Study On The Generation And Transmission Characteristics Of Multi-ring Vortex Beams

The vortex beam carrying Orbital Angular Momentum has a phase singularity and the wavefront phase is distributed in a spiral structure.In the OAM multiplexing communication system,due to the orthogonality between the OAM modes,the OAM multiplexing can be realized at the same wavelength,which makes it widely used in the fields of information coding,information transmission and data storage.Based on the OAM multiplexing communication system,this paper studies the generation of multi-ring vortex beams and their transmission characteristics in atmospheric turbulence.The main work is as follows:1.The common types of vortex beams are introduced,and taking the typical Laguerre-Gaussian beam as an example,the intensity and phase expressions of double-ring and three-ring vortex beams produced by orthogonal superposition are derived.At the same time,the intensity and phase distribution characteristics of multi-ring vortex beams under different light source parameters are simulated and analyzed,and the variation rules of intensity and phase distribution of multi-ring vortex beams with the topological charge of a single vortex beam are given.2.An experimental platform for generating a double-ring vortex beam using a spatial light modulator was built,and the double-ring vortex beam was generated under the topological charge number of the same sign and different sign.Therefore,the rationality and effectiveness of multi-ring vortex beams are verified.3.Theoretically studied the transmission principle of the double-ring vortex beam,and the stochastic phase screen was used to simulate the atmospheric turbulent medium,and then the change of the light intensity and phase distribution after the double-ring vortex beam was transmitted under different atmospheric turbulence intensity was studied.The results show that the multi-ring vortex beams generated after orthogonal stacking are independent of each other,the inner ring is the one with the smallest absolute value of the topological charge,and the outer ring is the one with the largest absolute value of the topological charge.The greater the difference in the absolute value of the topological load between the rings,the greater the spacing.After the double-ring vortex beam propagates in atmospheric turbulence,its light field is distorted by the influence of atmospheric turbulence,and as the intensity of turbulence increases,the distortion becomes more severe.Since the multi-ring vortex beam carries different OAM,different information can be transmitted at the same time,which can improve the communication capacity and communication coding ability,which is of great significance to the field of communication coding.