Research On Mesurement Technology Of Orbital Angular Momentum Of Vortex Beam

With the booming development of information technology industry,emerging technologies such as block chain,cloud computing,immersive experience and big data have put forward higher requirements on the bandwidth capacity of communication network.Traditional communication technologies,such as frequency division,code division,time division and space division multiplexing,are used to improve the capacity and rate of communication channels,but they cannot meet the exponential growth of data demand.Therefore,the vortex beams that carry different orbital angular momentum have attracted extensive attention in the field of multiplexing communication.This multiplexing uses the infinite value of orbital angular momentum photons to carry out information loading so as to carry out multi-channel transmission.However,in the multiplexing receiver,the vortex light obtained by demultiplexing needs to be detected so as to ensure the correctness of the whole multiplexing system.Thus,the detection of single beam vortex is particularly important.The main content of this thesis is investigated in detecting orbital angular momentum of vortex beam and improving its performance by grating through the simulation and experiment.The main work is as follows:1.Numerical simulation simulated the formation of vortex light field,the generation of 2 kinds of gratings,phase correction diagram and fan-out periodic phase hologram;At the same time,the distribution of diffraction spots of vortex light field after grating diffraction is analyzed.2.On the basis of 1,the diffraction spot was improved by optical correction phase diagram and fan-out phase diagram to improve the detection results,then,the number of topological charges of vortex light that could be detected.3.Carried out experimental research on 1 and 2,built the vortex optical OAM detection system by loading grating and phase diagram on the spatial light modulator and using other optical components,and finally carried out experimental verification.The results show that:(1)vortex beam can be detected by the number of fringes and orientation of diffraction spots,and the maximum detectable topological charges can be increased to 30 after the improvement of the two technologies;(2)after the experimental research,it is found that the experimental results correspond to the simulation results one by one,which can verify that the two technologies can improve the detection effect,so that the detection of high-order vortex beam can be carried out to verify the correctness of demultiplexing,which is of great significance in the communication system of orbital angular momentum multiplexing of vortex beam.