Measurement And Analysis Of The Vortex Beam

Since the late twentieth century,in the past two decades,from 2G to 4G,to the upcoming 5G,mobile communication technology has developed at an unimaginable speed,and the communication rate has grown by almost leap.Nowadays,the development of social informationization is still rapidly improving,which has a greater demand for communication capacity.Therefore,exploring a method that can greatly expand the communication capacity has become a focus of attention.The vortex beam may achieve this demand.Because of the characteristics of orbital angular momentum and topological charge,the vortex beam has greater development prospects in the fields of optical communication,quantum information processing,photo-taking technology and optical imaging technology.However,at the same time,the vortex is relatively sensitive,and small disturbances will affect it.Therefore,we need to accurately measure and reliably analyze the changes that occur during the propagation of the vortex beam.In this paper,the theoretical analysis and experimental research on the basic characteristics of vortex light and the measurement and analysis methods of its mode are mainly carried out.The main contents are as follows:In the first chapter,through the investigation of the vortex-related literature,the development history of vortex light,the research status at home and abroad,its research value and significance are discussed,and several typical applications of vortex light are introduced.The second chapter mainly introduces the basic phenomena and theories of vortex light.It analyzes several basic characteristics of vortex light,and then introduces the types and characteristics of commonly used vortex beams.In the third chapter,the main methods of vortex beam generation are briefly introduced and their advantages and disadvantages are compared and analyzed.The principle of spatial light modulator and its application in optics are discussed.Finally,a method for testing the vortex beam is introduced and proved by experimental results.In the fourth chapter,the experiment is carried out by using four kinds of adjustable amplitude modulation methods and the pure phase modulation vortex beam hologram.The modulation function with the highest mode purity is selected for the light field reconstruction experiment.The theoretical basis of the model decomposition is provided,and the decomposition and reconstruction experiments of the vortex mode are carried out to verify the feasibility of this method.Then the definition of the orbital angular momentum density of the vortex beam is proposed.It is measured accurately by experiments,and the variation of OAM density when multiple OAM modes are superimposed and the relative phase changes continuously.Finally,a controllable OAM filter is designed,which uses andl??(28)94 four OAM modes to carry out experiments,which realizes filtering of any one or more OAM modes,discusses its shortcomings and measures or directions that can be improved.Finally,review and summarize the full text,and look forward to the prospects of the research work and the problems faced.