Time Correlation Analysis Of Laser Beam Atmospheric Transmission Phase Screen Simulation

Laser beams have been widely used as information carriers in atmospheric laser communications.In the simulation analysis and experimental verification of the characteristics of the laser communication link in the atmospheric turbulence environment,the lack of time correlation information will lead to incomplete simulation process and deviation of test results.Therefore,studying atmospheric turbulence simulation technology,and then verifying and analyzing the temporal correlation of turbulence phase screen simulation in laser atmospheric transmission,etc.,is of great significance for improving the working performance of atmospheric laser communication systems.In the laser atmospheric transmission system,a turbulent phase screen is generated by the power spectrum inversion method and Zernike polynomial method,the Liquid Crystal Spatial Light Modulator(LC-SLM)is used as an atmospheric turbulence simulator to load a phase screen to phase-modulate the laser beam.Then,the time correlation of the phase screen simulation is compared and analyzed by measuring the relevant parameters.This paper first discusses the basic theory of laser atmospheric transmission and the turbulence phase screen simulation technology,and proposes a method of rotating the interception phase screen to simulate dynamic time-varying atmospheric turbulence.Experiments are carried out by building a turbulence simulation system based on LC-SLM.It is verified that LC-SLM has the ability to simulate atmospheric turbulence.Then the method of time correlation analysis of phase screen simulation is studied,which lays a theoretical foundation for subsequent research.Finally,a laser-atmosphere transmission phase screen simulation system based on LC-SLM was designed and constructed,and the time correlation parameters of the phase screen simulation were evaluated,namely the Greenwood frequency of atmospheric turbulence and the time power spectrum of irradiance.When the Greenwood frequency is above 64 Hz,the experimental and theoretical values of the turbulence phase screen simulated by power spectrum inversion are close to coincide.The Zernike polynomial method is used to simulate the turbulent phase screen,and the experimental value is close to the theoretical value when the range of Greenwood frequency is above 80 Hz.The irradiance time power spectrum transmitted by the beam in the turbulent phase screen simulated by the power spectrum inversion method is closer to the theoretical value than the Zernike polynomial method.And the two adjacent moments in the time domain waveform of the beam transmission are related,and the normalized gradient between the neighboring moments is 0.1(25)0.8.The power spectrum inversion method is more compact and continuous than the Zernike polynomial method to simulate the adjacent moments of the turbulent phase screen,that is,the turbulence phase screen simulated by the power spectrum inversion method is more relevant in time.The experimental analysis results show that the power spectrum inversion method is better thanthe Zernike polynomial method to simulate the time correlation of the phase screen.The work done in this paper provides a theoretical basis and experimental basis for verifying and analyzing the time correlation of the laser atmospheric transmission phase screen simulation,and provides a new idea for evaluating the simulation accuracy of turbulent phase screen.