The Use Of Geiger Mode Avalanche Photodiodes For Precise Laser Ranging At Very Low Light Levels: An Experimental Evaluation

Abstract

Measurements have been conducted to determine the utility of commercially available silicon avalanche photodiodes as detectors in single photon ranging systems. When cooled and operated in a gated Geiger mode these detectors offer an attractive alternative to photomultipliers. Seven different types of diodes were evaluated for Geiger mode operation. Characteristics such as dark noise and temporal response were used to select the best diode types. Response time studies were conducted on the selected diodes at very low light levels using a mode-locked frequency doubled Nd:YAG laser and a picosecond resolution streak camera system. Single photon response time distributions with standard deviations as small as 90 picoseconds were observed. Detection efficiency at the singles level was also studied. Using a parametric down conversion process to generate a source of correlated photon pairs, the absolute single photon detection efficiency was measured at 532 nanometers. Efficiencies of 28% were observed and changes in the detection efficiency with gating voltage were studied. Results from low and moderate intensity laser ranging with Geiger mode diodes are discussed. The ranging results acquired at the Goddard Optical Test Facility include both terrestrial targets and the Laser Geodynamics Satellite, LAGEOS.