Practical Info on Ultra-High Q Lasers?

[D Martin]

Greetings,

I am not a laser guy, but I’ve recently found articles on ultra-high Q lasers and grown curious. I’d appreciate directions or links to resources that can answer practical questions like the following (and more) for them The information I’ve found online focuses mostly on theory, which is interesting, but I can’t find real-world information that would also interest someone with grit under his fingernails.

Example Questions:
A) Can they be CW, or must they be pulsed?
B) What are some actual, measured numbers (power out, Q, time to achieve gain saturation, operating temperature, etc.)?
C) What is the average volume of the gain medium and resonant cavity? Are they room-size or will one fit in the palm of my hand?
D) Are all such lasers custom-made, or are commercial manufacturers cranking them out like penny nails?
E) What does one even look like with and without peripheral equipment?

Ultra-high Q lasers seem tremendously interesting. Even if I never get to see one in person, I’d like to understand them practically as well as theoretically.

 

[berkeman]

Welcome to PF.

I’ve recently found articles on ultra-high Q lasers

Links please? Thanks.

 

[DaveE]

The go to guy for high-Q resonators is Kerry Vahalla, my former dorm mate at Caltech, and frankly, one of the most astoundingly intelligent and nicest people I ever met. I'm still grateful for his ultimately pointless attempts to help me with Group Theory. He showed up there out of High School and never left. That is my only useful direction for further information. There's this paper, for example:
https://www.nature.com/articles/s41566-021-00761-7

I doubt you'll find non-technical descriptions. But:

1) I don't know what your background is.

2) High-Q is a relative term and a state of the art "high-Q" semiconductor laser, may have a much lower Q than a 40 year old conventional laser resonator, just because of geometrical things.

3) High-Q probably refers to the resonator, not the whole laser. The power removed from the laser represents a loss term that necessarily limits the overall Q of the system. Yet there are characteristics (like linewidth, output coupling, etc.) that may be mostly determined by just the resonator portion of the design.

4) They could be (probably is) small, a semiconductor laser. However, often with laser systems, you may also want to look at the size of the supporting pieces, power supplies, cooling etc.

5) If people are touting their unique properties, then they aren't being mass produced yet. That's just the way high tech products are. A Pentium uP was an amazing thing once, now it is just another uP that people don't talk about. This especially applies to physics based stuff like a new type of laser. But, really, I don't know; whatever; some laser company marketing guy is probably already writing "High-Q" ad copy right now, even though a 50 year old Nd:YAG Q-switched laser could have a really high-Q resonator.

 

[D Martin]

DaveE,
Your response was exactly what I was hoping for. Thank you. By not assuming that I'm a laser guy (I most certainly am not), you answered in a straightforward way that gives me a way to learn more and, perhaps, ask a more informed question in the future.

I will look for more papers or other contributions from Kerry Vahalla. I’m sure he’s very busy; do you think he would respond if I were to try to contact him directly?

 

[DaveE]

I’m sure he’s very busy; do you think he would respond if I were to try to contact him directly?

IDK, maybe. It probably depends on what you ask him. Frankly, his answer is likely to be to take a couple of years of physics classes. Lasers are complex and there typically aren't simple answers. People often ask questions that they think are simple that just can't be easily answered well. People tend not to want to lie, or insult, or teach you a whole physics course.

I would spend some time just studying basic lasers, which is information you can get online, before you ask about special configurations. i.e. don't ask an expert about "high-Q" semiconductor laser resonators if you don't already know what a resonator is, how simple lasers work, or what Q means.

 

[D Martin]

IDK, maybe. It probably depends on what you ask him. Frankly, his answer is likely to be to take a couple of years of physics classes. Lasers are complex and there typically aren't simple answers. People often ask questions that they think are simple that just can't be easily answered well. People tend not to want to lie, or insult, or teach you a whole physics course.

I would spend some time just studying basic lasers, which is information you can get online, before you ask about special configurations. i.e. don't ask an expert about "high-Q" semiconductor laser resonators if you don't already know what a resonator is, how simple lasers work, or what Q means.

Thank you again for your help. Just having a name to search for opened up much more information for me on YouTube alone, not to mention papers I have yet to peruse. The bonus was that much of it is far more practical than what I had been finding. This should be plenty to satisfy my curiosity.