Frequency Agile Lidar Receiver for Chem-Bio Sensing

Abstract : Physical Sciences Inc. (PSI), in conjunction with its subcontractor, VTech Engineering Corp., developed an ultra low noise receiver module (RM) for direct detection LWIR LIDAR systems. The receiver module is compatible with emerging LWIR source technologies, e.g., optical parametric amplifier-based sources, as well as existing frequency-agile CO2 laser technology. In this paper we present RM performance attributes based on characterization experiments performed in the laboratory, as well as part of the system integration in the ECBC's Frequency Agile LIDAR (FAL) unit. The RM has been demonstrated to be compatible with a 200 Hz shot-to-shot line tuned CO2 laser in terms of both tuning speed and wavelength accuracy. The system achieves tuning times of less than 5 msec for wavenumber jumps <= 10 cm-1 and transmission measurement errors of ~0.5% due to etalon absolute positioning uncertainty. The system has been demonstrated to achieve a total Noise Equivalent Power (NEP) of ~ 1.7 nW for an electronic bandwidth of 5 MHz when observing a background of Tbkgd = 400K. This represents ~40% improvement over an equivalent detector/preamplifier configuration without PSI's tunable etalon technology.