Abstract

One potential approach to monitoring atmospheric pollutants is the use of differential absorption lidar (DIAL). In this technique two laser pulses are transmitted: one laser pulse on a resonant absorption of the species being monitored and the other off resonance. The CO₂ TEA laser has been successfully used to obtain path-averaged concentration measurements using a retroreflector or a topographical target¹. The usefulness of this technique would be greatly increased by using a distributed scatterer such as the naturally occurring atmospheric aerosols. A CO₂ TEA laser can provide sufficient peak power to perform this task; however data collection is limited by the low PRF's (1-100Hz) available. A possible alternative is a low pressure Q-switched CO₂ laser in conjunction with a heterodyne receiver such as is currently being used for existing CO₂ laser radar systems². Heterodyne detection lowers the required transmitter power while the high PRF (20-50kHz) of a Q-switched laser reduces the data collection time. Such a system designed for DIAL operation could provide range-resolved blanket area coverage with high up-date rates (~1 per min.).

© 1983 Optical Society of America