PHR at 115mA Brighter than PHR at 150mA?

[691175002]

I've read people talking about high efficiency diodes and the wavelength variation among diodes but this is almost ridiculous. Right from the start it was clear that this diode was brighter than the other one, when both were running at ~100mA this one had a visible beam while the other was very faint. I don't want to destroy the better diode so I have been reluctant to push it up, but I stuck the other one in a big heatsink and turned the current up. While it became brighter, it is still no where near the level of the other diode, when they are beside each other the 115mA beam completely overpowers the 150mA beam. I have no reason to believe that the diode is damaged, both burn fine. Is this normal?

 

[jayrob]

You have found one of the highly coveted longer wavelength PHR's!

I have several of these myself...

No reason to push a diode like this! Keep it at the lower current so it will last a long time...
Jay

P.S. I found a 6X like that too! 171mW's and way brighter (visually) than my 209mW 6X build!

 

[Kage]

I've read people talking about high efficiency diodes and the wavelength variation among diodes but this is almost ridiculous. Right from the start it was clear that this diode was brighter than the other one, when both were running at ~100mA this one had a visible beam while the other was very faint. I don't want to destroy the better diode so I have been reluctant to push it up, but I stuck the other one in a big heatsink and turned the current up. While it became brighter, it is still no where near the level of the other diode, when they are beside each other the 115mA beam completely overpowers the 150mA beam. I have no reason to believe that the diode is damaged, both burn fine. Is this normal?

If you consider that 405nM is right at the borderline of visibility to the human eye, just a small variation in wavelength makes a big difference in visibility, so while it may seem ridiculous, it really isn't

 

[Benm]

Indeed, its just product variation. Value those with longer wavelength, they are much nicer visually.

One other effect is that wavelength will come down when you run the laser diode warm, so increasing current could have a more then proportional effect on visible power.

Badly cooled red diodes suffer from the reverse effect: if you increase the power, temperature rises and apparent brightness goes down instead of up. Burning power does go up though.

 

[691175002]

I did some math using a diffraction grating and the diode has a 1.5cm greater spread than the other blu-ray over ~2 meters which puts it at approximately 5-8nm higher than the other diode.

Note that the math also puts the good diode at 406nm and the bad one at 399nm which suggests that its more the second diode being shorter than this one being longer. This was all done by crawling around with an inaccurate yard stick so both numbers are up to scrutiny though.

 

[Benm]

Oh well, even if the absolute numbers are off a bit, it proves the point anyway.

I wouldn't call it good versus bad though, a shorter wavelength might be more interesting for fluorescing stuff. Around 400 nm they will always appear very very dim compared to even a 670 nm of the same power - its just what our eyes do with it.