[Laser] 5 mW lasers & LEDs - Detectors

[Steve J. Noll]

On 11/1/2013 10:39 AM, Zack Widup wrote:
> Once upon a time, probably several years ago, there was some discussion
> about what detector diode device was best for laser reception. I remember
> there was one device in particular that was recommended and that it was
> somewhat difficult to come by.
>
> Things may have changed since then with advancing technology. Are there any
> suggestions?
>
> 73, Zack W9SZ


I'd like to see that discussion too!

I believe one may want to look at it two ways - setups "capable of 
communications at a range of at least 1 km." or setups for balls-out 
record setting distances.

For the latter, really can't beat a photomultiplier tube. Next would be 
an avalanche photodiode.
I just retired from being senior test engineer at Advanced Photonix 
where we made large area Silicon APDs, 5mm to 16mm dia, the biggest in 
the industry.
Unfortunately, they're really expensive, even as surplus, as they're not 
easy to make. Also require ~1800V. As the operating point is temperature 
sensitive they're usually TE cooled.
These were supposed to be a PMT-killer, they haven't been.  They're the 
sensors in the Optos scanners at your better-equipped eye doctor.

Then there's small area APDs. We made those for long-range barcode 
scanners. 100V to 200V.
I see on eBay right now First Sensor (formerly Pacific Silicon Sensor) 
AD500 small area APDs for $16 from China. How someone can sell these for $16
when they're $135 from Mouser is a mystery, one hopes they're not 
rejects. Their spectral response curve is not great. About 155V bias 
requirement which is also temperature dependent.
The biggest disadvantage is the tiny active area (500 um.) Can you get 
most of your receive signal on that 20 mil spot?
If not then I'd go with a regular silicon photodiode which you can get 
with much larger active areas. And they're cheap.

73,
*Steve J. Noll, WA6EJO
http://www.qrz.com/db/WA6EJO
http://www.linkedin.com/in/stevejnoll
*