Diode pump a ruby laser?

EBEOS said:

My name is Walter Luhs. I am the owner and creator of all laser kits on https://luhs.de.
I am holding a degree as engineer, physicist and PHD in physics (Photonics) since 1983.

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Welcome EBEOS. Being a new member you might not have read through these two threads. They generated quite a buzz do to the color of these two lasers and to their simple construction. But there's an unsolved mystery which is specifically what type of crystal. What we know is a self frequency doubling crystal is used. If you have anything to add please do so in those threads. https://laserpointerforums.com/threads/565nm-dpss-labby.102862/

https://laserpointerforums.com/threads/574nm-36-mw-yellow-laser.102893/

Benm said:

But that rod is not lasing there. It does produce a red dot, but i'm sure it's not monochromatic, it's just fluorescing.

This is perhaps similar to a laser diode running below it's lasing threshold current: in produces light like an LED or something similar, but not monochromatic or collimated. If you'd put an optical cavity around that rod that would allow lasing using a flash lamp as the pump, i'm quite sure it would not lase using any of the setups you displayed.

Nice photo's none the less!

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Don’t worry Benm, I’m fully aware the rod is not lasing in those pictures. I’m just demonstrating it’s activity with some of the wavelengths.

I'm not... the idea is interesting though: could it be possible to pump a ruby rod like that with diode lasers if you go to the extreme, like surrounding the rod with hundreds of diodes from all sides and along the entire length as to get it evenly lit, and fire them in pulse mode just to get the thing to lase at all?

I'd be interested to see something like that, though i presume using the xenon flash in a cavity setup would be a lot cheaper to build.

Yeah, it's technically possible, just exceptionally hard. Ruby by nature doesn't lase CW, and even when you can coax it to never stop lasing, the power still is kinda a pseudo pulse. It has to be cooled quite a bit to force enough depopulation of the upper states to keep any output going. Although a well pulsed array with diodes might be interesting to try sometime. You could set up a large array of diodes on slow 3ms pulses every 10s or so apart and probably manage it presuming you can find mirrors. problem is a fully pumped ruby tends to blow apart metallic mirrors over time, and good dielectric ones are impossible to find. My old commercial one actually has no mirrors at all, and instead uses a turnaround prism as the HR, and a series of glass or sapphire plates that are configured like an etalon of sorts to work as the OC for reliability. (in theory) the rod is a couple inches long and pumped by two linear xenon lamps, and has an old mechanical q switch. it's quite fancy.