Building a Solid State Laser - Pt. 1

[@DOGMA1138]

No updates? :(

[@EricThornton24]

Yes updates! :) kzbin.info/www/bejne/rHSWh353ptOqf6c

[@AppliedScience]

I really like your style, and just watched all of your videos. Keep up the great work! Also, I really appreciate the shout-out. Let me know if you need any parts.

[@EricThornton24]

Dude! I've been following your channel since seeing your SEM project in MAKE 'zine, however long ago that was... You were a major inspiration for me getting into not only KZbin but engineering in general. So, thank you for sharing your work and for taking the time to have a look at mine - it means a lot!

[@Rock57811]

Well, the fundamental error you did make is that you needed to check if the side of the Nd:Glass Rod are coated, to reduce the internal reflection. Normally Nd:Glass has an optical density of around 1.52 so regarding to the fresenell equation you have 4% of losses on each side of the rod. So you would need to pump to high to at least have more than 8% gain (in perfect alignment ). The old russian systems did not a very good job on coating because they simply used more pumping power (like most russian designs). The next Misstake you did was to estimate the 80% output coupler. This does work fine for Nd:Yag, for Nd:Glass you have factor 10 Less stimulated emission (Laser Book by Knebühl & Sigrist), so a calculation would be needed. I did an Excel sheet for that, depending on the Pump power and absorbed energy you might go for a 96% mirror. The Nd:Glass does have its stimualted emission around 1060nm due to the nephelauxetic effect, Nd:Yag has it at 1064nm. Next Error, i would never, really NEVER go for a plane parallel resonator, i personally recommend the confocal since the adjustment is much more easy. I somekind of made the same misstakes when i started :-)

[@patrykk1709]

Could you share this excel sheet? I'm really interested how you calculated it

[@Rock57811]

@@patrykk1709 sure / email?

[@cxn8]

Confocal is really not ideal for Nd:Glass. Plane-parallel is typical for solid state, in particular Nd:Glass and Nd:Glass lasers, because it avoids creating hot-spots in the rod.

[@brianthurston8194]

I built a DPSS (diode pumped solid state) ND:YAG laser a few years ago and also had some trouble getting it to lase. I had 2 problems, insufficient pumping light, and a poor choice of mirrors. Initially I assumed that both mirrors in such a laser should be flat. Despite much effort this setup did not work. It is possible to make a laser work with two flat mirrors. However, the laser will be much more stable and easier to align if at least one of the mirrors is concave with a radius of curvature greater than the length of the laser cavity. Once I started using a concave total reflector I was able to get the laser operating in a few minutes. However, my laser operates continuously and with yours being pulsed it may take you a while to find the sweet spot. An autocollimator would be helpful for alignment, although they are expensive. I also was able to make my life easier by using the smallest ND:YAG rod I could pump with my diodes. The smaller the lasing medium the better your chances of reaching threshold. Here are the parameters of my laser: Cavity length: 180mm Output coupler: flat 20% transmission (from eBay, works great!) Total reflector: concave 100mm focal distance (radius of curvature 200mm). I also had good results with a 1000mm focal length mirror. Both from ThorLabs. Pumping power: 54 watts at 808nm Output power: 13.5 watts I'm curious to see where you go with that capacitor bank. At work I use pulsed capacitors of several kilojoules for metalworking and other applications. I'd love to see current and voltage waveforms from the discharge of your bank. Good luck and use the one hand rule around capacitors! And don't skimp on laser glasses! Out of curiosity I bought some cheap ones on eBay that were 'rated' for 1064nm and my laser went right through them!

[@knglaser]

I've built a ruby laser at a similar size. The one thing I see you are missing is the inductor in the PFN. Otherwise you'll not get the pulse spread out enough and go into UV and also the plasma will get opaque. I used a quite large air core inductor, I think it was about 100uH with 2.5mm2 cable. I used the pfncalc1.xls from sam's laser faq. Also, you will need to adjust the mirrors with the rod in place, the surfaces on the rod could be at a slight angle and this will mess things up. I used the same technique and got some sort of interference. A small low powered HeNe is better for this and should preferrably be single mode.

[@paoloh885]

I just started a laser welding project for my internship and this really helped me get an impression of how a solid state laser works. I don't know what your job is but you could be a good teacher!

[@WoodenWeaponry]

Holy cow, this is high quality.. Thanks so much that you took the time to make this video not only good but excellent!

[@shadowknight7584]

Agree

[@WagonLoads]

You said that the best reflective surface for the mirrored tube inside is gold. I would suggest that you look at videos on vaporized aluminum mirrors for parabolic telescopes. If they can vapor coat glass with aluminum, you should be able to vapor coat gold onto the inside of your aluminum chamber... It is something like electro-plating in a vacuum or near vacuum, using a pressure cooker as vaporizing chamber. Hope it works..

[@seasicksinbad]

May the KZbin gods bless you with bunches of views and subscribers. I can't thank you enough for this very informative and fun video.

[@christopherleveck6835]

More importantly the laser tube gods...

[@fjs1111]

Eric: Good work my friend. 2 things.. 1) The likely reason you didn't get an interference pattern in alignment is because the alignment laser was not coherent enough. Some diode lasers and high quality helium are best. In your case, you did it right.. 2) The flash tube: Quartz is good, but Borosilicate is better for passing all spectrum Hope this helps!

[@Dwarfracer88]

If there is a chrome plating company in your area take your chamber to them and have it copper plated. They use copper as a sort of filler to be able to polish the part to be chrome plated to a very flat and smooth surface so the chrome looks really brilliant. You could then polish the interior to a brilliant shine in copper to help the wavelength reflection you are looking for. It's pretty cheap as well.

[@excitedbox5705]

gold or silver electroplating can be done with qtip and battery

[@whatelseison8970]

I love everything about this video. I was working on my crappy webcam spectrometer project and finding this peak at 810-ish nm coming from my green DPSS ebay laser and thinking, 'Don't these things usually leak 880 nm pump light? I better remind myself how these things work." Turns out I was wrong, my crappy spec was almost right, and after watching a super boring video confirming that I stumbled upon this _serendipitous_ treat of a video. Crazy how the peak I was detecting was actually at 808 nm just like that Xe peak you mentioned in the video... Spooky.

[@terence79chan]

Thanks for the treat! One of the best videos that documents the steps of making of a Solid State Laser!

[@christopherleveck6835]

Solidish state laser?

[@bobscott1315]

I would suggest that the flash tube be CLEAN. I used to work in an instrument shop for a university chemistry department. For any type of fairly high energy lamps we would wear a NEW (each time) pair of cotton gloves we handled flas tubes, and clean them with alcohol and lint free cleaning wipes. Otherwise when the tube flashed could explode from localized thermal energy from the oils from skin burning off. As a question, seeing your laser rod, it has a surface finish that is not very transparent. Could that be a cause of not enough energy transfer to make it not work?

[@macpr0c]

Oh man this was very enjoyable, I loved that you took the time to explain the concepts and details of the design process and problems that have arisen. Your way presenting reminds me of Marco Reps and thats a homerun in my book. I'm excited what future videos you will produce on this project and more, best of luck to you!

[@byronwatkins2565]

First, if the rod ends are perpendicular to the rod's axis, then reflections from the rod ends will form additional resonant cavities; it will then be fairly impossible to bring all of the cavities into resonance simultaneously. Typically, the ends are polished at 88 deg. from the axis so that these reflections immediately leave the cavity. Second, refraction at the rod ends requires that the initial alignment be performed with the rod in place. Third, copper sulfate in water could be used to plate the elliptical mirrors in copper rather cheaply. Fourth, planar end mirrors form an unstable cavity; a confocal cavity using spherical mirrors would be a much wiser choice. Fifth, it will probably be necessary to cool the elliptical space with distilled or DI water if more than a few pulses at a time are desired. Sixth, capacitors can be charged in parallel and then connected in series before discharging; this might solve 2-3 of your problems.

[@Aslyuriel]

Damn, This is a super high quality video, Subbed for sure. Looking forward to part 2.

[@blackdeathghostye6654]

Most underrated channel out there

[@markleightonson1770]

As a kid in the 60’s, I wanted to build a laser - the Kodak ruby rod was $119. The Xenon flash tube was used. I couldn’t affford the ruby rod with mirrored ends (one half mirrored).

[@quidem666]

I also build lasers. I never made it work. No laser light came out no matter what I did. Finally I tried to insert an inductor in series with the capacitor bank and it did the trick. If the light pulse is too short, there will be no laser light. I'm not saying that's what's wrong with your laser but it could be. That the lamp exploded at such low energy may be due to a far too short discharge time. I use an OC mirror with only 30% -T. It works but I have no idea what is optimal. I have some short video clips on my old laser in acction but I am building a new one, much bigger (because bigger is always better) So if you have more tips and ideas I will be happy to accept them. You have made a very good video. Educational and interesting. I'm waiting with excitement for part two.

[@3rdworldtrillionaire46]

You might be facing a problem with the heat generated, eventually the aluminum base supporting your mirrors might expand and bend, bringing the mirrors out of alignment.

[@maxmustermann5353]

Cool project! If you have problems with insulation of your high voltage stuff, try putting some PTFE around it. PTFE or Teflon as it's known for, is a very good insulator. You could try some Teflon tape used for piping.

[@MethelinaPills]

Hello there! Nice job! Hope it helps/ Some info about "GLS-1": The cross section of the stimulated radiation 1.7E-20 cm^2 Refractive index at the wavelength of radiation 1.521 The absorption index at the wavelength of the radiation. 2E-3 cm^-1 Concentration of Nd ions. 1.9E+20 cm^-3 Luminescence attenuation time. 390E-6 sec Quantum luminescence output 0.78 The population of the lower laser level, ions 6.84e+015 cm^-3 The wavelength of the radiation - 1064 nm XD

[@SarahKchannel]

You need to be careful with the xenon tubes, touching them with bare hands leaves residue, that even when cleaning remains in the glass structure. When running the tubes at this powers, this produces hot spots on the surface and can lead to spontaneous dismantling of the tube...

[@soulvagabond]

Agreed, my memory from the childhood, when I was trying to source some Russian parts for a diy laser, for the flashtube, I clearly remember the note to avoid touching it with the bare hands or it will explode.

[@darkshadowsx5949]

5 months later and no part 2 yet? i like how you demonstrated how to make all the light reflect onto the laser rod.

[@jacobv_]

Cool project, can't wait to see part 2

[@UNVIRUSLETALE]

This is a really well made video, can't tell much about the laser as I despise optics with all of myself with some ptsd post exam but I'm looking forward to how this laser evolves

[@hzpower745]

you can place the rod on its end on a cert. flat piece of marble and with simple machine tools ... a parallel and calipers measure between the marble on one end and the parallel on the other in a few directions and get a very good idea if the ends are parallel

[@JPMontello]

I love this video! I'm excited for part 2! I really like your aluminum pump chamber, it looks super nice. I plan to 3d print a mold for my laser pump camber and cast a chamber out of plaster or other white ceramic. Fun fact some white ceramics will reflect more light than a really nice metal mirror! Also ceramic materials will help insulate the flashlamp from high voltage.

[@akkudakkupl]

I know this is old, but mill oring groves in the end plates to hold your flash lamps instead of having them lay on aluminium, it might be that the tubes got damaged because of uneven thermal transfer on one side of the glass (touching metal). EDIT: fixed a typo - there was 'hot' instead of 'got' ;-)

[@sashablfc]

Very nice mate, is there any updates on this yet?

[@peterzeboroff7448]

Hi, I am also a very big laser enthusiast and I have been playing around with and building lasers for close to 50 years now, although my main type of lasers are the high power visible ones. I too am playing around with the idea of building a fairly high power solid state laser but I am interested in the Ruby lasers mainly because of the fact that they are in the visible red. In some of the research that I have done in the past few decades I have found alot of various forums and laser groups that discuss all the various parameters and the required parts and their specs and one reason your flash tube may have exploded is because of something called ringing and overshoot. If the power supply that is triggering the flashtube isnt built or set up correctly, when the pulse is triggered The energy stored in the capacitors sends a something like very jagged spikes which produce a very quick shockwave inside the flash tube which either greatly shortens the life of the flashtube or many times, the flashtube will explode much in the same way that yours did. Some of the builders use various types of chokes inline between the flashtubes and the capacitors which if made correctly will produce the extremely quick microsecond pulse that is required to start the lasing process but the choke dampens the current and prevents those destructive shockwaves inside the flashtubes. I am certainly no expert in this either but from what you stated in your video, I think that you should definitely look into what I have said here. I really hope that you are ultimately successful as that will give myself much more hope in my endeavours. I think in the laser pointer forums, there are at least a couple of guys there that have offered to help people in designing a solid state laser such as this, it would be worth a look there. Good luck.

[@Daedronus]

Use barium sulfate on the cavity walls, for pulsed yags 80% OC is way too high, you need something like 60%, or lower, DPSS yags use 80%+

[@Northerncalwolf]

Bit of nerd fodder for you -- Krypton generates light more on the red side of the spectrum. *Most* krypton flashlamp tube walls are thinner than Xenon flashlamps. If you are using a Xenon flashlamp, no water jacket is OK for low cycle pulse counts. The thinner Krypton tube walls were designed to take advantage of the hydrostatic properties of water/ "you cannot compress a liquid". The thinner wall material meant that higher energy amounts could be put into the lamp and more flashlamp energy could be transmitted to the rod and allow for more efficient heat removal. What you buy on Fleabay is what you buy on Fleabay!

[@odissey2]

One problem, among others, the Nd:YAG has very narrow absorption spectrum near 808nm, which is responsible for 1064nm output. The flashlamp, however, produces very broad output spectrum spreading over several hundreds nm. Any radiation outside 808nm (+-2GHz) is being lost, going into the heat. For that reason, narrow-band IR diodes at 808nm are used instead of the Xe lamp. Secondly, the relaxation time of Nd+ is ~200us, so flash duration should be preferably under 100us short to concentrate the pump energy in time. Without the thyratron, the Xe lamp was likely producing ms-long pulse. Finally, the 1064nm radiation is not visible by naked eyes, so some detector should be used to confirm the single shot, the "magic paper" won't help. I hope that you can now appreciate Dr. Theodore Maiman's achievement after all and recollect his name.

[@CHALLENGER3000]

Love the simple way of explaing. Also love the quality, its not easy to structure and produce it this way, respect. Sub well earned. (:

[@TheAtomstrike]

Hello. I work professionally with Candela and Sciton cosmetic lasers. I want to tell you that if aluminum is plated with silver, then the reflection will improve.

[@alexoja2918]

You can polish aluminum especially with alkaline substances, but it'll accumulate a new oxide layer.

[@sebastianmuller1210]

Aligning the mirrors perfectly is critical otherwise the "amplified stimulation" part in lASer is missing. Right distance and parallel. So getting those interefernce rings is the critical way to go to get the laser going.

[@stevenw4549]

I think the frosted tube is blocking too much light from the flash tube. I also saw one made like that a long time ago and it had a more pronounced elliptical. Have you thought about using a rod with a liquid core? You could circulate the liquid for cooling. I was wondering if you placed the liquid rod inside a larger tub and created a vacuum then with high voltage applied when the vacuum reaches a high enough degree of vacuum the vacuum tube should flash. Put the whole assembly in a reflective tube and of course mirrors each end like you have.

[@screamingwilson]

You could try gilding the cavity with gold, copper, or silver leaf.

[@screamingwilson]

Or you could try electroplating although gilding is easier.

[@danbrit9848]

you have inspired me to start the road to my own yt ...ive always wanted to...but your success in short time inspires

[@tehpwnerer6821]

Really liked your video. Good audio quality, perfect mix of information and entertainment plus useful links in the description . I usually don't subscribe to channels all willy-nilly, but i wanna see part 2 (even if i have to wait 6 more months for it). Only one little thing annoyed me: a 18 seconds intro is way to long, i almost skipped over this gemstone.

[@kurjibhalsod3547]

And after 6 months, when second part will release?

[@Deadwindshadow]

What a awesome new channel!!! You deserve like thousands more viewers what a shame I look forward to the update on this laser!

[@hullinstruments]

Jesus dude this is a great video! Hope you make more optical and laser content soon!

[@aquahoodjd]

Hey - if yout not using that laser I may have a use case for your tiny ablation laser. I would like to electronically steer the beam to create both microfluidic channels and photonic chips from borasilicate glass/ crystal?

[@MrBleulauneable]

Edit: I've had a quick look around about the alignment of laser cavities like yours and it seems that getting an interference pattern isn't always critical and you should mostly be concerned about the position of the dots. So the rest of my comment which was about optimising that interference pattern might be useless. The alignement of the cavity is equivalent to aligning an Michelson interferometer which is a procedure that is widely thaught so you should be able to find decent info on how it's done without too much trouble. Some suggestions : 1) You probably need to double check on the laser you're using. You're trying to make an interference patern from beams that have an optical path difference of around 50cm (twice the cavity length), but typical HeNe lasers have a coherence length of 20cm (meaning that if the second beam travels for 20 cm longer than the first one the interference patern will start to disappear but I'm not sure how fast it goes away). In principle for this measurment you'd need a single frequency HeNe laser or a stabilized HeNe laser (wich I believe are the same) or any other laser with a coherence length that is more than 50cm (or equivalently a linewidth that is below 600MHz). 2) instead of looking at the beam on a card placed on the laser itself you could put a 50-50 beam splitter at 45° (an economy beam splitter is 30$ on thorlabs) on the laser path to look at the image outside the axis of the laser (note: depending on the beam splitter you use it will create a secondary beam offset from the first one due to reflections inside the beamsplitter wich may can be an issue if you pattern has low contrast to begin with) 3) you could use a lens to expand the beam of your laser in order to maximise the size of the pattern

[@One-jz6sl]

I thought there had to be an inductor in series with the capacitor voltage output to limit the current, otherwise the flash tubes will explode.

[@bitlong4669]

Very cool project. Thanks for detail explanation. I shall start assembling the required parts and follow you footsteps. For testing… could you not use some kind of electro-photo device, like a phototransistor?

[@RockyPondProductions]

You need cooling. It is essential that the cavity is cooled on a YAG laser. Seal and encapsulate the the cavity in a cooling chamber with good water flow and that will help with the performance and overall reliability.

[@flaplaya]

Pretty sure voltage is proportional to output wavelength. Good luck getting it working.

[@TheClumsyFairy]

Please Please Please do part 2..

[@deepnitrox]

Any news?

[@nekotherion7317]

Would throw a resistor before the caps, might trick the PSU you have, into thinkin its a 'stable' load

[@frankcarter8399]

Great video... I bet we are all waiting

[@Daedronus]

Electrolitics can't discharge fast, with just the wire inductance you are prob in ms range for the discharge

[@Daedronus]

But that will not be a problem, yags(or nd glass) really want to lase, your cavity is probably more of a problem then the caps, that rod will lase even with 10uF @ 700v

[@christopherleveck6835]

Is it a problem having a "seem" down the length of the housing? I could bore a hole through a solid piece of aluminum with an uninterrupted mirror finish. It would come off the machine that way. So no further polishing would be needed.....I would guess that additional polishing would introduce a "wavy" surface finish whereas straight off the lathe it would be all perpendicular and concentric faces....if the light is meant to bounce around in there in an orderly fashion?

[@ashleyobrien4937]

just wondering, would it not be a good idea to have the length of the rod polished ? I'm just guessing but it looks to me like the surfaces are quite rough/opaque compared to the highly polished ends of the rod, would that not help the pump light to enter the rod more efficiently with less scattering ?

[@BothoHohbaum]

looks as if you have so called high pressure xenon lamps. i have an old tattoo removal laser (passively Q-switched Nd YAG) here, it uses a low pressure xenon flash lamp. the lamp has max half the thickness of your lamps, is shorter and runs at up to 700V-800V. afaik, those have much higher explosion energies. when i short the capacitor to discharge it (through the lamp inductor to minimize stresses) it still sounds like a shot from a pistol. it's loud enough to make my ears beep when fully charged. the same discharge going through the lamp makes almost no sound, just a whispering "click". additionally, high pressure xenon lamps have the biggest peak in their spectrum at 1064nm, exactly the same wavelength as the laser output, which maximizes conversion and minimizes heating. i don't know, if the spectrum of low pressure xenon lamps is equally optimal. my general quess is: you have still not enough photons for a population inversion. when i drive mine at lower energies, it becomes a normal flash lamp, no lasing. you should be able to recognize the laser output in case it starts to lase with that setup. no high tech required. just something in front of the laser like a newspaper. when it lases, it starts to explode the ink off the paper. you'll hear it and see plasma balls exploding from the surface of the paper. well, at least that is how my laser behaves, it has this passive Q-switch added. your results should differ more or less. possibly your laser starts to lase at lower energies without this passive Q-switch.

[@thatoneguy99100]

I think you will have a hard time with two planar mirrors. You might consider swapping one of them for a spherical mirror, which should make alignment easier.

[@EricThornton24]

While I did eventually get this working with the plane parallel mirrors (check out pt. 2 😉 ), you are right. It was very difficult to align and very difficult to keep aligned once it was. A more forgiving cavity would have made things easier - next time!

[@unitedspacepirates9075]

Microwave excited sulfur plasma lamp works great for pumping yag lasers.

[@shawnio]

after you're done you're like, ok now what the hell do I do lol

[@shawnio]

look at the size of those capacitors lol wow

[@icebluscorpion]

You need to have standing waves in your rod to achieve amplification AkA your rood must have a specific length of a multiple of your emissions wave length other wise it will not work with the pumping and remission cycles. Also why do you put them in a circular mirror you need a eclipse mirror to have two focus points.

[@rocksnot952]

Wouldn't it be less lossy if you pumped the laser rod with appropriate laser diodes? No high voltage power supply, less cooling, etc...

[@Alexander_Sannikov]

very sad you didn't do a follow up. I think your fault has to be the alignment : when I was aligning a HeNe laser back in uni lab, I do remember seeing an interference pattern. I used a red laser keyring pointer to align it. another thing that makes me very suspicious is your 80% mirror: in order to lase your resonator cavity will have to have at least 20% gain per period which's ridiculous, at least for HeNe laser that i was working with. and lastly, are you sure that the rod's alignment does not matter? i aligned our laser with the working body installed.

[@nicktohzyu]

18:00 for the cavity, why not go with gold/copper plating?

[@sgajate]

Nickt's got a point here , you know? I've worked in a laser research institute and have seen a couple of elliptical laser cavities, all of them, gold plated. That really makes a huge difference! Anyway, great work!!

[@astinazarafza8360]

how about using silver mirror reaction for coting the inside of the chamber in silver

[@0x90meansnop8]

Thanks for the bible. Good Job!

[@Alexander_Sannikov]

this old tony, is that you? why did you write a script for this guy?

[@dimetriosprice2094]

Is there any way to make the tubes from scratch?

[@mrdontplay6256]

Should sputter coat the concaves of the aluminum rod housing with gold. You’ll get much better energy transfers from the flash lamp to rod. It’s not that expensive.

[@tombouie]

Wait a minute, I didn't really see any solid-state circuitry inside his laser ?did-you?

[@eragonawesome]

What's with the weird interlacing here? Was this filmed on an actual film camera or did it just have the auto de-interlace feature enabled on whatever editing software you use? Other than that, great video!

[@rickt1866]

electroplating gold on the ellipse or another highly reflective material? anyways thanks for the upload enjoyed the detailed information.

[@skachati]

Nice work. Put some camera to film what is going there inside)

[@blackIce504]

you could try electro plating your chamber.

[@jannejohansson3383]

You "must" use spring, spiral tube or catch real flash from thunder storm to glass jar.

[@merittmarks9525]

Could you use a copper or gold sleeve that would get pressed into the hole?

[@Mister_G]

Fascinating! And very well produced - congratulations. :) I can't help think that your mirror mounting (the aluminium flat plate) is nowhere near stable enough (mechanical & thermal effects will affect it greatly), I have never built a LASER, but I did have to align one years ago, and even with silica / invar rods to space the mirrors at all 4 corners, it was *extremely^ twitchy - you don't start seeing the interference patterns until it is very, very close. Subbed, and looking forward to pt. 2.

[@MrBleulauneable]

I'd disagree with calling his setup not stable enough, thermal effects might become an issue when running continuously the laser because you do pump a fair amount of power in that piece of metal in the end (a 600J pulse will heat a 1kg piece of aluminium about half a degree) but aligning the empty cavity shouldn't be an issue. With a planar cavity like this the alignement is the same as aligning a Michelson interferometer which should be fairly easy given the very appropriate hardware he has (although the procedure used may be inapropriate). In my university aligning a Michelson interferometer with a HeNe was thaught in about four hours to a first year uni student with no prior optics experience on a setup with the same mirror mounts he has bolted to a piece of metal.

[@Mister_G]

​@@MrBleulauneable Just temperature variations in the room will cause thermal gradients in the aluminium slab that the mirrors are fixed to sufficient to cause the mirrors to go out of alignment (unless he is working in a constant temperature room). There does not seem to be any consideration of the mechanical support for the cavity (there may be but it isn't obvious) - the weight of the device just seems to rest at random points on the mirror support bar. If these change, the alignment of the mirrors will change. I have looked at a lot of optical layouts created by physicists, and (in general) they have been appallingly constructed. I have also made / aligned / used interferometers routinely, but still found aligning a laser cavity extremely difficult (to the extent that I thought it was impossible at one point, and this was with a commercial laser with very good mechanical design). I think the mirror mounts are OK, it's just everything else! :)

[@MrBleulauneable]

@@Mister_G Can I ask what cavities you're talking about that you found hard to align ? Because I totaly agree that they can get really difficult to align on some fancy laser, I've had to align the cavitiy on some femtosecond Ti:Sa lasers and it was quite challenging. But that's not really what we're talking about here, here it's pretty much the simplest cavity that can exist (maybe not the most stable one but still). And I don't think temperature changes in the room will be an issue on the timescale of the alignement, at worst it might be an issue from one day to the other but again for this application it's probably irrelevant. And if you compare this 30-ish cm slab the 2*3 meter steel optical tables you typically find in optical labs that sometimes aren't even temperature controlled, you can understand that thermal expansion isn't always a big issue. And you can look up Michelson interferometers that are sold for student training and they're essentially just two mirror mounted on a 1cm thick slab of metal just like this laser (this one for example : www.didalab-didactique.fr/site/materiel/EN-categorie-36-produit-793.html), and they work just fine.

[@Mister_G]

@@MrBleulauneable Argon ion, I believe - about 1.2m long. (it was ~30 years ago). On the other stuff, we will have to agree to differ. :)

[@Dwarfracer88]

MisterG, would the index card being, I'm guessing, .250" away from the focal lens of the source laser and also not square to the setup have an affect on seeing the interference pattern?

[@danwalsh5282]

Do you think the soviet flashlamp would have worked in hind sight?

[@danwalsh5282]

*hindsight

[@TheRainHarvester]

LOL I skipped ahead right before you did the ff effect...then I went back.

[@CharlesVanNoland]

"Farm-achey-uhhh" lol. I would've assumed something like "Farm-ay-see-uhh", "Farm-uh-keeuh", or "Farm-ace-shee-uhh"

[@sergeynalimov68]

What problem make a diffusion reflector from white porcelain or ceramic?

[@MBouchard]

You clearly have skills so why don't modify the internal stuff and blow your own tube for it?

[@TheRainHarvester]

Only 10^4 flashes?! That wouldn't last very long. Cw?

[@swamppifi6186]

at 20.36 there is a quick flash of a message screen. slow your playback speed to .25 speed so you can read it...

[@tombouie]

Well-Done & Quite-Fun

[@alllove1754]

Cloudray sold me some, gold tinted for infrared

[@johndoggett808]

17:40 "I planned to get it machined". What sort of service did you use? I was expecting you to do your own machining, possibly at a FabLab. I suppose a job shop of some sort is sensible. How did you find the service, and is it expensive? Great video!

[@EricThornton24]

Hey John, I used a service called 3D hubs to get the parts machined. The reason I didn't go into detail in the video is you need a "non gmail" email to use the service (I was able to use my .edu address) so it's not really an option for everyone who wants to get into lasers. It is also very expensive, especially for one offs. As I continue this project I am going to utilize community machining options (maker spaces, etc) for any machining that needs to be done. Thanks for watching, -Eric

[@hubbsllc]

1) I really feel like you've got to make the mirror alignment with the rod in place. If the rod end surfaces were perfectly parallel there would be no difference between in place and not in place, but I think you've established that rod end parallelism is not a given. Your optical cavity may be bounded by the mirrors but ultimately the cavity includes the rod. The ends of the rods aren't really giving you the amplification anyway. 2) If aluminum surfaces have an absorption dip right where it hurts you the most, you wouldn't have to make the reflector out of copper or gold - you could make it out of aluminum like you did but gold or copper plate it instead. Copper would corrode but the gold sure wouldn't. 3) Amateur astronomers do silver their own mirrors, I believe - I think with vapor deposition. how would it be to vap-dep one end with some metal or another? Please let us know how your project progresses!

[@guvyygvuhh298]

This is some quality shit, how can you only have 122 subs?

[@nicktohzyu]

20:35 isn't a rotation about an edge point equivalent to a rotation around the center plus a translation? and translation of parallel mirrors shouldn't matter?

[@TheRainHarvester]

Yeah what gives!

[@nicktohzyu]

@@TheRainHarvester iirc this contradicts with what was said in the video at the timestamp

[@ahmetmutlu348]

Alsotheorically if reflected light cant find way out, itll explode too.. i mean just pushin energy inside it becomes critically high. I mean lasers has keys for cheap nuclear weapos too . but probabl there is no good eneugh reflectrs to do it for now.

[@1st_ProCactus]

If you make them small enough, you can put one on each arm :D

[@DmitryKiktenko]

25:20 - tube exploded because it was soviet. Sometimes you could see soviet stuff inherited thru the generations and still works well. But these samples are all family relics, and you can't find them on ebay. This is partially a joke. )

[@danieolivo2438]

Is it Nd Glass? Isn't that YAG or YAP? Flashtube is IFP-800 or INP3-7/80A? Made in USSR? :) Laser rod also made in USSR? :)

[@texasslingleadsomtingwong8751]

Time to sputter a gold coating on the reflective chamber.

[@joaopaulodesouzapinto9453]

Qual o nome do software Cad usado?

[@joaopaulodesouzapinto9453]

what is the CAD software used?

[@EricThornton24]

Fusion 360. It's great, and free for hobbyists!

[@ajingolk7716]

INP3-7/80 equivalent lumens?

[@PvPbomber009]

Very cool video, keep it up! :)