That is a Cr:YAG passive Q-switch, aka a saturable absorber. The dark green color gives it away. Odds are the rear mirror is NOT coated on the Q-Switch.
The laser will work best if the flashlamp is fed from a pulse forming network. If you don't use a PFN and the rod lases near it's edge, ie long pulse mode, it could crack there. If I were playing with this I would use an intracavity pinhole to keep the beam in the center of the rod until I was sure it was properly aligned.
I used to service scientific ND:YAG. Be really careful with this wavelength and energy . Eye Damage and Tissue Damage are very easy to obtain, even with just stray light. You need safety glasses with OD6 or OD7 at 1064 nm. NOT a toy, and study up on your laser safety, and keep unprotected friends and the family pet out of the room. Nominal ocular hazard distance would easily be in the hundreds of meters for a direct beam.
Keep your rep rate well below a few Hertz or you'll risk melting the lamp and/or shattering the rod/Q-switch.
Buffo, treat this as a hopped up, low quality SSY1, think 5 mJ to 10s of millijoules, and say 20-50 nanosecond pulse if it goes in one pulse train, which is not always likely.
I'm not seeing a rod, and I do not see end mirrors, in the one picture I can see. I'd start with a flat 100% HR and a 5% or 10% OC with a long radius, ie 60 or 100 cm OC or longer.. Eventually you may be talking about a transmittance of 20-30% for full power extraction. I would NOT use a flat-flat cavity with this laser. You'd need mirror mounts, a bench for the cavity, a PFN and a series injection ignitor with a very high energy blocking diode. . Something like a Thorlabs DET-10 and a 100+ Mhz oscilloscope to monitor the Q-switch performance.
Calculating the PSU capacitor for the lamp requires removing the lamp and making measurments and some assumptions about the lamp fill pressure. The rod needs very clean cooling water held at a constant temperature for best performance. John Goncz's paper on flashlamps is needed for the calculations, but Sam Goldwasser and Don Kliepstien (Spelling?) have the math on line some place.
You need access to a a copy of Walter Koechner's Solid State Lasers text book just to get started on understanding this beast.
Without knowing the initial T and Doping of the Q-Switch, designing for this puppy means making a lot of assumptions.
Lamp voltage with the right PFN may be anywhere from 250 to 750 volts, and that is a big unknown. Your lamp's explosion energy will have to be calculated as well. Overdriving it is as bad as under-driving it, if not worse. There is a region where it will like to work and a region past that where it will just heat up the rod and energy will go down.
Assuming you use ND:YAG you want your PFN to drive the lamp for just around say 275 -350 microseconds or the laser will act weird and the Q-switch might fire multiple times with VERY low pulse energy, if it fires at all. The laser rod will be saturated in about 256 microseconds, aka 1 storage lifetime.
Your best bet is to find what it came out of, and its resonant capacitor charging supply, rod, ignitor, and supporting parts.
"OSR" has spoken. (pun on earlier conversation in another thread)
PS, The lamp mounting method suggests this is a somewhat disposable module, not really designed for frequent service. See if there are lamp clips under the heat shrink, then replace the heat shrink. If no clips and its welded wire, and the lamp won't remove easily by sliding out, throw it away. Lamps get old, turn black, and become unstable, then can start misfiring or crack.
You may be in for more of a repair job then you think. A good lamp starts at around 150$ and up.
THIS THING IS NOT A TOY. IF THIS IS YOUR FIRST RODEO, AND YOU HAVE THE MONEY TO BUY THE PARTS, THEN GO FIND A LOW POWER CW laser to EXPERiIMENT WITH FIRST.
This also the last way I'd remove a tatoo.. It may be for another medical purpose.
Steve
Last edited by mixedgas; 12-10-2018 at 14:14.
Qui habet Christos, habet Vitam!
I should have rented the space under my name for advertising.
When I still could have...