Control Of Vortex Optical Field Based On 4f System

A vortex beam is a special beam of light with zero central light intensity and a spiral-like distribution of wavefronts.The vortex beam is propagated around the central axis,and each photon carries the orbital angular momentum of lη,which makes the vortex light widely studied in the fields of optical manipulation,optical communication,and quantum communication.With the continuous study of vortex light,more and more methods are used to generate vortex beams,and methods for detecting topological charges have also emerged.As one of the most widely used optical information processing systems,4f optical filtering system also plays a good role in the generation and detection of vortex light.Based on the 4f optical filtering system,this paper analyzes the light field regulation of the vortex beam by loading different filters,and explores the application of shaping based on the 4f optical filtering system in generating high-order Laguerre-Gauss beams and detecting the topological charge number of the vortex beam.The main work of this paper is as follows:1.The regulation of the vortex beam by the loaded triangular hole in the 4f optical filtering system is analyzed theoretically,and the light field distribution on the image plane after the vortex beam of topological charge l???(28)3,2,1 passes through the system.The results show that according to the distribution of the light field on the image surface can judge the topological charge of the incident vortex beam.The light field on the image surface is distributed in a triangular lattice,and the topological charge of the incident vortex beam is related to the number of light spots on the outermost side of the triangular plexus,while the positive or negative of the topological charge of the incident vortex beam is related to the vertex direction of the triangular lattice,and the influence of the loaded triangular aperture size on the light field distribution on the image surface is discussed.2.Theoretical analysis is carried out to filter and shape the vortex beam by loading the ring filter on the spectral plane of the 4f optical filter system.The light field distribution on the image plane of the Laguerre-Gaussian beam with different topological charges and zero order radial index is simulated and analyzed after passing through the 4f optical system loaded with a ring filter.The research shows that the ring filter can shape the zero-order radial-index Laguerre-Gaussian beam into a high-order radial-index Laguerre-Gaussian beam,and the effect of the ring geometry on its vortex beam shaping is discussed.Loading a ring filter with a 4f optical filter system provides a very efficient scheme for generating high-order Laguerre-Gaussian beams.3.The regulation of the vortex beam by the loading phase-type spiral zone plane in the 4f optical filtering system is analyzed theoretically,and the light field distribution after the eddy beam regulation of different topological charges is analyzed numerically in the 4f system.The results show that when the topological charge of the spiral zone plate is m(28)1,the topological charge of the input vortex beam can be judged according to the light intensity distribution on the imaging plane.However,when the spiral zone plate loaded with a topological charge of m(28)2(or >2)filters the vortex light,the degree of "destruction" of the light field on the image surface will become larger,showing irregularity,which cannot be based on the image surface.The light field information determines the topological charge of the incident vortex beam.Selecting an appropriate phase-type spiral zone plate to filter the vortex beam can provide a novel method for topological charge detection of the vortex beam.