Abstract

Lidar systems rely on backscattering from air molecules (Rayleigh scattering) and from suspended aerosol particles (Mie scattering) for their return signal. Due to the thermal motion of both molecules and particles the backscattered light is Doppler broadened in frequency. Molecular backscattering has a temperature dependent linewidth of 2 GHz. Aerosol particles, being many orders of magnitude heavier than molecules, show much slower thermal motion and the resulting Doppler broadening can be neglected in most circumstances. The spectrum of backscattered light, consisting of a wide Rayleigh and a narrow Mie scattering component, is shown in Fig. 1(a).

© 1987 Optical Society of America