Transmission Characteristics Of Partially Coherent Flattened Beam In A Turbulent Atmosphere

In laser materials processing, laser nuclear fusion, laser ranging and laser radar, etc., it often requires flat-topped beams which have intensity of uniformly distributed in space. A lot of theories and experiments show that atmospheric turbulence will change the transmission characteristics of the beams and reduce its qualities.But most of the current studies focused on the beams' intensity distribution impacted by atmospheric turbulence. The research of propagation characters such as spatial coherence and polarization is very little. Therefore, this article focuses on propagation properties of partially coherent flat-topped beams in atmospheric turbulence.This article has conducted the research of propagation properties of partially coherent flat-topped beams in atmospheric turbulence mainly from the fundamental research and simulation. Firstly, the article derives the propagation equation of partially coherent flat-topped beams in atmospheric turbulence based on the model of flat-topped beams that bringed forward by Li. Then analyzed the luminous intensity, the beam width and spectral properties of partially coherent flat-topped beams through the equation. Secondly, based on the extended Huygens-Fresnel principle, the expression for the degree of polarization of partially coherent flat-topped beams in atmospheric turbulence is derived by using the quadratic approximation of Rytov' s phase structure function and the unified theory of coherence and polarization. The properties of the spatial degree of coherence in turbulence atmosphere were investigated numerically in the last.The resultes are of great importance in the areas of laser radar, laser missile-guidance and communication.They also can provide theoretical basis for experiments.