Amplification of laser echo signal in a turbulent atmosphere

Abstract

Laser beam backscatter in a turbulent atmosphere is analyzed. The mean intensity of radiation scattered in turbulent atmosphere is shown to increase in the backward direction in comparison with the intensity of radiation scattered in the same direction in absence of turbulence, due to the effect of backscatter amplification in random media. As the strength of refractive turbulence increases, the amplification factor first grows, achieves the maximum, and then decreases. The area of manifestation of the backscattering amplification effect in the plane, transverse to the propagation direction, increases in size with intensification of refractive 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 spherical wave and grows with an increase of the inner scale. The data on the amplification effect for the mean power of the lidar echo signal as a function of refractive turbulence strength, regime of diffraction at the transmitting aperture, inner scale of turbulence, and size of the receiving aperture are reported for the first time.