5mW green laser pointer has rings around dot

[Assainator75]

I was playing around with my green laser and noticed that the green dot wasn't exactly a single dot of green. It had around 2-3 uncollimated green rings around the center dot... Is this normal? Mode hopping? Something out of place?  Doesn't seem like much of a problem, but I'd like to know if anything is wrong with it.  :-/

 

[diachi]

I was playing around with my green laser and noticed that the green dot wasn't exactly a single dot of green. It had around 2-3 uncollimated green rings around the center dot... Is this normal? Mode hopping? Something out of place?  Doesn't seem like much of a problem, but I'd like to know if anything is wrong with it.  :-/

Could you give us a picture of the dot, that would help a lot Could be mode hopping, could be something on the lens, could be something else though :-?

-Adam

 

[Assainator75]

I'll try to get a picture, when I can get my camera... but I've made a rough sketch on "paint" of what it looks like when pointed at a piece of paper.

 

[RA_pierce]

It's either a dirty lens or part of the beam is reflecting off of the aperture or lens (which could be caused by mode hopping).

To check if it is switching modes, project the beam onto a wall with a magnifying lens. If the beam looks like anything other than a single dot, it is probably not in TEM00.

 

[styropyro]

This is most likely a little bit of dirt on one of the lenses inside the laser. This is typical with cheap lasers, and if it doesn't bother you much it shouldn't be a problem. I have a couple lasers that have these hard to notice circles of light around the dot.