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Is there a simple circuit solution for this?
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ballen:
Device is packaged in a small metal cylinder with an adjustable focusing lens and a red and black lead coming out the back.  I don't think I can see what's inside without destructive disassembly  :(
magic:
Well, nevermind then. Mine was like shown below and yours is probably similar if it maintains constant current.

Actually, with one difference. I think R2 was some sort of a thermistor originally, but I damaged it while replacing power leads and installed a fixed resistor instead.
RJSV:
Let me see if I got this right, please:
   You present a question: "...need proper fixed VOLTAGE..."
"...for a FIXED load...".   NO, it's not a fixed load: it's a semiconductor.
   After which a likely very experienced reply comes:
   "...don't connect directly to a voltage..."

  So, you then proceed to another possibility: A VOLTAGE, this time created by a zener, followed by an inevitable reply, explicitly warning:  "laser diode is a current-controlled device.."
Generous with advice, that reply also mentions things (like necessary VOLTAGE) 'can vary a lot, with temperature..."
   THEN you introduce another LDO regulator option and focus on... wait for it: VOLTAGE output to laser diode.
Granted, of course you have to ensure the headroom is sufficient, there.
To which, the predictable reply ends with:
'...to make a constant current sourc, e...'.
   You then further 'experiment' with drive VOLTAGE, even mentioning  current NOT constant, a little. (Whatever that means), 'happily' working, (and again, at whatever the device temperature was then...who cares?)

And yet, yet, again REPLY comes: to focus on 'current setting', for a temperature-dependant semi-conductor load.
Ok, I'm done.
Set your sights on 'device current'!!!
  I made that mis-step a bunch of times, (tried voltage controls).
NiHaoMike:
A MOSFET current sink can have close to zero voltage drop.
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