Unexpected behavior of laser diode salvaged from DVD drive(s)

[Wolfgang.Draxinger]

Hi,

my current pet project is a digital optical communications system. For
that, I was given a large bunch of old, identical DVD drives (non
broken) to salvage parts from. So took the DVD drives' laser diodes, of
course with ESD protection.

The first unusual thing I noticed was, that those laser diodes had four,
not the usual three connectors. So I spent some time figuring out (or
so I think) the pinout:

LD_Cathode LD_Anode PD_Anode PD_Cathode

In the end I had the laser diode shining, regulating up the current and
laser operation beginning at around 10mA -- directing it through an
etalon I could see the fringes, as soon as coherent radiation was
emitted.

Since I have a large number of those diodes I decided to sacrifice one
or two to measure their safe operation limits. So I began yanking up the
current, expecting COD or some other form of damage at some point. At
about 100mA it got dimmer, but to my surprise when I reduced the
current back to 10mA it was again emitting bright, coherent radiation
(passing through the etalon fringes well visible). So in "vain" I
yanked up the current up to 500mA, but still no damage on the laser
diode, which isn't what you'd expect.

Any ideas what is going on there?


Wolfgang

 

[Uwe Bonnes]

Hi,

my current pet project is a digital optical communications system. For ....
or two to measure their safe operation limits. So I began yanking up the
current, expecting COD or some other form of damage at some point. At
about 100mA it got dimmer, but to my surprise when I reduced the
current back to 10mA it was again emitting bright, coherent radiation
(passing through the etalon fringes well visible). So in "vain" I
yanked up the current up to 500mA, but still no damage on the laser
diode, which isn't what you'd expect.

Wenn die Dioden warm werden, dann geht die Lichtausbeute deutlich
zurueck. Kann das evt. nicht auch den Effekt bei 500 mA erklaeren?

 

[Wolfgang.Draxinger]

Wenn die Dioden warm werden, dann geht die Lichtausbeute deutlich
zurueck. Kann das evt. nicht auch den Effekt bei 500 mA erklaeren?

Vorher sollten die doch durch COD sterben und danach nur noch als LED
leuchten oder so, wenn überhaupt. Aber da war nach wie vor
Laseraktivität.


Wolfgang

 

[Wolfgang Schmidt]

Am 16.08.2011 19:00, schrieb Uwe Bonnes:

...............
Wenn die Dioden warm werden, dann geht die Lichtausbeute deutlich
zurueck. Kann das evt. nicht auch den Effekt bei 500 mA erklaeren?

Die Lichtausbeute geht nur relativ zur elektrischen Leistung zurück.
Absolut sollte sie weiter steigen, bis zum Exitus.

Wolfgang