Non-Gaussian Statistics Of Partially Coherent Light In Atmospheric Turbulence

Laser technology has been widely used in various fields of human production and life.Recently,free-space laser communication technology has been the research spot in the field of laser application.It has been confirmed by a large number of theoretical and experimental studies that the atmospheric turbulence has a serious impact on the efficiency of laser communication.The introduction of partially coherent beams will reduce the negative effects caused by turbulence.the intensity scintillation and beam wander of the beam can be significantly reduced,which makes communication efficiency higher.In this thesis,the basic theory of partially coherent beams,the atmospheric turbulence and the classic model of atmospheric turbulence,laser transmission and its transmission in atmospheric turbulence was introduced first.Then the statistical characteristics of partially coherent beams in atmospheric turbulence with emphasis on fourth-order statistical characteristics was investigated in detail.In Chapter 1,the researches of traditional partially coherent beams and the theory of atmospheric turbulence,as well as the research progress of the transmission of partially coherent beams in atmospheric turbulence are briefly introduced.In Chapter 2,the basic theory which has intimate relation with our investigation was introduced.The first part is about coherence,including spatial and temporal coherence,and then the partially coherent beam transmission.Finally,the statistical characteristics of partially coherent beams in atmospheric turbulence and the negative effects caused by turbulent atmosphere,such as propagation factor,beam wander and scintillation,are also been illustrated.In Chapter 3,based on the approximate theory of weak turbulence,a concise expression of the statistical correlation of light intensity for a partially coherent light beam propagating in atmospheric turbulence in the fast detection volume domain has been derived and it has been verified by experiment.This expression reveals that the correlation characteristic caused by turbulent disturbance only affects the correlation characteristic of partially coherent light intensity as a linear enhancement factor:generally speaking,the maximum value of the correlation of partially coherent light intensity is enhanced by the influence of turbulence,making statistics changed from gaussian statistics to super-gaussian statistics.On the other hand,the expression also reveals that in the case where the beam coherence is sufficiently small,the influence of the turbulence disturbance on the light intensity correlation of the beam itself can be ignored.As a result,the correlation imaging in atmosphere can not be affected by turbulence.In Chapter 4,the main points of the thesis are summarized and the directions for further research in the future are prospected.