Spectral diversity technique for heterodyne Doppler lidar that uses hard target returns

A two-mode CO, laser is used as transmitter in a 10-mu m heterodyne Doppler lidar (HDL) to take advantage of a spectral diversity technique, i.e., ind ependent realizations obtained with different spectral components. The obje ctive is to improve the properties (i.e., less variancefofpower returns fro m a hard target. The statistical properties are presented first for a broad -spectrum laser transmitter and then for a two-mode laser transmitter. The experimental results for a cooperative diffuse hard target show that the re turn signals for a frequency separation Delta f = 15 MHz can be decorrelate d, depending on the angle of incidence and the target roughness. The experi mental results show that the spectral diversity technique improves the perf ormance of the HDL. (C) 2000 Optical Society of America OCIS codes: 010.364 0, 030.6140, 040.2840, 280.1910, 290.5880.