[Laser] Re : Re : Drivers?

[f1avyopto at aol.com]

Hello Tom
You're right but on many laser diodes the slope of this curve is steeper.
Typically for a small laser diode I threshold 20 mA for I max 40 mA when the diode is cold.
If the diode is hot I threshold becomes 30 mA for I max 40 mA
So the useful variation for a linear modulation is only 10 mA for 40 mA of current max.
A small peak to 50 mA can kill the diode...
But of course with more powerful diodes, the gap is wider and the driver can be less critical
http://www.fiberoptics4sale.com/wordpress/wp-content/uploads/2010/12/image61.png
73
Yves F1AVY
http://f1avyopto.wifeo.com/


 

 


 

 

-----E-mail d'origine-----
De : Tom Becker <GTBecker at RighTime.com>
A: Free Space LASER Communications <laser at mailman.qth.net>
Envoyé le : Mercredi, 28 Septembre 2011 13:52
Sujet : Re: [Laser] Re :  Drivers?


 > ... The driver is use to limit the current near the threshold value 
that gives the laser effect...

Don't you mean Icw, not Ith, Yves?  In the devices I've worked with 
there is a substantial range between Ith (the threshold where the device 
begins to lase) and Icw (the maximum safe continuous current) that can 
be AM modulated.  You'll see the knee at Ith often in literature.  It's 
in the lower-left here: http://repairfaq.cis.upenn.edu/sam/tbldmod1.gif

Tom
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