Research On The Axial Scintillation Index Of The Echo Wave In The Slant Path Atmosphere Turbulence

With the development of the laser communications, laser radar and other practical applications, the research on the laser double passage in the atmosphere turbulence has been widely paid attention. The random fluctuation of the refractive index caused by the atmosphere turbulence will lead to the random variation of the optical field of the laser beam, which severely limits the usability of the different laser engineering systems, and even derermine their technical feasibility. Atmospheric scintillation occupies the central position of the light transmission in the atmosphere turbulence. Therefore, this paper discusses the scintillation index of the echo wave in the slant path through the atmosphere turbulence.Firstly, based on the Rytov theory and ABCD transmission matrix method, the logarithmic amplitude covariance function is derived, and the theoretical form of the scintillation index of the echo wave is obtained.Secondly, based on the theory of optical wave propagation in the slant path and the atmosphere refrective index structure constant model which is dependent on altitude, the theoretical model of the echo-wave scintillation index of the incident Gaussian beam is derived considering the inner-and outer-scales, and the theoretical models of the echo-wave scintillation indexes of the incident Gaussin beam, spherical wave and plane wave are deduced considering only the inner scale. The relationship of the scintillation index of the echo wave as the Fresnel rate representing the size of the reflector is derived by using the modified Hill spectrum. The influences of inner scale, the beam’s wavelength and the target height on the echo wave scintillation index are analyzed.