How did I do this?

Holomark · Post by **Holomark** » Mon Jun 10, 2013 10:13 pm

I was trying out a new layout on my table and somehow got this:

: Beam banding; Beam issue - banding.JPG (16.12 KiB) Viewed 9159 times

Not sure what caused this. I tried changing out various optics in path, but couldnt find the culprit.
But for the loss of part of one of my beams the setup worked well.
Any thoughts?

holomaker · Post by **holomaker** » Tue Jun 11, 2013 5:36 am

Somthing in optical path , clean exit window ,try to lower output to see if it goes away ...............could be a side mode showing up too.

BobH · Post by **BobH** » Tue Jun 11, 2013 8:31 am

Edge of a card or something touching the beam? Back reflection off a component going back into the laser?

Dinesh · Post by **Dinesh** » Tue Jun 11, 2013 9:53 am

Could be a back reflection interfering with itself. It looks like an interference pattern of two beams since the fringe structure exists throughout the spot, as opposed to only one edge of the spot showing lines. The spatial frequency is constant across the spot, so the two interfering beams are almost inline, which implies direct back reflection form perhaps a beamsplitter.

Holomark · Post by **Holomark** » Tue Jun 11, 2013 4:06 pm

Thank you all for the comments.
I have since taken this setup of my table and replaced with a completely different setup. I do not have the problem with the current setup (or prior setups). I suspect that the suggestions that there was some back reflection causing the problem is the answer. At least I now have a better idea of what to look for if I do see a similar problem. Some day when I am bored I will try the same table layout again and see if the problem comes back.
Thank you all.