DPSS laser - two beams?

[carmangary]

I have a green DPSS 50mw laser. I was messing with it and noticed that I had two spots close together and realized I had two beams coming out of it. Then, the next time I turned it on they were gone. I was messing with the current levels during all of this. Can anyone explain what might have been going on?

[The_Doctor]

Sounds like a clean TEM01 mode. Not sure though. The laser is probably driven by a multimode pump diode, so if the active region widened with extra input energy, a similar widening of active region would happen in the vanadate, which could be enough to make it go from TEM00 to TEM01.

[carmangary]

No idea what you're talking about, Doc.

[Laser Ben]

Essentually what it is, is when the cavity on the MCA warps due to heat. It can still lase but the beams come out at different angles. Here's a wikipedia page on it: http://en.wikipedia.org/wiki/Transverse_mode

[carmangary]

That's interesting stuff. Although, I was running the laser well below normal current when I saw it happening. Once I increased power it went back to normal. So that makes me wonder about it warping due to heat like you said.

[Laser Ben]

This can also happen because of low temp, it may be that when you turn on the laser it quickly increases heat and goes to TEM00, if you are running it at a low current then it might be too cold. Try slowly changing the temperatire of the laser by holding it in your hands when you turn it on at lo currnet.