[Laser] Re : Drivers?

[f1avyopto at aol.com]

Hi Kurt
Laser diodes have a very low resistance in direct biasing so if you put a fix voltage on the component the over current will kill it immediately.
The driver is use to limit the current near the threshold value that gives the laser effect.
Under the threshold value the laser diode acts like a LED without coherent light.
Over the threshold current value the laser power increases very strongly proportionally to the current.
The fatal damaging current is reached for a very small amount of increasing !
The threshold current is very temperature dependant.
Il is why it is very easy to kill a cold laser diode with the same current that gives the nominal optical power output when the laser diode is hot !
It is why a laser diode includes a feed back photodiode to provide a signal to the driver to stabilise the current for a constant optical output power; 
73
Yves F1AVY
http://f1avyopto.wifeo.com/

 

 


 

 

-----E-mail d'origine-----
De : KD7JYK DM09 <kd7jyk at earthlink.net>
A: Free Space LASER Communications <laser at mailman.qth.net>
Envoyé le : Mardi, 27 Septembre 2011 23:58
Sujet : [Laser] Drivers?


Just getting back into playing with lasers...  It's been twenty years and 
the last ones I played with were tubes.

So, let's say I have a laser module that requires 3.0 volts to operate. 
Most lasers seems to state they  require a constant current rather than 
voltage, why?  I have a power supply that can provide 3.0 volts at more than 
enough amps.  Can't I just connect the module to it direct?  In what 
instances, and for what reasons, are "drivers" used?

Kurt 

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