daguin said:
Without TEC, in a hand held, I drive them easily to 140mW after optics. Above that I start limiting the duty cycle. With TEC, you should be able to push them above 160mW without a duty cycle. I have them running in hand held at 185mW (200mA input, passive heat sink, limited duty cycle). I would love to see what they can do with active cooling.
I do not believe heat is the killer here... Not if you're using ANY kind of heatsink.
The normal operation temperature is 75°C for diodes like these. That's when using them within their ratings of course, which no one here is doing, but still, even at 190mA, my laser hardly went above body temperature after an hour.
A TEC would do one thing - stabilize the output power. (Of course only if the TEC is powered by a constant temperature driver, otherwise it'll always drift in one direction). It can also make the power higher. But it will not necesarily make the diode live longer.
Because of the higher power, the TEC could actually make a diode die faster. It's the optical flux at the die, that kills them. So a diode, that is not heatsinked enough (but also not too little) and heats up a little more, could actually live longer, simply, because it's output power would be lower most of the time..
This is also the reason why a short duty cycle might not matter much, if you have enough heatsinking. Duty cycle is only important, when a laser is overheating, and you need to let it cool down, because the heat is getting so high, that it could actually cause damage..
One thing a duty cycle might indirectly cause, is reduce the total amount of time you use the laser per day. I have my experimental units on for around an hour a day, sometimes more. Either i leave them on and measure the temperature with an IR thermometer, or i simply play with it for 20-30 minutes without a break at night. Maybe that's why my freaks died.. More total use?
At least that's what laser theory says.. I have some high efficiency constant temperature buck peltier drivers, but ran out of diodes good enough to test it.. And the new ones just arrived at the customs today..
But i would slowly like to stop the destructive testing. :
