Electronic – Why is a laser supply so tricky

constant-currentlaser

I need to build supply for ~20 laser diodes (~150 mW each), and the question is why can't we just use a constant current power source for each of them?

A similar question for pulsed mode operation: if I would need, let's say, 50 ns pulses, is it correct that I just need to stabilize the current in these periods or is it again more complex?

Can it work this way: We start from, let's say, a 1.5 V supply, use a FET to connect diode to the supply for 50 ns and sense the peak current. Then we slowly increase the supply until we reach the required peak current. Will that work?

Any practical experience? Any comments on the last paragraph?

Best Answer

Can it work this way: We start from, let's say, a 1.5 V supply, use a FET to connect diode to the supply for 50 ns and sense the peak current. Then we slowly increase the supply until we reach the required peak current. Will that work?

Yes it will work, but if it gets too much current you may burn it out, to little current and it will not lase. Max current is usually 10 to 15 percent above its min lase current.(depends on laser)

some good info here and an interesting chapter here and full table of contentsthey also have some driver references and schematics

I learned a lot from that site about how to drive some re-purposed red laser diodes that I had laying around.

I personally would start off with the lowest current possible, move it up till it lases and then calculate 10% above lasing current and make that your safe constant current, pulsed current can be higher.

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