| Since vortex and helix beams became known,a number of advances have been made in the study of their properties and generation methods,with applications related to their special properties in areas such as particle manipulation,super-resolution microscopic imaging,anomalous topological phasing,and bioscience.As research continues,arrays of vortex and helix optical fields consisting of multiple single beams are receiving attention from researchers.Array-distributed vortex and helix optical fields with multiple phase singularities and multimode orbital angular momentum have important applications in areas such as multi-particle capture,multi-channel communication,optical metrology,and materials processing,which depend on high-quality and specifically distributed array optical fields to be realized.The existing methods for generating array vortex and helix optical fields have drawbacks such as complicated steps,low energy efficiency and small applicability range.Binary optical element is a kind of optical element with periodic distribution of step-like structure,and its energy efficiency increases with the increase of the number of steps,and the theoretical value of energy efficiency of high-order binary optical element is up to 100%.In addition,binary optical elements also have high design freedom and good dispersion performance.With the help of microfabrication process,binary optical elements can be miniaturized and miniaturized to meet the requirements for the integration of optical systems.Based on this,this thesis proposes a method for generating orthorhombic array vortex and helix optical fields using binary optical elements by designing a binary diffraction plate with a special period to achieve modulation of the phase or amplitude information of the optical field,which in turn generates the desired array optical field.The binary diffraction plate can be fabricated by micromachining techniques,and the corresponding experimental optical path is a4 f system,which is simple,stable and easy to build,which provides a fast and efficient method to generate array vortex and helix optical fields.The main research contents of the thesis are as follows:1.The first chapter introduces the research background and significance of this thesis.Firstly,a brief overview of the development,characteristics and application fields of binary optical elements is given,followed by the development history,research status and application scope of vortex and helix beams,and finally an overview of the existing methods for generating array vortex and helix optical fields is given,with emphasis on the existing methods for generating array optical fields using interferometry.2.Chapter 2 is the theory and numerical calculation of multi-beam interference.Firstly,the basic theory of interference is introduced;then the basic theory of two-beam and multi-beam interference is outlined;then the intensity and phase distribution of the interferometric field are given by numerical calculations for three-beam,four-beam,five-beam and six-beam interference,respectively;finally,the theoretical derivation of the common-source multi-beam is presented.3.Chapter 3 presents a method for generating orthogonal array vortex and helix optical fields using a binary phase plate.Here,a periodic orthogonal binary phase plate is designed with periodically distributed rectangular phase modulation cells,and the phase modulation amount of each cell is 0 or π.The spatial spectrum of this phase plate has a central direct component of zero,and the four primary spectral points and eight secondary spectral points in the central region of this spectrum are phase-modulated respectively to generate square array spots and square array vortices.The topological charge l=±1 of each vortex beam in the array vortex is staggered in space.Since the transverse periods of the two square array optical fields in the vertical propagation direction coincide,and the wave vector components of the two optical fields along the optical axis direction are different,the superposition can form a square array helix whose intensity distribution rotates with the transmission distance,and there are two helix beams with opposite helix directions in the array,which are also interleaved in space.In this chapter,the phase plate design conditions for generating the optimal helix beam are discussed and the energy utilization of the system in the ideal case is given.The experimental results verify the feasibility of the method.4.Chapter 4 proposes a method for generating a square array of vortex and helix optical fields using a periodic orthogonal amplitude filter.The amplitude plate is composed of periodic rectangular amplitude modulation units,and the amplitude modulation amounts of adjacent units are 0 and 1.The central direct component of its spectrum is constant,and by spatial filtering and phase modulation of the spectrum,the square array spot and square array vortex optical fields generated by the four spectral components located in the outer layer of the central direct component and the eight spectral components in the second outer layer can be obtained,respectively.the phase difference of adjacent spots in the array spot is π,and the neighboring vortex beams in the array vortex have opposite topological charges(l=±1).Due to the phase difference,the beam formed after the interference of the two array optical fields has a zero intensity "gap",forming a square array helix optical field in which the neighboring beams rotate in opposite directions with increasing propagation distance.In addition,this chapter gives the intensity distribution of the array helix optical field in the propagation process,analyzes the relationship between the number of spectral levels involved in the interference and the number of beams in the resulting optical field,and finally carries out experimental verification.5.Chapter 5 is a numerical calculation program designed based on GUI for generating the array optical field.The program can read the input parameters and perform calculation plotting,perform dynamic calculation and draw images according to the input real-time data,and also realize data and image clearing and program exit when the calculation is completed.The program provides a simple,fast and efficient way to study array optical field simulation and computation,especially in the process of optical field propagation can achieve real-time plotting,which can help researchers to understand the process of optical field propagation intuitively and clearly.6.Chapter 6 summarizes the work of this thesis and the outlook of the next work. |
