Amplification of laser echo signal in the turbulent atmosphere

Abstract

The distribution of mean intensity of a laser beam backscattered from a remote aerosol layer in the radiation plane is calculated as a function of the intensity of turbulent fluctuations of the refractive index of air at the propagation path. The mean intensity of backscattered radiation is shown to increase in the backward direction in comparison with the case of scattering in a homogeneous medium due to the effect of backscattering amplification in random media. As the intensity of optical turbulence increases, the amplification factor first grows, achieves the maximum level, and then decreases. The zone of manifestation of the backscattering amplification effect in the receiving plane increases in size with intensification of optical turbulence. It is found that the amplification factor depends on the inner scale of turbulence and the regime of diffraction of optical radiation at the transmitting aperture. It is maximal for the regime of spherical wave and grows with an increase of the inner scale. The calculated data on the amplification effect of mean power of the lidar echo signal as a function of optical turbulence intensity, regime of diffraction at the transmitting aperture, inner scale of turbulence, and size of the receiving aperture are reported for the first time.