ฝัง
- เผยแพร่เมื่อ 26 มิ.ย. 2024
- Episode 55
#optics
#laser
#nonlinearoptics
#photonics
In this episode, let’s look at growing non-linear crystals that can convert Laser Light into different colours, using a process called second harmonic generation. The crystals we will be looking at are the same crystals used in the National Ignition Facility, a Laser driven Nuclear Fusion experiment!
Here is a superb paper on the National Ignition facility (takes time to load!):
www.osti.gov/pages/servlets/p...
/ @livermorelab
1064 laser module： bit.ly/3ZTLKeZ
Check out my other videos: / leslaboratory
Please don't forget to like, subscribe and comment for more great content!
If you found this content useful, and would like to support this Channel, please consider supporting this work on Patreon: / leslaboratory
Or donate directly: paypal.me/leslaboratory
Alternatively, please share this content on your social media platforms, it really helps the channel!
In this episode, let’s look at growing non-linear crystals that can convert Laser Light into different colours, using a process called second harmonic generation. The crystals we will be looking at are the same crystals used in the National Ignition Facility, a Laser driven Nuclear Fusion experiment!
Although non-linear crystals can be prohibitively expensive to manufacture, considerable research has been conducted into growing them at large scale and inexpensively, especially for large systems. One such system, is the national ignition facility. This is a laser-based inertial confinement fusion research device, located at Lawrence Livermore National Laboratory in the United States. It is the largest and most complex Laser system in existence, with over 7,500 meter-sized optics, and 26,000 smaller ones. The facility itself takes up the space of 3 football fields and can deliver up to 2 Million Joules of ultraviolet light and 500 terawatts of peak power into a fusion target the size of a pencil eraser called a Hohlraum. This generates the extreme pressures and temperatures necessary to achieve nuclear fusion. It achieved the first instance of scientific breakeven controlled fusion in an experiment on December 5, 2022, with an energy gain factor of 1.5 (Note, this does not factor in actual power consumption of the facility, an important omission by
the popular press! Nonetheless a huge achievement!
1064 laser module： bit.ly/3ZTLKeZ
Check out my other videos: / leslaboratory
Please don't forget to like, subscribe and comment for more great content!
If you found this content useful, and would like to support this Channel, please consider supporting this work on Patreon: / leslaboratory
Or donate directly: paypal.me/leslaboratory
Alternatively, please share this content on your social media platforms, it really helps the channel!
0:00 Intro
0:18 Second Harmonic Generation
0:43 Discovery of SHG
1:17 Expensive Exotic Materials
1:37 Research and the National Ignition facility
3:15 Potassium Di-Hydrogen Phosphate (KDP)
4:03 Growing KDP at home!
6:07 YAG Laser setup
6:57 Generating Green light from Infrared
8:21 Thanks to channel Supporters. - วิทยาศาสตร์และเทคโนโลยี
You are covering topics that I haven't seen covered on TH-cam before. And your explanations are extremely easy to understand for someone without any background. Keep up the good work! I get very excited whenever you post a new video.
Thanks, I am really glad you like this stuff!
I don't know why, I just always assumed the crystal needed to be cut and facetted to work! I started growing crystals with the aim of eventually making a working KTP crystal, which got me into chemistry. Very cool video. You always have unique content, bringing the cutting edge into the realm of the hobbyist.
You would be surprised at what works! I have a failed KDP crystal that is milky in appearance, and the whole thing glows green. I have already tried a quick test at cutting and polishing a reasonable crystal and the results are very promising!
@@LesLaboratory I have a sizeable CE:YAG crystal in rough cut, im trying to find a cost efficient way of cutting it into as many test pieces as i can. im looking to make 10x10x1 mm slices, some smaller, some bigger for experimentation. Have you made much progress or have any tips for this?
This is what I dreamt of as a child obsessed with lasers. Very cool and also thanks for mentioning some cool papers to take a look at
Me too! Speaking of papers, here is an excellent one on the National Ignition Facility (I have just added it to the description): www.osti.gov/pages/servlets/purl/1256427 It takes time to load, but is very worth it!
DIDO!
@@LesLaboratoryYou freaking rock man!
I would draw laser tubes rather than do my math work lol
Superb video. Without any question, the finest, most beautiful, and clearest exposition of the phenomenon to date anywhere on the internet (and I've seen pretty much all of them!).
Though obviously not necessary for the home experimenter, on the "real thing" for a fusion laser we couple each crystal in its gimbal to a thermistor, such that the temperature sensitive nonlinear coefficient of the crystal may be compensated for due to slight fluctuations in ambient conditions of the laser bay. The crystal doublet in the gimbal is electromechanically actuated, such that each crystal may be "tuned" or detuned to produce 1st, 2nd, or 3rd harmonic light as desired. Further still, we demand the supplier of crystals (and there is only one on the planet capable of growing them this large - Cleveland Crystals) makes the KDP not out of potassium dihydrogen phosphate, but rather potassium diDEUTERIUM phosphate (KD*P) so that the tiny residual infrared absorption at 1053nm due to one of the overtones of the hydroxyl group stretching vibrational modes in the crystal is red-shifted further into the IR (the deuterium is heavier and so the molecule vibrates slower), the crystal thus becomes more transparent at the fundamental line and more efficient at converting to higher harmonics.
It always struck me as weirdly ironic that in order to do inertial confinement fusion you need deuterium in the target capsule AND deuterium IN THE LASER too!
Thanks! :-D
This is a really nice description! Even for home use, a proper gimbal is probably a good idea and I am thinking about it.The rotary stage gives me only one axis of rotation, and the half wave plate does the functional equivalent of rotation about the beam axis, but this is still far from properly tuned.
Funny you should mention KD*P, someone else asked about that in the comments, and I pointed them to this: www.nature.com/articles/s41377-022-00929-y but your explanation provides the why to the papers' what, thanks!
I had exactly the same thought about the Deuterium thing. I was having a cursory read about the precursors to all this (Shiva, Argus, Novette etc) , absolutely beautiful stuff. I am sure there is something interesting buried in some papers somewhere!
Hi Les very nice video I have used my ANOVA Sous Vide wand to keep the water bath at a constant temperature to grow the KDP crystal and it has turned out to make large clear crystals perfect for SHG laser light
Great tip, I will be trying seomthing similar. I was thinking of wraping the beaker in that flexible heating strip you can get for vivariums.
@@LesLaboratory Watching this I started thinking about temperature regulation ideas too. I think something like the sous vide or using a heating strip or immersion heater in a larger volume of water which the beaker then sits in might be a better approach than directly heating the beaker itself.
Putting heating strip directly on the beaker with the saturated solution will probably result in convection around the edges & uneven temperatures, as well as the need for a temperature sensor to be immersed in the crystal growing solution.
Sitting the beaker in a large volume of temperature controlled water will eliminate those issues, and will have a lot of thermal mass to minimize temperature fluctuations, even when a cheap thermostat (non PWM) type temperature controller is used (eg an aquarium heater). You could even use a cheap 12v water pump to circulate the water bath to ensure absolutely uniform temperatures while still keeping the crystal growing solution undisturbed.
FWIW if you're thinking of building an Arduino/rPi/ESP32 temperature controller, I've had good results using the DS18B20 temperature sensors - low cost, precise, plenty of open source libraries/drivers available, and they work on 5V or 3.3v micros. It might also be worth mentioning that vape shops are also a good source of very cheap SS316, Kanthal and Nichrome resistance wire suitable for immersion heaters too :)
Your channel is a great resource for me! I am determined to study laser engineering and optics in a few months. Your videos no doubt helped inspire me to chose this field.
Thanks Les
Thanks! That's so great to hear!
Awesome video, I just came across your channel! I interned over at NIF over the summer and had the pleasure of working on some other photonics applications within their photon science division. Though, currently I'm PhD student working with fiber frequency combs for time-transfer technology over at NIST. I was going to suggest showing supercontinuum generation, but looking more into your videos it appears you already did that. Keep on the killer work!
Thanks! Wow, interning at NIF, spectacular! I would love to see inside there some day! Of all the videos on my channel, I always thought Supercontinuum would be the one that took off. By far the coolest piece of work I have done. Cheers!
Great to see that you had sucess in using homegrown crystals for SHG!
A pockels cell would open up quite a few interesting applications, from q switching your own laser to a regenerative amplifier.
For Sure! I have had some luck cutting and polishing a crystal, but there is quite a bit of work to refine the process, but the results are pretty promising.
@@LesLaboratory Glad to hear you had some sucesses!
5:00 Rochelle crystal is used as seed crystal for perfect Crystal Atomic orientation.
I love seeing people pushing the limits of hobbies and home labs. Great job! Keep pushing!
Thanks!
Amazing Production Quality Les
Thanks! Been taking advice of a few commenters, and it is getting there :-)
@@LesLaboratory😊 - still thinking about something to make the intro better, yet still easy for you to record. Are you sitting down there?
Very nice! Can't wait for more!
That's freaking amazing! I can't believe how successful that was. Thank you for demonstrating this. I'll be sure to donate to Patreon as soon as I can.
Thanks! I am glad people like this stuff as much as I do!
Amazing! Really enjoyed this demonstration. Thank you!
hah! I literally said out loud "WOOOW!" when you got that pretty green beam out of the crystal. Pretty impressive Les :)
Thanks! it is very cool!
Outstanding work as usual.
Thanks!
Accurate reporting, thank you
Super, thanks.
Thank you sir.
This is excellent.
Absolutely top notch 👍
Thanks!
So that's how my green laser pointer works - nice!
Thanks!
Outstanding thank you. Great inspiration for others.
Thanks! :-)
Sweet! The crystal video is finally out! 🍿🍿🍿
Thanks! I think there is more to be done here as well!
Very interesting,owesome content as always!
Thanks!
I wanted to grow a KDP crystal a couple of years ago but work and messing around with my Ruby laser power supply and my FAP 40W laser took over. This is a great video full of useful info that I didn't know so thanks for that and I can't wait for the next few videos at minimum! Great work Les!!
Thanks! The beauty of crystal growing though, is they can be sat on the shelf, being ignored whilst other projects are happening ;-)
Brilliant
Beautiful!
Thank you!
This is awesome! Subscribed. 👍
Oops, I already subscribed!
Awesome!
Thanks!
Amazing!
Thanks!
Great experiment
Thank you 🤗
Awesome! Congratulations on your success.
Thanks so much!
Really cool ^^
As you always say: ABSOLUTELY FANTASTIC!!! Look forward to further videos. You're the best!!!
Thanks! I am glad you like this stuff!
@@LesLaboratory I’m building N2 Laser following EXACLTY your design (charge transfer). If it will work I’ll show it at the next Maker Faire in Trieste (Italy) next September. Of course I’ll give credits to you!
@@LesLaboratory Dear Les, I succeeded!!! The N2 laser (based on your tutorial) is working perfectly! And I’m also able to excite rhodamin6G emitting on super-radiance!!! I’m so happy!!! Thanks for your fantastic tutorials and design suggestions!!! 🤗🤗🤗 if you give me your email address I’ll send you pictures. Thanks and best regards, Massimo Cappello from Italy.
I had a neighbor that worked at Brookhaven. My neighbor grew crystals in his lab that he then used an electron beam to map the molecular make up. The results were used to develope electrical conductivity and resonance response. This was in the mid 70's.
Nice!
Interesting, I can't wait to see the rest of your work. Plasmas are the ultimate mad scientist toy. ❤
Wow! Thought the angles have to be matched much more precisely to get any second harmonics.
At low powers, say in a Frequency doubled DPSS, the angles are very critical, however the higher the power the more efficient the doubling becomes so small deviations in alignment become more tolerable.
Laser optical traps have achieved matter condensates as Keitaro Yoshihara and Casparian have even produced Nimbus storm clouds since NdYAG tunable could function as a laundromat able to fit into luggage.
Looked like there was some third harmonic light in the seed crystal emissions. Cool!
I have tried for THG, but no measurable success yet, it might just be IR messing with the camera. For THG crystal orientation and polarizations of the beams is...tricky!
well done.
Spectacular! Thanks for your support!
I doubled the kdp to 100g and used 400mL of water. Heated it in a beaker and stirred until all kdp was dissolved. Next, I poured it into a wider dish and then put the dish into a styrofoam cooler. I cut out 2 holes in the top of the cooler and covered them with filters so that the evaporated water can escape the cooler. I kept my apartment at 70-72 degrees F. Clearer crystals were grown once I kept it at a constant temp of 70 degrees F. After about a week, I have 2 big cloudy crystals, 1 medium sized super clear crystal, and 1 tiny clear crystal. These are just the seeds. I’m going to wait a day or two longer before I put the super clear crystal into a new container and suspend it.
Fantastic! Yes, I have noticed with KDP that it can be a bit of a hit or a miss, especially if there are any temperature variations. I have been spending the last couple of months growing KDP using various methods. The largest I have grown is over an ounce, but is only clear in one or two sections, but the results so far are pretty promising. Let me know how you get on with it.
Amazing it s the word
That's literally the coolest thing ever that a giant laser is coming out of just a solid regular see-through crystal, It looks so crazy and dope and sci-fi, amazing and beautiful video thank you
Thanks!
Excellent video. I think it was really cool to demonstrate crystal growth and phase matching properties of nonlinear crystals! In addition to the 'yaw' angle adjustment, you might get a small improvement by adding a pitch adjustment as well, since the crystal may not lay perfectly flat on the platform.
Have you ever witnessed the 'rings' or additional features that arise noncolinear effects rising from k-vector addition on the crystalline lattice?
Also, you you use your SHG beam and send to a second crystal for DOPA, to get quantum entangled photons!
Perhaps placing the crystallization beakers in a cheap polystyrene cooler would help level out the temperature swings.
I am now using Mylar Bubble Wrap, we shall see how it goes.
I would love to see a scintillator crystal be used in second harmonic resonance and convert uv light to pure yellow or white
Amazing work Les! I'll have to get some KDP now I guess 😁
Thanks! It is cool stuff, and pretty cheap!
Nice video. I get to play at NIF, and it is something else to be able to walk around inside a laser. :)
That sounds amazing!
Neat experiment, I would like to try that (sure, directly doubling the VCSEL wavelength won't be doable, but I would try with KDP and see what happens).
+1 to rotary crystallizer future video. Especially if its one that can be 3d printed.
I am already acquiring parts! I don't own a 3d printer, but I have Laser cut the stage and motor mount out of acrylic already. Perhaps the files can be converted...
I still need to get other parts yet, notably a heater, and a source of reagent grade KDP, but it is coming along!
Beautiful demo! I’d love to try growing crystals and see how they behave. I have a 60W fiber laser engraver, and if you set it to just scan over a small pile of crystals, you get loads of green flashes. Being focused, it’s very easy to get the intensity.
You should. There are a whole bunch of crystals that can be grown that will do SHG.
@@LesLaboratory I found that aluminium nitride does it very slightly (th-cam.com/video/WdZHd7YGEys/w-d-xo.html) when I was messing around with the stuff. Amazingly, if you laser engrave it, the surface transforms into a thin aluminium layer!
@@imajeenyus42 now that is interesting. Is the aluminium layer contiguous?
@@LesLaboratory Yup, it seems to be - it's not exactly smooth and shiny, because of the roughness of the lasered surface, but it's definitely conductive. When I was playing around with it, I could get tracks down to a few ohms resistance. Quick video here as well - th-cam.com/video/QQiGjbQBlv8/w-d-xo.html. The deal seems to be that AlN decomposes above 1800°C or so into aluminium and nitrogen. The layer isn't very thick though - one paper I found talked about 1um or less.
@@imajeenyus42 nice! I wonder if it would take electroless plating. I must get a fiber laser!
Fantastic, Lasers and a bit of Chemistry too ! does it get any better ?...cheers RIP Calculon
Very impressive!
As you may have already discovered there is crystal cutting and polishing gear available for hobby lapidary work. Lapidary clubs could be helpful also.
I guess the crystal can be cleaved using a sharp point.
Thank you for such interesting content!
Thanks! Yep, that and optical polishing were my first ports of call. KDP is quite soft, and can easily be rough cut and ground, and even get a reasonable polish in just a few minutes. I have already tried this with a failed crystal as a test. I just need to grow large clear enough crystals.
very nice, i hope one day the reverse way will be possible : take 455nm laser to go 910nm laser beam. I want it to cut some material with cheap 450nm laser diode
Thank you for such a great video. Keep it up !
I'm just wondering. Do you think making it periodically poled is too challenging to be done at home?
Well, that depends on determination and budget I guess! I have not heard of it being done with KDP, but it can be done with KTP and Lithium Niobate. From what I understand there are a few approaches though most require exotic equipment! Probably, in an old journal article somewhere, lies an odd but achievable way of doing it.
@@LesLaboratory yeah. My question was too vague, yet you gave me a nice answer. Thanks :) you are right, its the budget in the end
💛
Great job growing your own crystal and then using it in your setup! That's a great achievement!
I wonder how quickly the crystal faces will degrade with the moisture in the air, as crystals typically purchased are AR coated to also protect from humidity. I also wonder how the damage threshold of your crystal stacks up to commercial ones.
In my lab I'm always very happy when the peak power of my pulses is naturally in the MW regime, so I don't need to set up focusing to achieve efficient SHG.
Thanks! These crystals have been out for a few days now with no visible signs of degradation. If they are kept dry (and I don't breathe on them!) I think they will be good for a while. They are hygroscopic, but not deliquescent. I suppose I could build little sealed chambers for them on the lathe if it become a problem.
Yeah, with huge peak powers, you can more or less chuck a crystal in front of the laser and you are done. I have a nice YAG under the bench that barely cares at all about the orinentation of KTP!
@@LesLaboratory awesome! I know. With enough oompf even Pockels Cells start to convert the fundamental.
What an interesting effect. Is there a similar effect, but in the opposite direction - with a decrease in the output frequency? In the X-ray range, for example. It would be possible to create an X-ray telescope based on this effect with high resolution. I know that it is very difficult to focus the light of the X-ray range, if its frequency were lowered to ultraviolet, then the task of focusing would be solved much easier.
How did you prevent dendritic/feathery crystals from growing up the side of your glass jar from the meniscus as it evaporated?
Brilliant!
Eagerly awaiting cutting & polishing video 🙂
It's coming. I have an intersting polishing method, I am just working on growing Large crystals.
Hi, thank you for excellent video. It would be nice if you can make video about building that 1064nm laser module with off the shelf components (Thorlabs etc.). What would be needed and its alignment, and same with collimating optics. -Jarno
Thanks! I got this module from Twotrees Engraving company: 1064 laser module： bit.ly/3ZTLKeZ I suppose one could be built using parts from Thorlabs, but I have not seen any Nd:YAG or Cr:YAG on their site...
This is AMAZING!!!
Question, can the crystals be used as a scintillator for cameras? Meaning if I was able to get a crystal that converts, UVA UVB light into some other color that the camera can detect.
Thanks! Unfortunately no. These crystal require an extremely high light intensity in order for the nonlinear effect to become measurable, something that ordinary light sources can't do. It is possible to image in the UVA and UVB though with black and white camera sensors with quartz optics.
Awesome stuff Les! I've wondered whether it would be possible to pull this off at home for some time now. Do you think it would be just as easy to get 404 nm violet light using an 808 nm diode from a laser printer?
Thanks! Non-linear effects typically require extremely large power densities or high peak powers. The Laser in this video is pulsed and gives peak powers of greater than 15kW so doubling is very straightforwards. It is not likely that an 808nm Laser diode, would give visible output using KDP. That said there are directly doubled Laser diodes out there, but the crystals for those are exotic and the tolerances super tight.
so could you "stack" these so that the beam coming out of the crystal goes into another and further harmonizes the beam?
what would happen if you focused a blue laser through one of these crystals? or really any other?
❤
You will get a lot more green if you focus the beam inside the crystal. Use a lens with about a 5 inch FL. Also heating the crystal a bit helps it operate more efficiently .
Yep, I was afraid of hitting any flaws or imperfections though. I might try ovenizing them, it could make for an interesting experiment!
This is great stuff. I'm wondering if a DIY lab can move up in frequency/energy and do some simple(?) X-ray crystallography.
Seems unlikely.. The only coherent X-Ray source for any purpose that i'm aware of is the free electron laser, and that needs a synchrotron. If such a thing were easy I doubt the semiconductor industry would be pouring billions into developing 65 nm EUV light sources.
Back in the day I used to build x-ray machines (I posted tons of stuff on 4hv.org), however I need to get a workshop outside to get back into that kind of stuff. But sure, with a small collimated x-ray tube and some math, x-ray diffraction could be done. you can even buy machines like the Tel-X-Ometer for this, but they are pricey!
Here is an interesting presentation of table-top coherent x-rays: th-cam.com/video/53cCTcGWCeo/w-d-xo.html
Very cool. I'm honestly impressed by the results with just raw crystals. Why is the National Ignition Facility using deuterated crystals, though?
Thanks! Deuterated DKDP has a higher threshold when Tripling into the UV: www.nature.com/articles/s41377-022-00929-y
@@LesLaboratory Huh, that's super interesting. Can't wait for the next video.
I always assumed that the ends of cut and polished crystal had to be coated with AR and transmissive films to get the second harmonic?
Well, it would certainly help. At low powers absolutely, but when you are hitting it with Kilowatts of peak power you can get away with it.
You could use a cheap incubator to stabilize the temperature, so maybe try that?
Yes, I was thinking of getting hold of the flexible heat mats that you can get for vivariums, wrapping it round the beaker and building a temperature controller. This is kind of how they do it at the NIF. They run the baths at 40 odd degrees C and slowly cool over the course of a couple of months.
@@LesLaboratory Or grow them in a thermus flask.
I wonder how you managed to get the second harmonic at such an angle (phi equal to 0 or 90)? I was able to get generation only with theta angles around 50 and phi 45 respectively. What type of generation is happening?
EDIT: According to the referenced paper, Type I, but this is not in agreement with other papers which quote Type II ! There may be an error here that warrants further investigation, but bear in mind this crystal is un-cut, and the surfaces are far from flat, so anything is possible.
Can these crystals be used in night vision? For example if i put the frequency doubling crystals on some glasses to see infrared
Unfortunately not. This effect only occurs at extremely high light intensities. In the video the Laser uses produces a series of pulses at about 15 kilowatts each.
Where do you shop for those table tools?
The breadboard came from thorlabs. All the mounting hardware came from aliexpress. Anything special I make myself on the lathe.
@@LesLaboratory Thanks I'll look them up. Shit's not cheap is it. Wish there was an affordable version. Don't need lab quality to play with ideas.
Will these work for pumped phase conjugation ? Barium titanate is very expensive
I don't think so. From what I have read, phase conjucate optics are used to correct wavefronts that have travelled though KDP, as KDP distorts them. Phase conjucation would be an interesting topic to explore however.
@@LesLaboratory do you think you can try your hand on a video of using KDP crystals that are polished for pumped phase conjugation ? Or growing barium titanate BaTiO3 patent WO2001006042A1 talks about growing singular barium titanate crystals for use I would love to see a video on either or if you can
If you put two crystals in a row, does it frequency double twice (resulting in ~350nm at 1/4 total power)?
Or does the resulting green beam pass straight through the second crystal, unaltered?
I'm curious how two in-line frequency doublers differ from a triple harmonic crystal, if any.
Disclaimer: I do not understand the phsycial principles/mechanisms lol
Sort of. Depending on the cut you can get the third harmonic at 355nm from a second crystal. This requires special cutting, polishing and alignment. It is also possible to get the fourth harmonic at 266nm, but this requires precision temperature control to work, and high peak powers.
heat up some vivianite with laser please
Me in 1998 getting my first argon ion laser: "Blue lasers are WAY cooler than HeNe or IR! I wonder what other colors are out there". *Looking on Don Klipstein's site*.. "A pity dye lasers are way out of reach for hobbyists!"
Les's lab 2022: Makes several different colored dye lasers with eBay parts
Me in 2006: "Wow! Blue diode lasers. We can finally make solid state white lasers! Pity they're really only 3 wavelengths mixed together and a true white laser would be impossible"
Les's lab 2023: Makes supercontinuum laser..
Me in 2010: "Wow! Pump laser diodes are getting cheap" *Looking at KTP prices online.*. "A pity that big SHG crystals are way out of reach for hobbyists!"
Les's lab 2023: Grows massive SHG crystal from plant fertilizer...
You have my vote for the best laser-centric TH-cam channel by far!
Wow! Thanks for the nice comment!
It's a pity the channel wasn't about in 2007, I would have gotten a billion views with the Blu-Ray laser project, at the time, it crippled my site, and laserfaq got a hammering as well!
I want the crystal that outputs double the power put into it.
..and then feed it back into itself and watch it explode. :-) But in all seriousness, you can increase peak power (think Q-Switching), just not average power!
What about danburite
Growing it? Or SHG with it?
I would love to see you make a pockels cell! I would also love to see you make an ITO [Indium Tin Oxide] optical switch as used in this experiment: th-cam.com/video/NsVcVW9GI60/w-d-xo.html
It will be interesting figuring it out! This video is very cool! I will look into it, and see if anything practical can be done with it!
It's already an interesting video, you really don't need the irrelevent clickbait title
Thanks! I'm trying to poke at the algorithm to push the content. Too many people have commented that they only find this channel by accident.
Suggestions welcome!
Doesn't this effect violate the 2nd law of thermodynamics? I find it hard to believe it does. But could someone explain why not?
Two photons of low energy (1064nm) are "combined" to one photon of twice the energy (532nm), Therefore the total energy out is the same as the energy in. In a real system, you also have losses as well.
Weird, I though you needed optical cavities to get self sustaining second harmonic effects?
Once you get into high peak powers, a cavity is no longer needed. The laser shown produces peak powers of 15kW and so the power density is large enough to demonstrate the effect. This is not particularly efficient at this power level, but at higher powers, efficiency really starts to take off.
Nuclear fusion NOT INCLUDED
...yet.
牛逼
谢谢
This is some arcane magic bs 😂
0:46 When is Et Al going to get his Nobel? Seems he has contributed to most scientific papers;-)