suitable voltage for a 20mw 405nm laser diode?

[gus_gus1207]

i recently bought a couple of 20mw 405nm laser diodes to tinker around with (i’m a newcomer to lasers so i really don’t know what i’m doing) and the seller said that the working voltage is 4.7 volts. i built an lm317 constant current regulator with and output of 4.7 volts and the laser is very dim. i also hooked the diode up to 8 volts and it worked, was very bright but then died could someone give me an ideal voltage for the diode? thanks in advance !

 

[paul1598419]

Laser diodes need to be current regulated. You should never just hook one up to a voltage source as that is the fastest way to kill one. The 405nm diodes tend to have a fairly high forward voltage, usually higher than 4.5 volts, but the current it is allowed to pull is regulated by the laser driver. These can be constant or adjustable, depending on what you want. If it is adjustable you will need a dummy load to use on the driver to set it up for the amount of current you want it limited to.

 

[diachi]

Also, 20mW of 405nm is going to be really dim anyway, so depending on how you define "dim" that could be perfectly normal.

 

[Alaskan]

Oh ya, very dim, that short wavelength is only a couple of percent as bright as 532 nm green at the same power, if that. Depends if looking at the beam from the side or the spot produced by it; 1-2%.