Finding an AOM for 671nm

[weartronics]

I'm trying to build a low-powered RGB projector with excellent beam quality, power stability and modulation ability. I can use it in a dark room, so even 100mW combined optical power output is probably sufficient. I will use 473nm, 532nm, 671nm DPSS lasers to achieve the necessary beam quality. Unfortunately due to thermal effects, diode current modulation of DPSS lasers seems to have terrible power stability and modulation ability. I want to know if it is possible to overcome this using fast optical feedback (e.g. a photodiode with R,G,B filters in the output and PID feedback to the diode current), or if it is necessary to use AOM modulation.

* Have you done any experiment using optical feedback to compensate for thermal effects during DPSS diode current modulation?

* Do you know any commercial projector which incorporates photodiode feedback for DPSS diode current compensation?

* Do you know any commercial projector which incorporates AOMs to modulate the power of DPSS laser sources?

[gogu]

Hello Weartronics,

This AOM should do 671nm, ISOMET 1205C-1/2
Standard Operating Wavelengths: 442-488nm, 488-633nm, 633-830nm
http://www.isomet.com/FinalWebSite/P...1205C-1(2).pdf

[FourDee]

SOMEONE was doing the optical feedback experiment around here. I think it was about a half a year ago. I don't remember who though.

He even managed to use only one photodiode ...

[mixedgas]

SOMEONE was doing the optical feedback experiment around here. I think it was about a half a year ago. I don't remember who though.

He even managed to use only one photodiode ...

Four of us started on, it but day jobs get in the way....

He should use pulse width modulated AOMs

Steve

[fuzcub]

* Have you done any experiment using optical feedback to compensate for thermal effects during DPSS diode current modulation?

Played around a bit with a feedback loop ,but ran out of steam.
My main goal was to have fine control at the low end of my 532nm laser
(when colourmixing red and green the diffference between orange/gold/yellow is only a few percent) . My problem was that to have enough sensitivity to a few mw of green seriously saturated my photodiode when the laser got up halfway to 500mw.

* Do you know any commercial projector which incorporates photodiode feedback for DPSS diode current compensation?

EyeMagic make a module as an add-in which does this:
http://www.eyemagic.gr/laser-iris-colorsafe.html
The board also functions as a safety device , using the feedback from the laser detector to control the exposure projected into the "safe" zone. So rather than chopping the beam off entirely, it can dim the beam to the correct brightness given it actually knows what the instantaneous intensity is rather than some wobbly voltage to brightness relationship.

* Do you know any commercial projector which incorporates AOMs to modulate the power of DPSS laser sources?

RGB LaserSystem were working on a high power, high stability laser that used a chunky big DPSS running CW with an AOM for modulation up to 100khz ( and 0.2mrad) but I think coherent OPSL and jenoptik thin disk lasers stole the thunder somewhat.
B

[buffo]

DZ is working on a prototype feedback board to solve this very problem. He's achieved excellent results so far. Don't know how close he is to a final product though.

Adam