Study Of Atmospheric Turbulence Simulator Using Fractal Method

When propagating in the atmosphere, for the effects of turbulence fluctuation, wave amplitude and phase changing conducted a series of turbulent wave-front distortion effect. Laser beam quality will be inevitably deteriorated by the turbulence effects, hence theoretical research of turbulence effects on laser propagation is of great importance in wide areas of laser application.Besides traditional methods such as experiments and theoretical analysis, numerical simulation is also an effective method to study atmospheric turbulence. Based on the classical Kolmogorov statistical turbulence theory, a fractal model is introduced and used to model the atmospheric turbulence phase screen. And the two different cycle random midpoint motion (RMM) algorithm is used to simulate the atmospheric turbulence phase screen. The simulation results complying with Kolmogorov atmospheric turbulence are obtained by analyzing the simulation results and theoretical ones of phase structure function. The simulation accuracy of the first loop is higher than the second one. However, phase distribution of turbulence phase screen based on the first one is not smooth, there is transition between different points. Performance of atmospheric turbulence phase screen simulation based on the second cycle is also analyzed. The conclusion are following:Atmospheric turbulence phase screen simulation base on fractal method is consistent with the theoretical ones in statistical properties. The simulation error of phase screen increases due to the increasing of fractal iterations from the area of low-frequency to the one of high-frequency; With the increasing grid numbers of phase screen, the accuracy phase screen simulation is reduced. At the same time, the number of phase screen needed is increased; As the number of phase screens increases, the simulation accuracy of atmospheric turbulence phase screens with different intensity is similar.Because of the random midpoint displacement algorithm, the correlation between the phase value of a new growth point and the known points is not guaranteed. This paper presents the improved corrected variance successive random additions (CSRA) algorithm for the simulation of atmospheric turbulence phase screen.In order to simulate the dynamic atmospheric turbulence simulation system, the paper describes a method of covariance generating infinitely long turbulent phase screen. Atmospheric turbulence phase screen is generated by Random midpoint displacement algorithm. Finally, the paper introduces the optical characteristics of the liquid crystal spatial light modulator and the phase modulation principle. Static and dynamic atmospheric turbulence phase screen software control interface implements by C++language, atmospheric turbulence simulator system by liquid crystal spatial phase modulation techniques is constructed to meet laser atmospheric transmission channel in the laboratory experiments.