COUNTING, TIMING, AND TRACKING WITH A SINGLE-PHOTON GERMANIUM DETECTOR

We report the performance of a germanium quad-cell, composed of four a valanche photodiodes operated in the photon-counting regime, biased ab ove the breakdown voltage. Each pixel detects a single photon in the w avelength range 1-1.5 mu m with similar to 10% quantum efficiency and measures the photon arrival time with a time resolution of 100 ps. By adopting a multiplexed gating of the avalanche photodiodes we avoided the optical cross talk among pixels, thus achieving a noise-equivalent power of 3 x 10(-15) W/Hz(1/2) for each pixel and demonstrating the t racking capabilities of such a detector. (C) 1996 Optical Society of A merica