Abstract

Time-correlated single photon counting (TCSPC) is now the procedure of choice for many applications that depend on the detection of low level and/or fast optical signals. For example, use of photon counting in picosecond time-resolved photoluminescence (TRPL) measurements on semiconductor material and devices has led to the study of carrier dynamics at low photo-generated carrier densities (e.g. <10^l5cm^-3) [1]. Also, quantum cryptography [2], which enables the secure distribution of cryptographic keys across telecommunication networks relies on sending the key at the photon per bit level (or less on average). These systems require detectors to possess picosecond time resolution and high detection efficiency. As a consequence, single photon avalanche diodes (SPAD’s) are now widely used for single photon detection in place of photomultiplier tubes at wavelengths below 1µm. A SPAD is a reversed biased diode operated at fields above breakdown, such that a single carrier can initiate a self-sustaining avalanche. Silicon SPAD’s are now commercially available with good room temperature performance at wavelengths below 1.1 µm.

© 1998 IEEE