Research On Adaptive Optics Correction Technique Of Vortex Beams

The vortex beam is a kind of beam with phase singularities.Its light intensity distribution is annular and the center is a dark nucleus.The phase distribution structure is spiral and carries Orbital Angular Momentun(OAM).Vortex beams have been applied in many field,such as optical tweezers,particle manipulation,biomedicine,and optical communications.In addition.because OAM has infinite dimensions,and different OAM is mutually orthogonal,multiplexing techniques can be used to implement OAM multiplexing transmission and improve the channel capacity and spectrum efficiency of the optical communication system.Based on this background,in this paper,two kinds of Adaptive Optics(AO)correction techniques without wave-front sensors are investiagted in detail,and vortex beams are Wave-front distortion correction experiments are implemented to vortex beams.The main works of this paper are as follows:1.The transmission characteristics of vortex beams are investigated in atmospheric turbulence.The theoretical model of laser transmission is introduced.The intensity and phase distribution of the Laguerre-Gaussian(LG)beam transmitted through the atmospheric turbulence channel is investiagted by simulation;According to orbital angular momentum spectrum decomposition theory of vortex beam,the characteristics of the topological charge expansion and the orbital angular momentum model purity variation are investiagted.2.Adaptive correction technologys of vortex beams are discussed.Two kinds of self-adaptive optical correction technology without wave-front sensor are investiagted,including GS algorithm and stochastic-parallel-gradient-descent algorithm.The wave-front distortion correction of single-mode and multimode multiplexing vortex beams have been achieved by simulation.3.The wave-front distortion correction experiments of vortex beams are achieved.The wave-front distortion correction effects of single-mode and multimode multiplexing vortex beams are verified by the two adaptive optical correction techniques without wave-front sensors,which proves the correctness and effectiveness of the theoretical algorithm.The researches show that when vortex beams transmit in atmospheric turbulence,the distribution of light intensity and phase distribution will be distorted,the topological charge is extended and the purity of OAM mode decreases with the increase of transmission distance.GS algorithm for single-mode and multimode multiplexing vortex beams can realize effective wave-front aberration correction,SPGD algorithm has good effect for single-mode vortex beam but the correction effect to multimode multiplexing vortex beams is not ideal.