Experimental Research On Correction Of Distorted Wavefront By Dual Wavefront Corrector

Due to its fast transmission speed and effective anti-electromagnetic interference characteristics,free-space coherent optical communication has been paid more and more attention in wireless communication.Free-space optical communication transmits optical signals in atmospheric channels.Due to the existence of turbulence in the atmosphere,the optical signal will be randomly interfered and distorted,such as beam drift,phase fluctuation,etc.,thus greatly reducing the performance of communication.In this context,Adaptive Optics(AO)technology has attracted widespread attention because it can well overcome the signal light distortion caused by atmospheric turbulence,so it has been applied in free-space optical communication.This topic mainly studies the correction ability of the AO system based on the dual liquid crystal spatial light modulator structure and the AO system based on the deformable mirror-liquid crystal spatial light modulator structure for the distortion wavefront.The main work of this paper is as follows:1.Numerical simulation of atmospheric turbulence is carried out based on the Hill spectral model,and the distorted spot images of Gaussian beams passing through different turbulent environments are simulated and analyzed;the basic working principle and composition of the wavefront-free AO system are expounded,and the working principle of the Deformable Mirror(DM)and Liquid Crystal Spatial Light Modulator(LC-SLM)are introduced respectively.The evaluation index to evaluate the correction effect of AO system is given.2.The design models of the adaptive optics system based on the dual liquid crystal spatial light modulator structure and the adaptive optics system based on the deformable mirror-liquid crystal spatial light modulator structure are given.The phase modulation characteristics of LCSLM are studied,and the basic theory of phase modulation is discussed in detail.On this basis,the LC-SLM is calibrated with different wavelengths of incident light.According to the derivation process of DM eigenmodes,the response matrix and eigenmodes of the 69-unit DM used in the experiment were measured.Numerical simulations are carried out for the two models respectively.3.The static and dynamic experimental optical paths are built respectively to verify the effect of the system in practical application.When performing static experiments,the LC-SLM has the ability to modulate the phase,enabling it to simulate different turbulent environments.Among them,the static experimental results showed that the structure of the dual liquid crystal spatial light modulator can increase the Strehl ratio of the system from 0.13,0.35,and 0.53 to 0.54,0.74,and 0.91,respectively;the deformable mirror-liquid crystal spatial light modulator structure can increase the Strehl ratio of the system from 0.23,0.26,0.41,0.47 to 0.71,0.75,0.76,0.79,respectively.The results of this paper show that the adaptive optics system based on the dual liquid crystal spatial light modulator structure and the adaptive optics system based on the deformable mirrorliquid crystal spatial light modulator structure can effectively correct the wavefront distortion caused by atmospheric turbulence in free-space optical communication,and the effect is obvious in practical applications.