a university-wide site for giving stuff away / selling it / auctioning it, but it's not used with anything serious. 26-Nov-20 11:54 AM Which is a separate cranky of mine. It makes me sad when I see thing lying fallow, not being used. Pass that along and make room for a new project, PI. Don't just camp space with your derelict gear. 26-Nov-20 11:55 AM sheds a tear for every HPGe I've seen go into permanent storage 26-Nov-20 11:57 AM Now I need to pour more of Mama's Good Mornin' Holiday Bourbon to drown that sorrow. 26-Nov-20 11:57 AM cheers 26-Nov-20 12:13 PM it's noon! 26-Nov-20 12:15 PM Ah yes. Time to move on to Anderson Valley Winter Solstice beer. 26-Nov-20 04:04 PM that solder looks like wet dough ... sheared off 28-Nov-20 08:42 AM I was relieved when the optical breadboard I was asked to waterjet a hole in 28-Nov-20 08:42 AM Turned out to just be a plate with tapped holes 28-Nov-20 08:42 AM Rather than multiple layers of arbitrary honeycomb 28-Nov-20 06:31 PM I have no idea what will happen if you waterjet a honeycomb 28-Nov-20 06:31 PM Do the abrasives end up wearing transverse layers of honeycomb away 28-Nov-20 06:31 PM Are you gonna be left with lots of swimming pool for insects 29-Nov-20 01:18 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/PXL_20201129_211451614-25216.jpg 29-Nov-20 01:19 PM dusteh 29-Nov-20 01:20 PM I'm debating if I should demount it to clean it 29-Nov-20 01:20 PM If I do I have to realign it 29-Nov-20 01:22 PM why can't you clean it there? 29-Nov-20 01:22 PM I can 29-Nov-20 01:22 PM It's just I can do a really easy drag clean if I drop it out 29-Nov-20 01:22 PM Annnddddd someone has already scratched it up a bunch 29-Nov-20 01:22 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/PXL_20201129_212825791-51470.jpg 29-Nov-20 01:44 PM it looks... really easy to drag clean without popping it out? 29-Nov-20 01:44 PM it's not in a recessed mount 29-Nov-20 01:46 PM Geometry didn't quite work out, the wipe would wrinkle to much because of the surrounding housing 29-Nov-20 01:46 PM *did wrinkle 29-Nov-20 01:47 PM is it.. a fancy optic? 29-Nov-20 01:49 PM It was 29-Nov-20 01:49 PM But the coating has apparently been scratched off 29-Nov-20 01:50 PM then... do you care that much about wrinkles? 29-Nov-20 01:51 PM I thought it was still in tact when I started 29-Nov-20 01:51 PM I know better now 29-Nov-20 01:51 PM clean optic cleaning cloth folded with some methanol + being careful with your foreceps/whatever and it should be fine even if you apply some pressure 29-Nov-20 01:51 PM Like I wouldn't be so careless with a $500 beamsplitter, but it's just a $50 mirror isn't it? 29-Nov-20 01:52 PM It's a 0$ mirror now 29-Nov-20 01:52 PM I couldn't see how damage it was until I rinsed it off 29-Nov-20 10:47 PM https://en.wikipedia.org/wiki/22%C2%B0_halo 29-Nov-20 10:47 PM interesting view tonight in Southern California w/ one of those going on 29-Nov-20 10:47 PM did not know that was a thing and the optical background of it is really interesting 30-Nov-20 12:21 AM Oh neat, I think I've seen that a few times up here in Oregon too. 01-Dec-20 03:49 PM been playing around with laser-induced backside wet etching. Still fiddling with parameters...has a habit of going into thermal runaway mode and blasting holes through the glass but I think I can get it dialed in with some more tweaking 01-Dec-20 03:49 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/yakzQ7xytLiLTAeTscI2aZH-3jpLfvhXdK5qcu53Ld-314E7.png 01-Dec-20 07:02 PM @LRM that’s a micro ice particle effect. We see it here in Fresno a couple times a year 02-Dec-20 04:25 AM Is the myth that you should only clean coated optics with methanol true 02-Dec-20 04:25 AM I never know why people clean things with whatever chemical 02-Dec-20 04:25 AM On some AR coatings i used IPA and they retained their color so i was like idk imma just use the less poisonous thing 02-Dec-20 04:25 AM But others keep telling me to use ethanol or methanol only 02-Dec-20 04:25 AM Some others say acetone is okay 02-Dec-20 07:21 AM It depends on the coating and cement 02-Dec-20 07:21 AM As far as I know methanol will never be a problem 02-Dec-20 07:21 AM Acetone can be 02-Dec-20 07:24 AM Yeah I'd worry about acetone damaging coatings. 02-Dec-20 07:24 AM Much less methanol or ethanol 02-Dec-20 07:24 AM Of the two I'd use methanol the stuff you can get is likely more pure. 02-Dec-20 07:24 AM Getting optical grade ethanol here is hard 02-Dec-20 07:24 AM So all the common stuff has denaturants in it. And I doubt anybody wants bitterants and misc. ketones on their optical coatings. 02-Dec-20 07:43 AM Oh yeah, I’ve been told to only use spectroscopic ethanol or distilled water on diffraction gratings. 03-Dec-20 05:07 AM Ethanol is hygroscopic. And high purity undenatured reagent ethanol is hard to get sometimes if you’re at a university or big organisation. I don’t think MeOH is that dangerous, if you don’t drink it. 03-Dec-20 05:07 AM And high purity undenatured EtOH typically requires lots of government liquor excise or exemption paperwork 03-Dec-20 05:10 AM does it? 03-Dec-20 05:10 AM here you have to pay a lot of tax on it but apart from that it's just fine 03-Dec-20 05:14 AM Yeah you have to pay the tax, typically anywhere in the world I think. But lab users can get out of the tax if it’s for scientific use. 03-Dec-20 05:14 AM oh, ok 03-Dec-20 10:05 AM Methanol is the safe answer when you don't know what is safe, but a lot of coatings can also be cleaned with IPA or acetone And while apparently reagent grade stuff works, I've had issues with contaminants with HPLC grade stuff, so I wouldn't bother with anything below that personally. 03-Dec-20 10:52 AM And try not to bathe your hands in methanol. The skin soak through does add up. 03-Dec-20 11:02 AM Another thing I just remembered, while it's not always something you can do with optics, if you need your thing really clean, do a solvent series that goes from non polar to polar. Empirically you have fewer contaminants still on your surface when you do that order rather than the reverse. 04-Dec-20 03:55 PM Overly expensive beam shutter 04-Dec-20 03:55 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/image0-8EE7D.jpg 04-Dec-20 05:37 PM Mmm nice Q-switched Nd:YAG 04-Dec-20 05:37 PM Rotatable polariser? 04-Dec-20 05:37 PM Lovely clean optics bench 04-Dec-20 05:41 PM yeah he wanted to check circular, linear, and blocked 04-Dec-20 05:41 PM this was easier than adding a shutter 04-Dec-20 05:41 PM it's for the centrifuge 05-Dec-20 11:40 AM Laser-induced bubble formation and collapse at 30,000 FPS. 05-Dec-20 11:42 AM man that's pretty cool 05-Dec-20 11:42 AM need more fps I guess 05-Dec-20 11:42 AM yeah it's wild how fast it collapses 05-Dec-20 11:42 AM what kind of laser do you have? 05-Dec-20 11:42 AM and how reproducible are the bubbles? 05-Dec-20 11:43 AM i count ~6 frames, so bubble formation to collapse was ~200 microseconds 05-Dec-20 11:43 AM it's a 50w off the shelf galvo fiber laser (the kind for marking/etching metal) 05-Dec-20 11:44 AM oh so this is a thermal effect -_- 05-Dec-20 11:44 AM bubbles are super reproducible if you get the settings dialed in, that's a short clip of a whole string of bubbles down the line. But tweak the settings slightly and you get formation much more violently, or further from the surface 05-Dec-20 11:45 AM and how are you lighting the video? 05-Dec-20 11:46 AM yeah it's a copper sulphate + phosphoric acid solution. Laser vaporizes the copper sulfate, forms some copper oxide which adsorbs onto the glass slide (the thing right at the top of the frame) and next pulse heats the copper oxide even further (and is surrounded by a bubble of vapor which insulates it) 05-Dec-20 11:46 AM What I'm trying to get at, is if they are reproducible... you can get a higher framerate if you just do long exposures and use a fast light source which you scan in time.. Such as a laser 05-Dec-20 11:46 AM if you expose for 1ms but only have light for 1us, you just scan when the 1us happens and can get 1MHz video, etc. Same as we're doing with fs lasers and THz dynamics. 05-Dec-20 11:48 AM ahhh, i see. like strobe flash photography, but for video. iiiinteresting. 05-Dec-20 11:48 AM But it sounds like the effect is due to a ton of high rep rate pulses 05-Dec-20 11:48 AM rather than one strong one 05-Dec-20 11:48 AM so, jitter 05-Dec-20 11:49 AM yeah, it takes at least two pulses to get any explosion. If you dial it down to one pulse per point it just swirls the liquid around 05-Dec-20 11:50 AM can you trigger the laser to do just two pulses?? 05-Dec-20 11:50 AM i haven't discovered a way yet, no it's literally the worst software ever invented, which is probably pirated as well 05-Dec-20 11:51 AM Got any pockels cells? 05-Dec-20 11:51 AM if you can trigger pulses individually and have a pockels cell or other fast way to redirect pulses 05-Dec-20 11:51 AM you could use it for everything haha 05-Dec-20 11:52 AM nope! I'm an optics idiot, for the most part 05-Dec-20 11:52 AM googles 05-Dec-20 11:52 AM ahh i see. so you'd use one of those to alter the polarization, and presumably have a polarized filter/splitter somewhere to accept or reject pulses going into the solution (or wherever)? something like that? 05-Dec-20 11:57 AM Yeah 05-Dec-20 11:57 AM so you could send two pulses do make the bubble, and then at a variable delay later send a third for imaging... I say this with no knowledge about the laser you're actually talking about. 05-Dec-20 12:00 PM 1064nm, so it wouldn't be very friendly for imaging 05-Dec-20 12:01 PM doesn't have to be visible for imaging 05-Dec-20 12:01 PM hehe fair 05-Dec-20 12:01 PM there is an SDK for the software. if it works, theoretically it'd allow much finer control of the laser. Looks like you can tell it to mark specific (x,y) coordinates, specify number of pulses, etc. Still unclear how much control the software has over the hardware though. E.g. if you set the laser to 20khz, and tell it to do a single pulse... does that end up as one actual pulse, or just one pulse "command" and you get as many pulses as you get based on the hardware at the specified frequency and phase of the moon 05-Dec-20 12:01 PM ‍♂️ 05-Dec-20 12:01 PM maybe i'll just have to build my own someday instead saw a nature protocols paper the other day for building a femtosecond fiber laser for "cheap" 05-Dec-20 12:01 PM heh, here's what happens when you dial the power up too much (only 5000 FPS, to get a wider shot) 05-Dec-20 12:19 PM Oooh that's neat! 05-Dec-20 12:19 PM "building a femtosecond fiber laser for cheap" 05-Dec-20 12:19 PM I wonder what is their definition of cheap 05-Dec-20 12:22 PM Based off of what I know from the group that has made two here...cheaper than a Ti:Sapp but not remotely actually cheap. 05-Dec-20 12:22 PM Not surprised 05-Dec-20 12:22 PM new tisaph rods are like 10k 05-Dec-20 12:22 PM slivers, that is 05-Dec-20 12:22 PM you don't get much volume 05-Dec-20 12:24 PM Assuming it's q-switched, it should just be one pulse, but that's speculation. 05-Dec-20 12:24 PM And hmm, fiber doesn't actually sound cheaper then 05-Dec-20 12:24 PM Maybe if you already have all the fiber equipment 05-Dec-20 12:24 PM But... 05-Dec-20 12:24 PM Yb:Fiber does make a better frequency comb than Ti:Sapp if you're masochistic enough to do that though 05-Dec-20 12:34 PM @SleepyOwl Joyce iirc, it was like <$10k USD for materials.... which honestly was a lot less than I expected. But it was like $80k in necessary equipment (fiber fusion splicer, etc) 05-Dec-20 12:34 PM Ah 05-Dec-20 12:34 PM That would be cheap for a femtosecond laser 05-Dec-20 12:35 PM https://www.nature.com/articles/s41598-019-40871-5, prices are in the first Supplemental 05-Dec-20 12:35 PM looks like i exagerated... just $50k in equipment not 80 05-Dec-20 12:46 PM soooo many neat things you can do with a femto though... i wish i had the skills (and wallet) to build one. maybe someday 05-Dec-20 12:55 PM Wow, they used a really, really nice fiber splicer 05-Dec-20 12:55 PM You could pretty easily get away with one much cheaper than that 05-Dec-20 12:55 PM Still like ~10k 05-Dec-20 12:55 PM But that's better than $35k 05-Dec-20 12:56 PM oh, interesting. probably more likely to find one second hand too, if it's cheaper 05-Dec-20 01:02 PM Probably yeah. I don't know if it's a good one because I don't work with fiber ever, but the T-400 from Sumitomo is under $3k 05-Dec-20 01:02 PM And it's still a fusion splicer with things to help you get a good splice 05-Dec-20 01:04 PM this is not helping my desire to build one luckily... my lack of knowledge makes me think it's a bad idea, and i should start on something simpler first 05-Dec-20 01:05 PM Always happy to be a bad influence! 05-Dec-20 01:06 PM general laser question: why would one prefer a freespace laser over fiber (for the output that is)? Fiber just being more convenient to get where it needs to go? 05-Dec-20 01:07 PM iirc fiber stretches your pulses, has losses and is worse for phase coherence 05-Dec-20 01:07 PM but I'm really no laser guy so take it with a grain of salt 05-Dec-20 01:09 PM That sounds about right 05-Dec-20 01:09 PM The main benefits AFAIK is that thermal lensing isn't as bad so you can make a laser out of suboptimal transitions 05-Dec-20 01:11 PM ah ok, that all makes sense 05-Dec-20 01:33 PM Fiber can’t handle my intensity 05-Dec-20 01:33 PM stretching your pulse isn’t usually an issue, because you can just impose the correct chirp initially 05-Dec-20 01:33 PM I think it was Donna stricklands first cpa 05-Dec-20 01:33 PM Where the fiber they were using to stretch it 05-Dec-20 01:33 PM Broke in half 05-Dec-20 01:33 PM But luckily it worked even with only half the dispersion 05-Dec-20 04:04 PM The chirping is a good point I didn't think of, you can basically always deal with pulse broadening, but the intensity thing is curious to me. I guess thermal lensing isn't typically a big deal in ultrafast, but I thought the big reason to use fiber is that you can get really long interaction areas and that thermal lensing isn't a big deal until you get to seriously high powers because you just get a beam that diverges a bit more or less depending on the details of the laser. Though I guess I also hear that femtosecond pulses are short enough that thermal lensing tends to not matter anyway. Would your pulse quite literally just damage the fiber if you used it? 05-Dec-20 04:04 PM And I guess there's not a particularly compelling reason to use bare fiber for most applications 05-Dec-20 04:13 PM Not a big deal but thermal effects aren't something you can entirely ignore either. While the average power may not be high, the pulse peak power can quite rudely delaminate coatings if your angles are a bit off or burn through fiber cladding. 05-Dec-20 04:22 PM thermal lensing in femto systems is mostly an issue with the pump beams 05-Dec-20 04:22 PM if the pump changes enough that the lensing in the crystal changes 05-Dec-20 04:22 PM then the femto pulse can focus in the crystal 05-Dec-20 04:22 PM and it burns it instantly 05-Dec-20 04:22 PM My laser burns thorlabs protected silver mirrors, the p01 coating 05-Dec-20 04:22 PM we have to use dielectrics and even then the beam is bigger than we'd like 05-Dec-20 07:25 PM Yes, that. Thank you for wordifying more betterer than me for @Mezmorizor. 05-Dec-20 07:30 PM your favourite company "not infrequently" damages and has to replace their own crystals this way 05-Dec-20 07:30 PM only in research labs that negotiate "better specs" that really amount to just running the system at 99.99% capacity rather than the regular 90% 05-Dec-20 07:48 PM [angryfist] OPTIC MURDERERS! 05-Dec-20 08:08 PM they gave me the burnt mirrors though 05-Dec-20 08:08 PM because they can be re-used when rotated 06-Dec-20 01:53 AM The Mirrors from Thorlabs have a really low damage threshold, buy mirrors from Laseroptik GmbH those are the best i worked with. 06-Dec-20 09:05 AM @verschrottix I don’t see the damage threshold on their website? We have enough vintage CVI stuff to work with though. Our beams are 17mJ/150ps/3mm and 13mJ/170fs/8mm 06-Dec-20 09:15 AM AFAIK Laseroptik is a "designer coating" company 06-Dec-20 09:15 AM They have extras of batches other people ordered sometimes, but they're more about making an optic for your specfic application 06-Dec-20 09:57 AM UV or mid-IR wavelengths you can’t transmit in fibre? 06-Dec-20 10:06 AM We usually run Ekspla Nd:YAGs in external sync mode so we have manual electronic control over the pulse train. Rising edge fires the flashlamp, falling edge fires the Pockels cell. Easy to just generate any pulse waveform you want from AWG or FPGA etc. You just have to keep the Q-switch delay within safe levels since it’s manually controlled by the high period. 06-Dec-20 01:16 PM This seems nonideal when you have hundreds of mirrors haha 06-Dec-20 02:24 PM Oh yeah. I don't think anyone in the research side of the world consistently uses custom optics like that. I think their bread and butter business is people like coherent who could plausibly need 100 custom high reflectors ASAP 06-Dec-20 03:34 PM re-measured the available space in the toolmakers microscope to possibly slide a camera in, and I think it is just big enough, and alsi I would be somewhat comfortable modifying the ledge profile some to fully get the target camera+lens inside - just need to ensure all the chips come out! 06-Dec-20 03:34 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/DSC_2330-51D66.jpg 06-Dec-20 04:06 PM the other parts of the system, beyond a mount and lens for the camera in the hole, would be like an rpi server that does the actual computing, and a tablet as a screen+interface (via web, not a custom android app, to the rpi) to mount in the front 06-Dec-20 04:06 PM maybe Nvidia Jeston Nano? 06-Dec-20 04:06 PM oh, appears to have no embedded wifi or bluetooth, interesting 06-Dec-20 05:15 PM At my company we like to use laseroptik and layertec for high quality coatings 06-Dec-20 05:41 PM layertech and semrock have really nice beamsplitters 07-Dec-20 03:12 AM Anyone ever used infrared lamps for bakeout? Is there any concern with inhomogeneous heating stressing and cracking/causing leaks in glass viewports and flanges? Is it effective in general? 07-Dec-20 08:15 AM I thought you wanted UV lamps 07-Dec-20 08:15 AM not IR 07-Dec-20 08:15 AM https://avs.scitation.org/doi/10.1116/1.4754292 07-Dec-20 12:10 PM @funranium do you have an idea how the ultrafast people there deal with the reflections off lenses, even AR coated give quite a bit back and always trying to block with apertures is tedious 07-Dec-20 12:11 PM Tedious but necessary. 07-Dec-20 12:16 PM How does that work in pulse shapers ? 07-Dec-20 12:16 PM Do they actually have those fancy rectangular apertures? Or just box it? 07-Dec-20 12:18 PM Box where ever you can 07-Dec-20 12:19 PM Boxes are only useful when they’re closed. 07-Dec-20 12:24 PM Ugh, you are asking the hard questions. 07-Dec-20 12:26 PM I just hate these things 07-Dec-20 12:26 PM You attenuate it until you can’t see it 07-Dec-20 12:26 PM Put ND 6 07-Dec-20 12:26 PM And it still burns a pixel on your alignment-checking webcam when you focus it with a 30cm lens 07-Dec-20 12:26 PM Checking with a phosphor viewer? Looks cartoonishly radioactive 07-Dec-20 12:28 PM And I assume you have minimum power requirements for your pulse shaper that won't let you get away with low power operation. Because that's always the problem. 07-Dec-20 12:28 PM Yeah, the more power you use the looser you can focus and so the faster you collect data 07-Dec-20 12:28 PM To do the experiment once you only need like 50 photons right? But naturally once isn’t enough. So if you’re doing it millions or billions of times... 07-Dec-20 12:28 PM The optimum of less power = more stable laser = less downtime 07-Dec-20 12:28 PM Is at least a situation where you can optimize without just approaching zero power 07-Dec-20 12:57 PM @idmb whats the difference between using uv and ir for bakeout 07-Dec-20 12:57 PM There are plenty of companies selling ir lamps for uhv bakeouts, never heard of uv lamps until you pointed it out 07-Dec-20 01:01 PM IR lamps are just being used as heaters 07-Dec-20 01:01 PM UV has an actual mechanism for getting the water out of the metal 07-Dec-20 01:01 PM I don't know anyone that uses IR for bakeout but it looks like the point is just more efficient heating of the interior of the chamber, and easier installation. (Compared to plates / tape) 07-Dec-20 01:01 PM IDK. bakeouts give grad students some much-needed vacation time 08-Dec-20 11:37 PM I’m looking for some glasses. Cheap yet reputable, comfortable and easy to wear over my normal glasses, OD7 1064nm. Was looking at Thor LG1 but please feel free to suggest any other vendors you like? https://www.thorlabs.com/thorproduct.cfm?partnumber=LG1 09-Dec-20 01:30 AM Hahaha “if it’s open-source then it’s up to the builder to add it” oh dear. (“it” = interlocks, shielding, shutters or emission indicators on a class IV laser) 09-Dec-20 05:37 AM :X Yikes. 09-Dec-20 07:57 AM I am very fond of Laservision as being decently priced and willing to work with you on weird stuff. Their search tool will do you right. https://www.lasersafety.com/product-category/eyewear/ 09-Dec-20 10:00 AM Hahaha. Laser vision. I’m off to the card room! See ya suckers later! An hour later at the card room and the whole deck has been set on fire.. gee that never happened in the trashy spy novels?!?!? 09-Dec-20 10:00 AM Ok inner 13 year old reading comics has been indulged for the day. 09-Dec-20 07:52 PM heh 09-Dec-20 07:52 PM the visually ~1" beam (really about 1.5cm) from my laser 09-Dec-20 07:52 PM if I let it travel ~20m 09-Dec-20 07:52 PM is like 10" 09-Dec-20 07:52 PM nice collimation, spectra physics. 09-Dec-20 07:52 PM do people normally just not send them far, or continually play with lenses ? 12-Dec-20 09:23 PM so im trying to make a 2d mot and i want to mount a piece of silicon on a blank flange to act like a mirror of sorts in about 10^-8 mbar. is the best way to go about this using torrseal? 12-Dec-20 09:23 PM and whats the best way to get a hole in the silicon? 12-Dec-20 09:23 PM i feel like its just gonna cleave if i do any sort of drilling 12-Dec-20 10:03 PM Could it be clamped? 12-Dec-20 10:12 PM I am unfortunately not someone who knows anything about silicon and making holes in it but suggestions for the best methods might depend on the size of the hole you are trying to make...? 12-Dec-20 10:12 PM If you are considering drilling it sounds fairly large 12-Dec-20 10:13 PM I think i wouldnt be opposed to tapping a hole into the blank flange, but is it easy to produce a hole in a silicon wafer? 12-Dec-20 10:13 PM To clarify, i want to make a hole anyway for the atoms to pass through it 12-Dec-20 10:13 PM For the 2d mot loading into a 3d mot 12-Dec-20 10:13 PM It will probably be a few mm 12-Dec-20 11:56 PM Making a hole in a wafer of Si sounds like a pain 12-Dec-20 11:56 PM How big diameter? 12-Dec-20 11:56 PM This reminds me of trying to cut a circle from a Si wafer... didn’t work well. 12-Dec-20 11:56 PM Blow a hole in it with Nd:YAG ? Or, hard mask and DRIE all the way through the wafer if you have access to one 12-Dec-20 11:56 PM Or FIB all the way through? 13-Dec-20 04:37 AM Hard mask + Hot KOH etch will get you through a .5mm wafer overnight, wont be a circular hole though and it will have angled sidewall but at few mm the angle wont be super noticabe. Will also need to protect backside of wafer, ProTEK B3 is what I've seen used for that. 13-Dec-20 04:37 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/aaaaaaaaa-ABF7F.png 13-Dec-20 04:37 AM DRIE and FIB like @a_quiet_scientist said work too, but I don't know what you have access to 14-Dec-20 04:50 PM FIB through a wafer is basically crazy to hope to get done 14-Dec-20 04:50 PM Unless maybe it's a plasma FIB 14-Dec-20 04:50 PM Mayyyyybe 14-Dec-20 04:50 PM The scale they are good for is just significantly smaller 15-Dec-20 08:57 AM we don't happen to have any digital holographic microscopy experts in here, do we? 15-Dec-20 11:51 AM unst, the camera I was looking at, there were 3 of them, got th e seller to measure a bunch for me - all sold recently, likely to one buyer 15-Dec-20 11:51 AM there's another with a whole bunch of lenses up, but yeah, they pop up here and there, just usually not many within the US 15-Dec-20 03:49 PM @polyfractal I've been working with high volume hologram manufacturers lately 15-Dec-20 03:49 PM My work is going to production now 15-Dec-20 03:49 PM To a total of like 65 million square inches of film being embossed 15-Dec-20 03:49 PM I want to play with this technique next 15-Dec-20 03:49 PM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/fabrication_of_rainbow_holograms-98441.pdf 16-Dec-20 04:51 AM hm is that using crosslinking of the PMMA or the breaking? 16-Dec-20 04:51 AM in the paper I mean 16-Dec-20 04:51 AM (ok, should more then cross read it ) 16-Dec-20 04:51 AM trying to do similar stuff, but only simple gratings and waveguides 16-Dec-20 04:51 AM and some electrode stuff via electroplating - but I'm a litho noob 16-Dec-20 06:19 AM well that's pretty nifty 16-Dec-20 06:19 AM and a lot of square inches! 16-Dec-20 06:32 AM how many football fields are that 16-Dec-20 10:40 AM @N00N usually you're breaking PMMA (chain scission), forming new ones is usually not the standard and requires more beam time (thus more money to expose a given area) 16-Dec-20 10:40 AM @polyfractal looks like almost 8 footballs fields :p 16-Dec-20 10:50 AM yeah, more dosage for crosslinking 16-Dec-20 10:50 AM tried both - but crosslinking only for low resolutions 16-Dec-20 11:00 AM How do they do the high volume hologram production? Is it like roll-roll stuff? 16-Dec-20 11:16 AM but I only need mm^2 not football fields 16-Dec-20 11:16 AM (I've no idea about high volume hologram production) 16-Dec-20 11:16 AM only got triggered by the ebl paper - 'cause I'm experimenting with that kind of stuff 16-Dec-20 12:14 PM @mike crb yep, roll to roll! Take my original 1 inch square e-beam litho, sputter silver layer, electroform thick nickel backing/substrate. Peel off from photoresist+silicon, clean residual resist from metal. Recombine (stamp) into UV photopolymer to make a larger stamper, recoat seed layer, grow nickel backing... Repeat this "recombination" until the stamper is 2ft square, put onto roll to roll machine, feed film through 16-Dec-20 12:53 PM "larger stamper" ️ 16-Dec-20 02:20 PM That's awesome, roll to roll is so cool. 19-Dec-20 08:16 AM optical design in fusion... not ideal hah 19-Dec-20 08:16 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/unknown-C08C9.png 19-Dec-20 09:15 AM If it’s only 2D, you could get optgeo 19-Dec-20 10:04 AM the optical bit is actually super simple, needed to CAD up the housing and flexures so I could print them 19-Dec-20 10:04 AM but optgeo looks nifty, gonna play with that some 19-Dec-20 11:32 AM optgeo is terrible to use but pretty powerful 19-Dec-20 11:32 AM it was useful for doing a pulse shaper where we just wanted to check clearances and stuff... because it'd be like 8 napkin math calculations 21-Dec-20 06:56 AM anyone have experience with el cheapo Aliexpress stages? Contemplating picking up a bunch for crude alignments since they are so cheap: https://www.aliexpress.com/item/32845289892.html 21-Dec-20 07:40 AM I also ordered some 21-Dec-20 07:40 AM will arrive january 21-Dec-20 07:40 AM if world is not ended 'til then 21-Dec-20 09:41 AM I wanted some but PI said he didn't even trust the mcmaster ones 21-Dec-20 09:41 AM And so... we have a stage shortage. 21-Dec-20 09:48 AM haha 21-Dec-20 09:48 AM welp 21-Dec-20 09:48 AM i figure as long as it doesn't creep and the micrometer/bearings are even remotely smooth it'll do the job 21-Dec-20 09:48 AM for the janky stuff i do at home anyway 21-Dec-20 10:34 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200716_194350-4299C.jpg 21-Dec-20 10:34 AM wheeey:D 21-Dec-20 10:34 AM Vacuum%20Hackers%20-%20Text%20Channels%20-%20lasers_and_optics%20%5B597249360622780426%5D.html_Files/IMG_20200401_183919-C1360.jpg 21-Dec-20 12:36 PM i have no idea what that is... but it looks fragile and scary 21-Dec-20 12:50 PM Big diode bar, probably 808 nm and 50W+? 21-Dec-20 12:53 PM this one is a 50W 808nm from Jenoptik 21-Dec-20 12:53 PM this one 975nm 40W from LIMO