[Laser] Laser diode characteristics.

[laser@mailman.qth.net]

In a message dated 11/3/02 6:46:31 PM GMT Standard Time, n9jim@pacbell.net 
writes:


> David
> There usually is a max rating on the datasheet, but it is usually power 
> based.
> 
> Why not build a crude power meter?
> 
> Take one of your detectors and a pull up bias resistor, (or a solar cell 
> without) and connect to a volt meter. Then use some known (or relatively 
> known) laser to set a reference.
> Then see what happens as you adjust the bias of the diode under test.
> 
> 

Thanks Jim.

The power meter idea is great. I have a couple of Burr Brown OPT101 chips 
which don't have a good enough NEP for serious DX but would be good for a 
power meter.

The data sheets have surprised me by how broad the spec's are.
For the 5mW diodes (from the Vienna (Austria )company)the threshold is 
anywhere from 25 to 45mA.  Mine has measured at 32mA.
The same data sheet says that the operation point for 5mW is from 28 to 48mA.
I've assumed that the extra 3mA equates to going from threshold to full power 
output!

The relationship is a little more complicated for the 20mW diode, but with 
such a small margin, no wonder laser diodes have a reputation for being 
fragile.

Thanks again

David  G0MRF


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