532nm Laser Module
This is one of a few 532nm laser modules I picked up on eBay, from memory output power was measured in the low 100s of mWs using the optical power meters I previously wrote about.
This unit had a mechanical failure (the leg staped off the diode). So I decided to pull it apart. For a cheap eBay module, it’s pretty well made:
The driver uses an LM358, which from some brief googling seems to be pretty common in these small laser pen boards. This opamp is used to create a constant current source. The current is set via the small variable resistor/pot to the right. This is often used in combination with a zener reference, but I don’t see one of this board. I guess they must be used a voltage divider.. which is less precise but I suspect the vendor isn’t overly concerned about meeting stability specs…
I assume driving current via one of the transistors which you can see on the rear side of the board:
Further pulling apart the optics you can find the doubling medium. From Brainiac75’s experiments with these lasers, many of them appear to use 800nm IR laser diodes. The doubling mediums appear to be YVO4 and KTP.
So, the IR light heads out of the diode and into the doubling medium(s), which convert it to 532nm light on the output.
As Brainiac75 points out, this can cause issues because the doubling mediums only work over a limited temperature range, but the IR diode works over a much wider range. This means on a cold day, the laser can be outputting relatively high power invisible IR laser light.
That’s it for today! Have fun and remember: Do not look into laser with remaining eye!
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