Green laser problem?

[Things]

I decided to graph my laser scanners total output. It started off great! I was happy!. Then all of a sudden, the power dropped dramatically. I instantly suspected my green laser (DPSS of course). My graphs confirmed it

It seems like a heat issue. The laser body itself doesnt even change temp while it's running, however it seems maybe the TEC on the diode (It's a lasercentury module, I think they only TEC the diode?) might be off.

Does this look like a heat problem inside the green laser? There is 3 pots on the driver, my plan was to sit down with the meter graphing continually and adjust the pots every so slightly and se what happens. If it's the current pot, the power will change instantly, but if it's the TEC pot, the output should change slowly.

Unless anyone here knows the pot config on the drivers, it's really my only option to try fix it

All graphs taken after all optics:





The huge instability is partly caused by the ADC.

Cheers,
Dan

[-bart-]

Is that a hours:minutes:seconds or a minutes:seconds:hundredths timeline ?

[Things]

Hours:minutes:seconds

The red laser was only graphed for 1 min, since it's diode based it doesnt vary much.

I'm going to open er up this afternoon and start fiddling with some pots to find out what they are for. I'll let the laser settle at it's power power and adjust the pots until it's nice and stable at a higher power.

IIRC there is only 1 TEC in this laser on the diode, if so, what would the 3rd potentiometer be for? Modulation threshold?Overtemp?Optical feedback?

[Things]

After a few hours tweaking the potentiometers, I have managed to get it to idle at double the power!

It still seems to have a rather sharp dropoff a few minutes after startup, but I'm happy with it at 127mW avg

[-bart-]

It might be wise to optimise for max power when applying a modulated signal.
Continuously 100% on is not a realistic setting, for laser display.

[Things]

Thats true, however the refresh rate of my meter wouldn't be high enough to measure each pulse.

Basically I adjusted the 2 unkown potentiometers until it worked the best (Stability and power), then just adjusted the diode current a teeny bit. It's been idling nice and stable at 178mW for the last 10 minutes, so I'm gonna leave it for another 20 mins or so and see what it does. The modulation shouldn't affect the tuning too much, as the temp remains constant the whole time anyway. I do know it lowers the power though, but it's not really possible for me to tune for it with this meter

[-bart-]

You don't need a fast meter to temp-tune your laser when modulated. You just have optimise the overall power that leaves your module.

The integrating thermopile effect is just what you want.