Growing Laser Crystals used in NUCLEAR FUSION!

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!):

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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!

Please don't forget to like, subscribe and comment for more great content!

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.

[BestSpatula]

You are covering topics that I haven't seen covered on YouTube 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.

[yasurikressh]

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

[braddofner]

I love seeing people pushing the limits of hobbies and home labs. Great job! Keep pushing!

[omsingharjit]

5:00 Rochelle crystal is used as seed crystal for perfect Crystal Atomic orientation.

[WaffleStaffel]

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.

[okooptics]

Incredible work and video. I just set up an off-the-shelf BBO crystal in the lab for second harmonic generation. I would never have imagined growing a nonlinear crystal at home! And the result looks very impressive.

[Muonium]

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!

[Shonade_Malik]

HELL YEAH! You can barely find any videos on YouTube on how to grow these kinds of crystals, so thanks a lot for this!

[stevehill]

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

[TheTablet]

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.

[stevengill]

So that's how my green laser pointer works - nice!

[alexbarnett]

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.

[danriches]

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!!

[davidedgar]

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.

[theaeecs]

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!

[SinanAkkoyun]

Your channel is pure gold, I'm surprised I didn't find it earlier!

[SenpaiSkyy]

Sweet! The crystal video is finally out! 🍿🍿🍿

[optiondrone]

Les mate excellent effort and excellent explanation, now show us how you cut and polish these KDPs and make Pocket cell out of it.

[WoodenWeaponry]

Amazing work Les! I'll have to get some KDP now I guess 😁

[justanotheranonymous]

+1 to rotary crystallizer future video. Especially if its one that can be 3d printed.