>      My question: What exactly the circuit on the PCB of a laser diode
> module does? It seens to be a simple current regulator.

Could be, if it's a two-legged diode. Three-legged diodes have a monitor
photodiode so you can build a closed loop circuit.

>      There are some *cheap* way of measuring 635nm and 532nm laser beam
> power?

Solar cell works quite well.

But wait, you mention 532nm. That's a completely different animal. There
is no 532nm "diode". They are all diode pumped. 880nm diode pumps a 1064nm
laser, then frequency doubled. Expensive, inefficient, and extrememly
sensitive to temperature.


Cheerful regards,

Bob


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