Dual-wavelength locking technique for coherent 2-µm differential absorption lidar applications

A dual-wavelength locking technique for coherent 2-µm differential absorption lidar (DIAL) applications has been developed for simultaneously measuring water vapor ( H 2 O ) and radial wind velocity profiles. The two wavelengths for DIAL measurement were stabilized by sidebands of an electro-optic modulated laser, which was locked to the C O 2 R30 absorption line. We selected wavelengths of 2050.550 and 2051.103 nm to minimize the effects of height-dependent temperature and pressure variations. The long-term wavelength stability of the two locked lasers of < 0.2 p m , which corresponds to 14 MHz, was achieved. The DIAL instrument using the developed technique meets the requirement of measuring the H 2 O concentration with a systematic error < 5 % below an altitude of 5 km.