Laser301 Double Beam Effect?

I'm not sure what to make of this one... I have been having an issue with this one dimming shortly after use, and the working time only got shorter. I tried to see what the issue was and on defocusing i would see what appeared to be it dimming, then like cells dividing, another beam appears and moves away from the first... Heres some pictures of the following...





full resolutions shots here: Joeybabcock.me

TEM mode is not 00 with twin beams it is TEM 01 ---probably misaligned or damaged crystals See: https://en.wikipedia.org/wiki/Transverse_mode

You can see explainations in charts and pictures here: https://www.google.com/search?q=TEM+modes&rlz=1T4FUJN_enUS494US494&biw=1335&bih=531&site=webhp&tbm=isch&tbo=u&source=univ&sa=X&ved=0CCkQsARqFQoTCKyw9bvylcYCFcQXrAod_j0A7Q&dpr=1

Encap said:

TEM mode is not 00 with twin beams it is TEM 01 ---probably misaligned or damaged crystals See: https://en.wikipedia.org/wiki/Transverse_mode

You can see explainations in charts and pictures here: https://www.google.com/search?q=TEM+modes&rlz=1T4FUJN_enUS494US494&biw=1335&bih=531&site=webhp&tbm=isch&tbo=u&source=univ&sa=X&ved=0CCkQsARqFQoTCKyw9bvylcYCFcQXrAod_j0A7Q&dpr=1

Click to expand...

Thats what i originally thought, im just confused because it starts off tem00

joeybab3 said:

Thats what i originally thought, im just confused because it starts off tem00

Click to expand...

I imagine it's temperature related. Crystals could be shifting with the change in temperature, I doubt it's a thermal lensing issue at those powers.

This issue with the double beam has come up here before with 532nm greens. I remember reading this can easily happen with DPSS lasers, something to do with the crystals and optics.

Alan

Due to temperature changes, the crystals in the laser deform and can cause a second gain area to form. (the difference in crystal size is really small, invisible to your naked eyes) Once the crystals stabilize the crystals stop changing shape and the beams merge into one beam again.

doubleone44 said:

Due to temperature changes, the crystals in the laser deform and can cause a second gain area to form. (the difference in crystal size is really small, invisible to your naked eyes) Once the crystals stabilize the crystals stop changing shape and the beams merge into one beam again.

Click to expand...

What you are talking about here is "Thermal Lensing" which is caused by a temperature gradient in the crystal, it's something that can be hard to design for in high power systems.

There are several causes for non TEM00 operation though, for example a change in temperature can cause the metal housing to expand/contract and as a result the crystals end up out of alignment just enough to shift the output from TEM00 to some other mode. Sub par quality pump beams and low quality optics as well as bad alignment from the factory can cause similar issues.