Dirty HeNe?

erose · Post by **erose** » Thu Dec 16, 2010 8:20 pm

I am having trouble getting a good clean beam spread with my SP 10mw HeNe and spatial filter. I have used spatial filters in the past with other lasers and know what I should be getting. The laser is a good 20 years old and back then it was used as much for mood (don't ask) lighting as holography. I am worried that some particulate matter may be on the output mirror. Any suggestions for troubleshooting would be appreciated. I see 3 variables: laser, pin hole and objective lens. Where would you start?

holorefugee · Post by **holorefugee** » Thu Dec 16, 2010 8:33 pm

http://www.holowiki.org/index.php?title=Spatial_Filter

BobH · Post by **BobH** » Thu Dec 16, 2010 8:50 pm

How difficult is it to get at the output coupler face? The beam is very small coming through the OC, and centered. Make a tiny little pad of paper (like 1/2 the diameter of the OC), hold it with the tiniest long skinny tweezers you can get or make, and give the OC a few wipes with acetone. Use the smallest possible drop of acetone. Use the paper pad for only one wipe. Be reeeeaaallllll careful you don't hit the surface with the tip of the tweezers!!!!!!

Johnfp · Post by **Johnfp** » Fri Dec 17, 2010 8:57 am

If you could post a photo of your laser and the spread output beam, it would be most helpful.

I personally try a very short quick blast of air first. If its a loose speck of dirt it may dislodge.