Research On Optimal Control Technology Of Communication Beam Scatter Angle Based On SLM

Free space laser communication is a process of transmitting information in different channels with laser as carrier.In the long distance laser communication system,under the influence of random jitter at the receiving terminal and atmospheric turbulence,the communication beam will drift,expand and flicker,which leads to the decrease of optical power at the receiving terminal,the decrease of communication system performance,and even the interruption of communication in serious cases.The optimal control of the laser beam scattering angle can solve the problem of low receiving light power in the laser communication system.According to the communication condition,the laser beam scattering angle can be adjusted so that the laser can be captured by the receiving terminal as far as possible and improve the performance of the whole communication system.In recent years,laser communication technology has been widely used in aerospace,national defense reconnaissance and other fields.Therefore,in order to improve the overall performance of the communication system,the optimal control of the communication beam scattering angle has gradually become a focus of attention in the field of laser communication.Based on the application background of free-space laser communication system,this paper designs an optimal control scheme of communication beam scatter angle based on liquid crystal spatial light modulator(LC-SLM),conducts theoretical research and simulation analysis on its basic principle and performance,and verifies the performance of the whole scheme through the combination of hardware and software and experimental verification analysis.The specific main work is as follows:1)The principle of traditional control method of laser beam scattering angle is studied theoretically.Firstly,the principle of Gaussian beam lens transformation and the principle of variable beam scattering angle optical system are analyzed.Then the modulation principle of the main optical element LC-SLM beam scattering angle is analyzed,and the minimum focal length of the simulated lens is calculated to be 64 mm according to the relevant parameters.Secondly,the whole idea of laser beam scattering angle control is analyzed,and the appropriate system structure is selected according to the actual technical requirements.Finally,the principle of compensating turbulence wavefront distortion by LC-SLM is analyzed,which lays a foundation for the subsequent construction of beam dispersion angle control experiment system.2)The key scheme verification of laser beam scattering angle optimization control based on LC-SLM was studied theoretically and experimentally.Firstly,the average error of LC-SLM’s simulation varifocus lens is verified within 0.8%.Then,a laser beam scattering angle control system was constructed.LC-SLM was combined with a lens with a focal length of 500 mm to control the incident beam scattering angle,and the RMSE of the beam scattering angle control system was 0.0175.Finally,a compensation system for turbulence wavefront distortion is built.After compensation,PV value of the wavefront decreases from 1.864 λ to 0.132 λ,RMS decreases from 0.213 λ to 0.042 λ,and the wavefront compensation effect is obvious.3)The composite optimal control technique of laser beam scattering angle based on LC-SLM is studied theoretically and experimentally.Firstly,the optimal control system of communication beam scatter angle is constructed.Then,based on LC-SLM,a composite control method of laser beam scattering angle and compensated turbulent wavefront is proposed.Finally,the effectiveness and feasibility of the composite control method are verified and analyzed.The average error of the optimized control system of laser beam scattering angle is less than 8%,and the wavefront aberrations after compensation are less than λ /8,which improves the accuracy of laser beam scattering angle control and meets the expected requirements of the experiment.The research of this paper has important reference value for the laser parameter control technology in the field of free space laser communication.