LPM Request (Free diode!)

[Insomniac]

I was playing around with a second unit in an Aixiz housing today, and noticed something interesting. This diode seems *very* temperature sensitive. I was holding the module in my hand, which also happened to be somewhat close to a small heater in my room. The combination of my hand and the warm air heating up the module caused the output to dim to almost nothing. The dot looked similar to cheap lasers which have been damaged by overcurrent. I was convinced the diode had died, but upon putting it in the fridge to cool down, the output was restored.

Is this typical with diode lasers? I haven't noticed my cheap 650nm modules being quite so sensitive.

 

[The Lightning Stalker]

It was probably overheating. I also noticed these diodes run quite hot if they are driven just below
threshold. When the unit I had was working, it would start heating fast at 10mA, but ran cool even at
45mA. It was in the 15mm aluminum AixiZ module and also on a decent heatsink, so there was quite a
bit more thermal mass and thermal conductivity than in the standard brass AixiZ module.

I have also heard that the 2 transistor regulator circuit is temperature sensitive, though I haven't tested this
yet myself.

 

[The Lightning Stalker]

No, I didn't forget. I FINALLY got around to doing
some more testing on these diodes. After some
fancy pants maneuvers with tweezers to remove
someone's extremely fine "?" hair, diode #2 once
again had very similar results. It hits lasing
threshold around 25mA and reaches 5mW at around
36mA with a standard AixiZ uncoated acrylic turned
all the way in. It was still clipping the beam and
losing some output. Best results will be had with a
short focal length lens.

I also did some wavelength testing. The center
wavelength tests at around 643nm. The spectral
linewidth is quite wide, covering about 5nm. There
are several longitudinal modes which I could just
barely make out. These are a multimode diode.
Despite this, they focus quite well.

 

[Insomniac]

Very interesting, thanks for testing.

I'm surprised at the wavelength. Mine is very visibly more orange than my 650nm pens, which I find curious given the similar wavelength.

 

[The Lightning Stalker]

They are definitely more orange, and definitely
appear brighter per mW. We are still talking about a
7nm difference (probably more like 17nm because
most "650nm" diodes are actually 660nm). This
particular diode could also just be on the higher end
of the wavelength range. I do have one more I could
give a test to see if it is more orange than this one.