Green laser power drop off question

[CHP]

I have a mod green laser (4.99mW) from Z-bolt. When I received the laser the power supply drew 182 mA and using the green LED I measured about 13 uA. I tweaked the pot until the supply current was 235 mA and using the green LED I measured about 55uA. Now if I increase the current to 250 mA and I let the laser run for a 1-2 minutes I will see a sudden power drop off (output reduces about in half according to the green LED). I'll let the laser cool for ~10 seconds and then turn it back on and after ~5 seconds I see an immediate power drop off again. It seems that it can run all day at 235 mA but not 250mA. The power drop off seems thermal related. I'm looking for some feedback about the possible causes of this (i.e. thermal expansion changing alignment, LD power drop off, etc.).

 

[Spec]

Back to diode efficiency:

The diodes ability to produce 808nM depends heavily apon the temperature of the diode, I remember reading somewhere that it operates best between 26-29 degrees.

I made reference to frequency drift in a previous thread, this is a prime example of this due to thermal contstraints.

-Spec

 

[CHP]

I think you are right Spec. I'm looking at the datasheet for the sony LD and I can see a wavelength increase due to temperature and output power. Perhaps mine was on the 808 nm edge and due to the higher output power and temperature my LD wavelength grew too much. I guess if I want more power I'll have to run at a lower duty cycle.

 

[CHP]

The other thing is the polarization ratio change with output power. Maybe I should rotate the LD too.