Abstract

A dual-CO₂ TEA laser DIAL lidar system, entitled ADEDIS has been constructed and used for range-resolved mapping of chemical plumes. The system has detected chemical species such as tri-ethyl-phosphate (TEP) at ranges of 1-2 km with a range resolution of 25 meters at concentrations of 2 mg/m*3. The high-range-resolution capability of the system is achieved through the use of plasma shutter pulse clippers, which extinguish the nitrogen tail of the TEA laser output. ADEDIS employs a servomotor programmable scanner, which allows high-speed accurate scanning over wide fields. Additionally, arbitrary scan patterns can be programmed to allow selected feature if useful, for example, if correlation studies of the Lidar data vs point sensors placed at a finite number of locations are being performed. A large aperture (45.7 cm diameter) f/2.5 receiver telescope in the Dall-Kirkham configuration is used, with an f/0.5 ZnSe field lens to achieve a field-of- view of 5 mrad for the system. A 2 mm diameter HgCdTe photovoltaic detector is used in reverse-bias mode in order to obtain sufficient detection bandwidth (>8 MHz) to resolve the clipped laser pulses. A microvax computer with a programmable 10 bit, 100 MHz digitizer acquires the data.

© 1993 Optical Society of America