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GB BR diode - unusual output - Q for the pros

Greyfox

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Sep 25, 2007
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Okay, here's one for the laser chemistry pros. I just completed the build of one of the GB blu-ray diodes, and I noticed that when powering the diode at the very low end (below the commonly reported threshold), this diode was indeed lasing and also putting out non-coherent white light! At first, I thought it was the acrylic lens, but a close examination revealed this was not the case. Is it possible that this chemistry may have very, very diminished lines that 'leak' and in combination, appear white?

Configuration specs:

LM317 current regulator, 6V input, 13.7mA supplied to LD.
PS3 stacked LD, only blu-ray wired and pinned out. Other LD lines left open.
Aixiz standard 12x30mm housing, unmodified acrylic lens.

Additional test operation at 45mA. TEM00 output at <=15mW. No noticeable artifacts in output. Negligible thermal output. Duty cycle 30s:120s
 



Benm

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It is possible for semiconductor sources like lasers and LD to put out different light colors at extremely low currents. This has mostly been demonstrated for powerful blue LEDs, that sometimes glow a dim yellow on low voltages.

The idea is that this is caused by impurities in manufacturing, where some tiny pieces of the junction have lower bandgaps. At proper currents the effects from these are overwhelmed by the desired output.

I guess its possible to reach a point where both the impure regions emit light and some of the closer-to-desired regions also light up, resulting in a mixture that resembles white light.
 

Greyfox

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Thank you for the reply. It makes sense, but I wasn't sure if such a thing was regularly noted on less common lasers. I guess I must have set it just right to have such an unusual find.
 




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