Abstract

We have developed an eyesafe lidar system for tropospheric cloud and aerosol studies using the Raman-shifted output from a Nd:YAG laser as the lidar source. The Nd:YAG beam pumps a cell containing methane at high pressure which undergoes stimulated Raman scattering, producing 1.54-μm pulses. The output beam is then expanded to produce an eyesafe beam at the output of the transmitter. The receiver unit consists of a 40-cm Newtonian telescope with a telecompressor to reduce the effective focal length of the telescope. The backscatter return is detected with an In-GaAs photodiode followed with a GaAs FET low noise preamplifier. The preamplifier output is digitized using a 20-MHz transient recorder. The transient recorder output is recorded using an IBM PC-AT computer, which also performs data analysis. To date, we have measured cirrus back scatter from 11-km altitude and aerosol return from ranges of more than 4 km. Measured system performance approximately matches that expected from a system analysis. Our results indicate that this Raman-shifted lidar has the sensitivity to be a useful tool for measurements of aerosols and clouds.

© 1989 Optical Society of America