Research On The Detection Method Of Photon Orbital Angular Momentum Mode

Due to the orthogonality and high-dimensionality of photon orbital angular momentum(OAM),high-dimensional quantum communication based on OAM modes and multiplexed optical communication based on OAM modes(without additional bandwidth)have recently attracted wide attentions,however,and to accurately measure OAM mode is still a challenge.In this paper,the topological charge detection of photon orbital angular momentum,the intensity and phase capture of orbital angular momentum beams are studied.The main work and results are as follows:(1)Considering the helical phase structure and Gouy phase characteristics of OAM beams,we propose a detection method for the topological charge of OAM modes based on the number and rotation angle of petal patterns formed by interfering OAM modes.Using the relationship between the number of petal patterns formed by interfering OAM modes and the topological charge of input OAM mode,and the different rotation angles of petal patterns at different propagation distances,the topological charge value of input OAM mode can be calculated effectively by measuring the rotation angles of petal patterns.We first deduce the relationship between the rotation angle of the petal patterns formed by interfering OAM modes,topological charge value and propagation distance,and then we present the method to obtain the topological charge value of the input OAM mode by the number and rotation angle of petal patterns formed by interfering OAM modes.Numerical simulation and experimental results show that this method can simultaneously detect the symbol and topological charge of the input OAM mode,and has high fault tolerance.(2)Considering the constructive and destructive interference between the local plain wave and the received OAM mode,we propose a method to capture the amplitude profile and phase profile of the received OAM beam simultaneously.The received OAM mode is interfered with the local plain wave at the receiving end,and two charge-coupled devices(CCDs)are used to record the constructive and destructive interference patterns,respectively.With different phase settings of local plain waves,such as ?/2 and ?,the amplitude profile and phase profile of the received OAM mode can be simultaneously captured from the two interferences and the four interference patterns.We first theoretically analyze the amplitude profile and phase profile of the received OAM modes from the constructive and destructive interference patterns,and we verify the feasibility of this method through simulation and experiment.The results show that the method can simultaneously capture the amplitude and phase profile of single OAM mode and the superimposed OAM mode,and even in the environment of turbulent atmosphere,this method can simultaneously capture the amplitude and phase profile of the received OAM mode,which has a strong robustness.