Improved CO2 lidar receiver based on ultralow-noise FPA technology

Autor: Dennis K. Remelius, F. David Wells, George E. Busch, David C. Thompson, Phillip L. Jacobson
Rok vydání: 1999
Předmět:
Zdroj: SPIE Proceedings.
ISSN: 0277-786X
DOI: 10.1117/12.366428
Popis: A high sensitivity, CO2 lidar detector, based on recent advances in ultra-low noise, readout integrated circuits(ROIC), is being developed. This detector will combine a high speed, low noise focal plane array (FPA) with a dispersivegrating spectrometer. The spectrometer will filter the large background flux, thereby reducing the limiting backgroundphoton shot noise. In order to achieve the desired low noise levels, the HgCdTe FPA will be cooled to -5OK. High speed,short pulse operation of the lidar system should enable the detector to operate with the order of a few noise electrons in the combined detector/ROIC output. Current receiver design concepts will be presented, along with their expected noise performance.Keywords: LWIR lidar receiver; focal plane array; ultra-low noise ROTC, HgCdTe infrared detector 1. INTRODUCTION The application of CO2 differential absorption lidar (DIAL) to chemical remote sensing allows extremely sensitivedetection of atmospheric constituents. In the DIAL technique', the transmitted laser pulse propagates through the atmosphereto a hard target and the reflected light is collected by a receiver telescope and focused onto a detector. By tuning the laserfrequency over various laser lines, the spectral variation in absorption "fingerprints" existing chemicals along the laser path.A state-of-the-art DIAL system built at Los Alamos National Laboratory (LANL) presently uses a CO2 laser transmitter and asingle element HgCdTe photovoltaic sensor to measure the magnitude of the backscattered laser pulse. The detectionsensitivity of such DIAL systems, although dependent on many experimental factors, may still be significantly improved byadvancing the technology of basic laser and detector components. Development efforts toward improving the detector arepresented in this paper.In a DIAL sensor, the laser wavelength should be tuned rapidly through a set of chosen spectral lines. Withincertain limits, the faster the lines are tuned, the more shots that can be averaged (in a given time) and the S/N of the sensorwill improve. While being rapidly tuned in wavelength with each shot, the laser output must remain stable, both in mode andin energy. At LANL, a recently demonstrated technique2 uses acousto-optic (AO) technology to tune the laser wavelengthand achieves high pulse repetition frequencies (pro on the order of 5-10 kHz, with no moving parts. On each pulse, the AO"tuner" can select a different laser line and a set of wavelengths can be cycled through at a rate of
Databáze: OpenAIRE