IMAGING LASER-RADAR IN THE NEAR AND FAR-INFRARED

Recent advances in laser transmitter technology have made available to the laser radar system designer a multitude of wave-bands from which to choose, There are four infrared wavebands receiving emphasis for mo dest to long range (1-10 km) imaging applications, each of which conta ins efficient, mature source technologies suitable for commercial or t actical military applications. These wavebands include the far-IR band centered at 10.6 mu m and the near-IR band with three subbands locate d near 2 mu m 1.5 mu m, and 1 mu m. Visible wavelengths are usually av oided for reasons of eye-safety or detectability. The near-IR subbands coincide with the peak spectral responses of the three most suitable photodetector materials in the near-IR band and include a variety of l asing molecules, ions, transitions, and host materials. The most effic ient and mature of these include the CO2 gas laser at 10.59 mu m the H olmium, Thulium solid-state laser(s) near 2 mu m the optical parametri c down converted Neodymium solid-state laser(s) operating near 1.5 mu m, and the Neodymium laser(s) operating near 1 mu m. Diode lasers are not considered due to their low peak power capabilities. A brief compa rative performance analysis is presented for the ground-to-ground scen ario which discusses the key tradeoff issues between the various waveb ands with emphasis on atmospheric effects, including atmospheric turbu lence. A nominal set of system requirements and design parameters are chosen which, when used in the analysis, lend insight into the perform ance trends expected for the various wavebands. Atmospheric propagatio n is modeled using MODTRAN and FASCODS for medium and high resolution spectral absorption profiles, respectively. Example field data is pres ented from the Raytheon Electronic Systems 10.59 pm coherent Tri-Servi ce Laser Radar (TSLR), a Hercules Defense Electronic Systems, Inc. 1.0 64 mu m Neodymium direct detection laser radar and a Fibertek; Inc. 1. 54 mu m OPO:Nd direct detection system.