Detector performance studies for CO2 laser heterodyne systems

The authors discuss experimental results obtained with Joule-Thomson cooled CMT photodiodes, in a variety of systems and applications. Two types of study have been conducted, firstly an evaluation of a range of detectors on the laboratory bench, and secondly, performance studies on detectors installed in different lidar equipments. It is concluded that a heterodyne detector/amplifier should have the following characteristics: wide bandwidth with flat response; high quantum efficiency over the range of operational frequencies and power levels; well matched bias supply and amplifier; be physically robust, with a long stable life; and reproducible technology