I'll have to try that as well!
EDIT: Tried it...don't understand. :/
Hey bloompyle, I think he's talking about
laser speckle. It's a visual artifact resulting from the random interference within a diffuse reflection. It's easiest to see when viewing a larger spot (like an expanded beam, or one at a distance from the laser), on a matte surface like cardboard, paper, or a surface painted with a flat finish paint.
BTW, I've checked out your gas laser threads, and learned quite a bit from them. Thanks.
Hey Norbyx, that's a REAL NICE HeNe you got there! That kind of power is impressive for that particular tube. If you want to see if it is going multimode, you can best see it by viewing the spot at a distance, or expanding it with a lens (much like I described above^^^ for viewing laser speckle).
I have a very old soft-sealed tube that modes like crazy, but it never occurred to me to monitor the output power while watching it. I'll try to dig it out and do that when I have time. It might be interesting.