Doubled laser?

[Mille]

Sorry but i cant take a picture of it.
I noticed that lately my green laser is doubled in vertical lines.
I dont know how to explain: when a line draw on wall by scanner is vertical, instead of a single line you see two parallel lines, spaced by some millimetre.
Or maybe can be some millimetre of blanking in the centre of vertical lines.
The artifact is not revealed on orizontal lines.
I cant see the problem on red laser cause probabily is a fat beam and you cant see the blanking space inside.

Anyone ever heard of this?

[uk-laser]

Sounds like the laser may no longer be TEM00. (Perhaps now TEM01 / TEM 10 ?)
http://en.wikipedia.org/wiki/File:Hermite-gaussian.png
Was this accompanied by a drop in o/p power as well?

[shrad]

could also be one of the galvos which is beginning to die and vibrate?

or oscillation on the galvo amp?

[fuzcub]

If it's no longer stable in TEM00, if you fade the brightness of the beam slowly up and down while scanning , you should see the double beam changing (morphing between modes) . Otherwise could it be a double reflection off an uncoated side of a steering mirror or dichroic combining optic? Barney.

[Mille]

Thanks for the replies.
Seems like TEM 10, but need to check it more accurately.
IF the brightness is low, the blank in the middle of the vertical line seems more accentuated.
...ora maybe is one of the galvos mounted on wrong side...

I will check better when i come back from work.

[Laserman532]

take a simple magnifying glass and expand the green only beam to a big spot on the wall and you will see what mode it is.

[Mille]

Ok i checked the green module alone and the mode is TEM 01.
What caused this?
And theres nothing i can do before to ask for a repair? (module is in warranty time)

[MechEng3]

Possible shift in the diode or crystals...what brand of laser is it? Have you monitored the temperature of the TEC's inside? I have seen a few strange things....it could be a mode shift due to temp changes...or a result of an ESD event showing up.

[Mille]

The Module is a Laserwave >300mW.
I don't think i ever used improperly: i don't have a thermal control, but i never used it in a closed case (i'm near to finish it and stil need to mount fans).
The temperature of module was always just a little warm and never hot, so maybe is another kind of problem.

Btw i will contact bridge, cause i dont think theres anything i can do to fix it by myself (and above all the laser is still in warranty).

Thanks for Help.

[mccarrot]

Have you checked after 15 minutes.

Allot od DPSS lasers start lasing in TEM 01 or 10 and after they are warmed up (or cooled) they are fine.

My blue CNI is also tem01 the first few minutes, and after 5 minutes it reaches full power.