532 DPSS vs 520 DI

[Draco]

I have allways wondered if i would notice the difference, me and my friends see, to argue about how a certain color looks to different people, all crap is ttl . i don't have a real easy way to modulate the optical power, i like the satble powerfrom the crystal lasers but the have low output power, 25mw, i can get 60 out of one if i disable the feed back loop but i don't know the rating of the pump diode, i have allways loved the blue dpss lasers and have a cavity from one that i cant get the damn thing to lase, i think my pump diode of not the correct wavelength for that set up, what should the pump wavelength be for a blue dpss ?

[buffo]

Pump wavelength is the same for DPSS blue and DPSS green (808 nm). The difference is in the coatings.

For green you want the Vanadate to lase at 1064 nm, but for blue you need the 946 nm line to lase. So the coatings need to be optimized for that 946 line (and they need to kill the 1064 line since otherwise it will compete preferentially). Then too, since the 946 nm line has far lower gain, you need a bigger pump diode for the same output.

I should point out that there is another difference: the doubling crystal. Most dpss blue lasers use BiBO or LiBO, whereas most dpss green lasers use KTP.

Tinkering around with a DPSS green laser isn't that difficult (assuming lower power units here; if you're working on a 3-5 watt unit they are every bit as complicated as a DPSS blue). Most hobbyists can successfully disassemble and reassemble the cavity and get it to produce green.

Try the same thing with a DPSS blue and you will find it is a LOT more difficult to get it back together in a working state. For one, the gain is a lot lower, so any slight misalignment in the cavity is going to have big consequences. Then too, both LiBO and BiBO (the materials used in the doubling crystals) are hygroscopic. If they absorb too much moisture from the air while you have the cavity open, they will be ruined. No doubling crystal means no blue output.

Adam

[SaltyRobot]

Then too, both LiBO and BiBO (the materials used in the doubling crystals) are hygroscopic. If they absorb too much moisture from the air while you have the cavity open, they will be ruined. No doubling crystal means no blue output.

Adam

bismuth triborate (BiBO) is not hygroscopic the older Barium Borate (BBO) and Litium triborate are both hygroscopic. The BiBO is also more efficient that is why you will find those crystals in the newer DPSS Blue. It still doesn't change the fact that aligning the cavity is much harder than a DPSS green.

[buffo]

You're right, Jason! I conflated BBO with BiBO. My bad!

Adam