Study On Wavefront Control And Application Of Vector Beams

Optical beams can be characterized by two important parameters: amplitude and phase.In addition,polarization is another important parameter of the optical beams.A vector beams is usually refers to the beam with inhomogeneous distribution of polarization states on its wavefront.In recent years,with the depth study on the vector beams,the vector properties of light and the interaction between the vector beam and matter have become an important research content in many fields such as optical detection and metrology,display technology,data storage,optical communications,materials science,astronomy,and biology.Focusing of the vector beams through the scattering medium has become one of the hot spots.Thus,how to generate the required polarization and complex amplitude of the vector beams,as well as how to control the polarization of the optical field passed through scattering media,are two important issues in this research field.The aim of this thesis is mainly to theoretically and experimentally explore new methods for generation and control of vector beams and the applications in focusing through scattering media.The main contents of the thesis are as follows:1.Basic concepts,research background,latest progress and existing problems in research field of vector beams are reviewed and analyzed.The paper summarizes the methods of vector beam wavefront modulation based on spatial light modulator a focusing of the vector beams through scattering media,and analyzes the shortcomings and limitations of the existed methods.2.Based on Jones matrix theory,the mathematical description method of general and typical vector beams is analyzed and discussed,and a method for calculating the uniform spatial diffraction and transmission of simulated vector beams is presented.Since the polarization state of the vector beams can be characterized by the Jones element,this chapter gives the theoretical analysis of the polarization of the vector beams using the Jones matrix and gives the characterization method of the polarization sensitive material and the device based on the Jones matrix.Then,the diffraction properties of the vector beams are simulated numerically based on the scalar diffraction theory.Finally,based on vector diffraction theory,the theoretical analysis and computer simulation of the radial vector beams focusing characteristics are carried out.3.A new method for generating vector beams with arbitrary polarization and complex amplitude distributions based on a birefringent beam splitter(BBS)and liquid crystal spatial light modulator(LC-SLM),together with the theoretical analysis and experimental results are given.This method does not require complicated optical path,and the needed optical elements are also very simple without optical elements between the SLM and the BBS.Using a polarization-selective computer-generated hologram displayed on the SLM,an arbittary complex vector beam can be generated from an input conventional Gauss beam.4.A method for fast and precisely measuring the complex vector transmission matrix(VTM)of ananisotropic scattering medium is proposed.In this method,a simple vector SLM unit composed of a conventional transmittance LC-SLM and a small-angle BBS is introduced to realize the programmable control of both the amplitudes and phases of the two orthogonal polarization components of the input vector beam point by point.At the same time,a two-channel angular-multiplexing polarization holographic recording geometry is adopted to realize the synchronous holographic measurement of the two orthogonal polarization components of the scattered light field.Using this method,the vector transmission matrix of typical scattering media(such as ZnO)is measured and the distribution and evolution characteristics of vector transmission matrix are analyzed.5.A method for control of vector focusing through a scattering medium based on the vector SLM and the angular-multiplexing polarization holography is proposed.In this method,the amplitude,phase and polarization distributions of the input beam to the scattering medium is controlled by a vector SLM,which significantly extend the focusing control in the range and the freedom.In combination with the method for measuring the VTM of a scattering medium,an experimental system for dynamically control of vector focusing through a scattering medium is designed.Using this system,we successfully realize focusing a vector beam through anisotropic multiple-scattering media such as ZnO scattering layers.6.A method is proposed to generate arbitrory vector beams based on the theoretical analysis based on the thin film polarizing prism,and the test results are given.Although the introduction of the birefringent crystal in this method can greatly simplify the system and improve the quality of the generated vector beams,it also brings some disadvantages when different wavelengths or ultrashort pulse beams are involved.Compared with the system using a birefringent beam splitter with unadjustable splitting angle,the polarization splitting angle in the improved system can be adjusted by slightly rotating the related mirrors,which will bring some more convenience when different wavelengths and different pixel sizes of SLMs are involved.We also demonstrated that the system possesses a good polarization-selective imaging ability.The system provides two independent polarization encoding and imaging channels and the point spread functions corresponding to the two imaging channels could be respectively controlled by the SLM;and so different output images with different polarization states could be obtained and processed.