Mystery crystal growth. More efficient DPSS process using KDP.

[CurtisOliver]

Hi everyone, I have come across an article by NIST.
It has sparked interest in me as it could allow more efficient and higher power yielding for 532nm DPSS's.
As well as the possibility of allowing more DPSS wavelengths to become a reality. They use KDP which is grown in a rather exotic way of which scientists can't explain yet. Neither can they explain why it even works efficiently. :thinking:

This section of the article is good news for the future.

The team also suggests the rods could be stacked up like firewood, building a larger piece out of billions of the tiny filaments. Before they are stacked together they could be coated by a thin layer of conductive material that carries heat away, rendering them capable of handling repeated pulses of high-intensity laser light – potentially broadening their application range if a way can be found to stack them.

No more efficient but low power handling KTP. Instead high power handling, low cost and efficient KDP. We can only dream

I am going to include links to both the NIST article and the paper it references. If anyone is interested in reading into the articles, feel free to report back your thoughts.

NIST Article
Paper

 

[diachi]

Interesting - hopefully that'll trickle down to us . I don't imagine a batch of those fancy new crystals would be cheap ... or even one of those fancy new crystals.

That said ... it doesn't sound like it'd have much benefit for pointers. More useful for big Q-Switched lasers and other high peak power pulsed lasers by the sound of things.

 

[H2Oxide]

Huh.

What's interesting is that they're using KDP, rather than the typically preferred KD*P. And, if my understanding is correct (only had time for a quick skim of the paper), these can be grown at home (KDP is water-soluble). If this pans out it could result in a huge price reduction of frequency doublers for us hobbyists.

I just finished my second batch of KDP crystals a few days ago, and since I have some temperature control stuff on the way anyway I might try growing these.

 

[HydroSean]

This reminds me of how no one can explain why the second derivative of the critical micelle concentration of amphiphiles with respect to temperature is positive. In other words the critical micelle concentration decreases with temperature as it is predicted to, but at a certain low temperature it suddenly starts to increase and no one knows why. I remember my professor saying that a lot of "hand-waving" goes on at this point, where they just agree to disagree on the exact mechanism. I think this applies to the KDP initial crystal growth but I can propose my own theory. It is known that the only reason crystals grow in a saturated solution is because the formation is favorable by decreasing the amount of Gibb's free energy. The mechanism for simplistic crystals forming out of super saturated solutions starts with either a seed crystal or a nucleation event. Given that these are highly pure and controlled experiments I am going to assume that they do not use a seed crystal, this means that the nucleation event must be the kinetic product of two KDP molecules colliding as the super saturated solution cools down. From this kinetic product, although disfavorable to the thermodynamic product, it is necessary to create this nucleation event. I hypothesize that the kinetic product causes the formation of these hexagonal rods. I would need to see the ball-and-stick model as well as the space filling diagram of the KDP rods to further hypothesize the crystal formation mechanism. Although the mechanism eludes us, the data is still there so we can just "hand-wave" for the time being and focus on the development and use of this technology. As far as growing them in large arrays with uniform cross-sections goes, I know in the past scientists have employed rods on the growing medium to facilitate a less amorphous product crystal like the one in this article. https://www.researchgate.net/publication/228030454_Hydrothermal_Growth_Polymer-Templated_Hydrothermal_Growth_of_Vertically_Aligned_Single-Crystal_ZnO_Nanorods_and_Morphological_Transformations_Using_Structural_Polarity_Adv_Funct_Mater_182010
Perhaps they can use something like that to achieve a more uniform crystalline product.

Good article though and great read