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

16/08/2011 - 16:04 von Wolfgang.Draxinger | Report spam
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
 

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#1 Dieter Wiedmann
16/08/2011 - 17:08 | Warnen spam
Wolfgang.Draxinger schrieb:

The first unusual thing I noticed was, that those laser diodes had four,
not the usual three connectors.



Das sind wohl welche die zwei Wellenlàngen können, üblicherweise 782nm
und 658nm. In der Regel sind alle drei Kathoden miteinander verbunden
und liegen auch auf dem Gehàuse. Und wenn die Dinger aus einem Brenner
stammen, dann können die ganz schön was an Strom ab.


Gruß Dieter

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