Utilization of pulsed GaAs diode lasers to complex lidar remote sensing

Abstract

Summary form only given. New aspects of application of pulsed GaAs diode lasers, concerning absorption spectroscopy of water vapour of 8990-9012 /spl Aring/, and Mie-scattering lidar signal in the tropospheric range are reported. Prospective atmospheric monitoring is accessible by the power characteristics of a system utilizing two types of the powerful GaAs diode lasers. Employing optimal photodetection based on computer operated boxcar, data on atmospheric aerosol backscatter signal acquired by DL lidar are presented with relevance to the potential of complex atmospheric remote sensing. These lasers, operated in the pulse-periodical mode with corresponding duty factor, utilize a simple and efficient method of pulsed frequency modulation (PFM), of large modulation range containing a large portion of the analyzed spectrum. They are shown to be feasible for DIAL monitoring of atmospheric humidity, with their radiation matching water vapour spectrum of absorption-coefficients of 0.5-5 km/sup -1/ in Beer's law. The observed spectrum is assigned as rovibrational excitation of third oscillatory molecular overtone of water vapour by cross-reference identification with the theoretical and solar spectrum. A mobile lidar employing powerful pulsed GaAs diode lasers of the near infrared region is constructed. It is designed for diode lasers of broad radiation line. A mathematical filter was developed for optimal noise suppression, analyzing the spectrum of the lidar signal and widening the area of application. Aerosol profiles, hard targets and cloud strata up to a 15 km range in open atmosphere were derived, confirming the efficiency and high sensitivity of the lidar system. Control of emissions of industrial gas pollutants and petrol products by the molecular absorption of methane, and prognostics of potentially hazardous zones in gas transport tubes initiate the goals of further development.