[Laser] APD diodes in Geiger mode

[Tim Toast]

While looking up some info, i was surprised to see
that APD's don't outperform regular PIN diodes for low
bandwidth applications. (i assume thats comparing both
diodes cooled to the same temperature) It seems odd
that something so sensitive as to pick out individual
photons could also suffer from an excess noise to the
point that it fails to outperform a device it's
supposed to be 1000 times better than. But the
universe is stranger than we can imagine i suppose :)

Here's an excerpt from that first page link down
below:

"Even though an APD gives an amplified output, its
signal-to-noise performance (SNR) is not necessarily
better than that of conventional photodiodes, as APDs
suffer from more shot noise (random fluctuations in
the current flow). This is a consequence of the excess
noise factor, which does not appear when regular
photodiodes are used. In practical systems the SNR
tends to be improved in higher bandwidth applications
by use of an APD over a conventional photodiode,
whereas in lower speed applications use a low noise
photodiode with a high performance op-amp, generally
gives superior SNR."

http://optics.org/optics/Articles.do?channel=technology&type=ole&volume=10&issue=11&article=4&page=1

some other links that looked infoy:
http://optoelectronics.perkinelmer.com/content/whitepapers/AvalanchePhotodiodes.pdf
http://xqp.physik.uni-muenchen.de/publ/echodiode.ps
http://www.iet.ntnu.no/groups/optics/qcr/torbjoern/
http://www.sensl.com/pdfs/jackson_spie_4650_7_02.pdf



Tim Toast
http://www.aladal.net/toast/exp.html

__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com