Study On The Method Of Generating Coherent Vortex By Array Laser

The coherent vortex has the characteristics of carrying topological charge information in its correlation dimension,and it is a new information transmission method in the field of optical micromanipulation and optical communication.There is a phase spiral structure in the correlation space of coherent vortices,which is widely used in the field of particle micromanipulation.Compared with optical vortex field,because of its low coherence,it is less affected by atmospheric turbulence and propagation through obstacles,so it is of great practical significance to study the generation method of coherent vortex.Some studies have shown that there is a vortex mixing field in the superposition field of coherent laser beam array,and some scholars have proposed a method to generate a vortex array in the partially coherent beam array.However,according to the existing research results,there is still a gap in the generation of vortex field by modulating the phase and correlation structure of partially coherent array.Because the phase modulation of low coherence array light is difficult,there are few related experimental reports.Based on this,in this paper,we propose an experimental method to generate coherent vortices by adjusting the correlation dimension of partially coherent optical arrays.This generation mechanism can be applied to beams with low coherence.At the same time,the propagation characteristics of partially coherent array beams in free space and atmospheric turbulence are considered.The average intensity distribution and spatial phase distribution of the output field are observed by combining the transmission distance,the correlation length of the light source,the initial phase and other factors,and all these influence factors on the coherent vortex is analyzed.1、This chapter introduces the research background of array laser and the research status at the domestic and abroad in detail,discusses the application and academic research significance of array laser in various optical fields,expounds the basic theory of array laser,and briefly describes the expression formulas of the array light field on the source surface with different arrangement are described.In view of the ability of low coherence partially coherent beams to resist turbulence,partially coherent beams are selected as the basic sub-light source of array beams,and the basic theory and transmission characteristics of partially coherent beams are further introduced.2、Based on the method of beam phase modulation,the phase modulation of the radial Gaussian-Schell mode array beams is carried out in this chapter.The problem of the array beams transmission is calculated by the efficient tensor approach(ETA).The ETA algorithm of the array beams transmission is introduced in this chapter.Then,the effects of the propagation distance and the initial phase parameters on the far-field intensity distribution,the spatial amplitude distribution and the spatial phase distribution are discussed.On this basis,this chapter further calculates the cross-spectral density function of the classical Gaussian-Schell model beam in turbulent propagation conditions,and analyzes the influence of atmospheric turbulence medium on the propagation of partially coherent array beams.3.Based on the beam theory of Gauss-Schell model,the spatial coherence structure of array field is designed.Based on the extended Huygens-Fresnel diffraction integral,the expressions of the cross-spectral density function and the probability function of the orbital angular momentum(OAM)in output vortex field of the radial partially coherent random array lights(PCL)with the initial phase modulated spatially are derived.The intensity fluctuation and spatial coherence of radial partially coherent random array beams in free space are studied under the condition of weak coherent combination.The results show that the array beams with such modulation can not produce the light field with singularity characteristics with the change of distance.4、In this paper,a method of generating coherent vortices by modulating the phase information carried by the cross-spectral density function of the array light source is introduced.The theory of coherent vortex is described,and the experimental optical path of the optical system is built under the support of the existing theory and experimental conditions.In this process,the spatial light modulator plays the hologram calculated by the prog ram to realize PCL array source.Based on the analysis of the intensity distribution and spatial Fourier transform structure of the output field of PCL array source in the mode of independent disturbance and unified disturbance,combined with the Mach-Zehnder interference experiment,it is concluded that coherent vortices can be generated in the case of independent disturbance of PCL array source.