High Speed Room Temperature Single Photon Counters

Detecting light at the single photon level is a fundamental measurement function that is useful in a wide variety of applications, including such diverse fields as biological spectroscopy, laser ranging, and quantum communications. Avalanche photodiode (APD) based single photon detectors (SPDs) are very convenient in that they are small solid state devices that don"t require cryogenic cooling. Si-based APD devices have high performance for<1 micron wavelengths. III-V material APDs are sensitive to the telecom bands (1.3 and 1.5 micron), but generally have inferior performance. Recently methods of high speed gating of III-V APDs has lead to dramatic improvements in their speed. We propose to optimize the III-V APD performance for high speed (GHz) gated operation by appropriate electronic control and system optimization. The use of nonlinear frequency conversion can allow for higher performance Si detectors to measure telecom wave-bands. The nonlinear interaction can add extra noise however. We will build a model for the noise processes and validate it with experimental measurements. The high speed performance of the Si detector will also be optimized. The feasibility of combining appropriate up-conversion with such high speed Si APDs for building low-noise multi-GHz detectors will be evaluated.