in one my of low light pulse detection project i want to sense a very low light of 1mW/m2 so for this kind of scenario an APD is a device with its internal gain can give me abundant current to detect the signal

here is the APD i have choosen

the APD spec does not show any recovery time from saturation, when i asked the manufacturer he said "the recovery time is few uS and its more dependent on the TIA design "

how does an APD recovery time from saturation is dependent on TIA design ?

  • The data sheet covers 3 different detectors. Also, if you are in contact with the manufacturer ask them what they mean. – Andy aka May 27 '16 at 9:34

Possibly because of quenching, depending on where in its response curve you're using it? They're hard beasts to tame, it might be worth looking into silicon photomultpliers (SiPM's) aka SPADs (Single Photon Avalanche Diodes) which have in-built quenching generally and work on lower bias voltages -they also have higher responsivity (in the MA/W range rather than tens or hundreds, of A/W).

I've been evaluating some roughly $90 per piece SiPMs for the last couple of weeks that respond to light pulses in the 1-5µs range that act pretty much like PIN diodes if you give them a -30V bias, but have the sensitivity of a top end PMT at least for wavelengths <700nm.

  • i have read about SPADs but wont they saturate very quickly, equally they are also bulky, will they come in TO packages ?, my requirement is rise time of atleast 2ns and wavelength range of 800-1200 nm, thanks for info, but i need an answer which speaks on APD deadtime dependance on TIA – kakeh May 28 '16 at 2:41
  • @kakeh: Yes, they saturate quickly, since about 1 photon per cell is enough to trigger them. They're really made for few-photo scenarios. I worked on SiPMs of ~1000 cells on a 1mm² die, so no, they're not always bulky. – sweber Jun 2 at 21:41

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