Research On The Generation Of Speckle Vortex Array And Vector Field Array Based On The Control Of Light Field By Multihole Screen

In nature,random surfaces can be seen everywhere,and coherent light waves will form a random light field after being scattered by a random medium or random surface.Since the advent of the laser,the research on speckle phenomenon has been more in-depth and comprehensive,such as the phase singularity of speckles with different shapes of apertures,and cluster speckles generated by optical diffraction screen modulation.Optical vortices in speckles are complex,diverse and representative.It has been thirty years since the birth of the optical vortex,and research on its properties,generation methods,and applications has made rapid progress.Because it carries different orbital angular momentum,it has been used in optical micro-control,quantum entanglement,information transmission and many other fields,so the generation of vortex arrays composed of multiple vortex light carrying a single or different topological charge has received widespread attention.The use of a spatial light modulator can generate a vortex array light field,which will have greater value in the fields of capturing and observing multiple particles,achieving multi-channel optical fiber communication,and measuring object displacement.Therefore,the study of vortex arrays in speckles and a simpler and more efficient method of generating vortex arrays are more worth looking forward to.Vector light field refers to the light field with different polarization states at different positions in front of the same wave.It is because of its multiple polarization distribution that it has been widely used in many fields.The vector field has developed from the single linear polarization state to the hybrid polarization vector field including linear polarization,circular polarization and elliptical polarization in the cylindrical coordinate system.Using the Poincare sphere as a tool to characterize the polarization state,new vector fields including full Poincaré vector light fields,higher-order Poincaré spheres,hybrid Poincaré spheres and generalized Poincaré spheres have been designed.With the in-depth study of vector light field,the generation of vector light field arrays with multiple singularities with different numbers and positions in the same light field has been favored by researchers,which has enriched the application of vector light field to a certain extent.In this dissertation,based on the control of the light field by a porous diffraction screen,the generation of vortex arrays and optical lattices in cluster speckles is realized,and a six-hole screen structure distributed on the helix is designed to realize multiple types of optical lattices on the Fresnel diffraction surface.The aperture screen light field interference and the quasi-periodic Moire superlattice principle are used to design the aperture screen distribution structure to realize the superposition of left-right circularly polarized light with reverse topological load to generate a vector light field array with rich shapes.The research contents of this thesis are as follows:Chapter 1:We first outline the basic theory of random speckles and the research progress of cluster speckles,and briefly introduce the optical singularities in speckles.Then,the basic concepts and theoretical descriptions of the vortex light field are given.During the thirty years of development of the vortex light field,the research progress at home and abroad is reviewed in accordance with the basic theory,application development,and technological breakthroughs.The important applications in various fields are summarized,and the current generation methods of vortex arrays are introduced and analyzed in detail.Finally,several expressions describing the polarization state of the vector light field are introduced,and the research progress of the vector light beam is reviewed.In particular,the generation method of the vector light field array is introduced in detail.Chapter 2:We present a method for generating optical lattices and vortex arrays using a porous scattering screen.Firstly,cluster speckles were generated experimentally by irradiating a porous scattering screen distributed along the circumference with coherent light,and it was found that the optical lattices contained different primitive structures,such as typical hexagonal lattice with first-order vortex,Kagome lattice with second-order vortex and honeycomb lattice with binarization phase,etc.At the same time,an asymmetric elementary optical lattice formed by 2? non-integer multiple phase modulation was also observed for the first time.The cluster speckle field theory and calculation analysis show that the generation of the optical lattice in the observation plane results from the phase modulation of therandom scattering screen,and the type of the lattice depends on the sum of the phase differences between the holes being a multiple of 2?.In addition,we give the conditions needed to obtain a periodic optical lattice and vortex array.Chapter3: We propose a method to generate multiple optical lattice arrays simultaneously by irradiating the six holes evenly distributed on the helix with coherent light.According to the phase change caused by the distance difference between the spiral hole screen and the image surface,the cluster optical lattice appears at different points on the Fresnel diffraction surface.The existence of vortex array is verified by phase diagram analysis.The effect of three factors on light field regulation is verified by numerical simulation analysis.Firstly,by changing the opening value of helix,the distance from six holes to the center of the observation surface can be changed,so that the light field lattice at the center can be adjusted,and the phase vortex changes with the distance away from the center,and the radial evolution law can be seen from the light intensity.Secondly,the aperture size controls the generation of interference phenomenon;thirdly,the change in the angle of the optical lattice distribution on the image plane is consistent with the change in the arrangement angle of the six holes on the helix.Finally,the density of the optical lattice on the observation plane is affected by the shape of the helix.The larger,the denser the distribution of the optical lattice.The spiral six-hole screen controls the light field to generate a polymorphic optical lattice,which provides a more convenient and effective way for the application of vortex arrays in various fields.Chapter 4: A new vector beam array generation method is proposed by designing two sets of six-hole diffraction screens based on the basic theory of general vector light field generation.Using two sets of aperture screens,the left-handed circular grid light field and the right-handed circular grid light field are superimposed on the Fourier plane to generate a vector light field array.First,a theoretical study is made of the left-right circularly polarized light with opposite orbital angular momentum to irradiate two sets of six-hole screens with the same azimuth arrangement and the same size to generate a periodic vector beam on the Fourier plane.We simulated and verified the generation of the hexagonal lattice vector light field and the kagome vector light field.Next,we discuss the quasi-periodic Mohr superlattice principle based on graphene rotation for the kagome and honeycomb lattices,and change theorientation of the two sets of aperture screens to obtain a new type of light field.The design makes one set of aperture screens rotate 27.796 degrees or 32.204 degrees around the center of the distributed circle,and the other set of aperture screens remains unchanged.Two sets of new aperture screens were irradiated with left-right circularly polarized light with reverse orbital angular momentum and superimposed on the Fourier plane.The state of polarization in the vector beam array is the polarization state of a point on a high-order Poincaré sphere or a generalized Poincaré sphere.This result verifies the conclusion that the multi-hole screen can realize multiple types of vector beam arrays,and the method can adjust the polarization state of the light field by changing the phase distribution of the incident light.This new type of light field structure generated by the multi-beam interference light field formed by the aperture screen brings new application values in topological photonics,spin and chirped spin operations,and topological insulators.Chapter 5:We conclude the work and the achievement of our researches in this paper,and briefly introduce the preconceived work in future.