涡旋光束是波前相位为螺旋状的特殊光束，其光子携带轨道角动量(orbital angular momentum，OAM)。OAM具有无穷大的离散取值空间，可作为通信中一种全新的维度，带来巨大的信息带宽。而光信号中OAM状态的检测、识别，是实现OAM通信的关键步骤和重要环节，对OAM检测方法和基于OAM的通信方法的研究，具有重要的科研意义和潜在的应用前景。因此，本文对涡旋光束的OAM模式检测和通信应用做出研究，主要研究内容包括：

(1)阐述了涡旋光束的基本原理和其衍射传播特性，对常见的涡旋光产生和OAM检测方法进行了理论推导和实验验证。并针对传统OAM检测识别效率低下的问题，对相位匹配方法进行改进，提出了基于相位匹配序列的OAM检测方法。首先，采用一组时序循环的螺旋相位，对待测光束进行相位匹配；之后，通过增加4f系统和偏移相位调制，使得匹配后的高斯光束，转移到与OAM模式相关的空间位置上。仿真及光学实验结果表明，该方法相比传统方法具有更高的检测识别效率。

(2)针对相位匹配序列检测OAM导致的光场降维和信息丢失问题，对相位匹配序列法进行改进，在几何变换法的基础上，提出了二维向量输出的OAM检测方法。该方法采用一组不同环径狭缝滤波的螺旋相位序列，对不同极径上的光场进行提取和相位调制，实现匹配光斑转移到与拓扑核数和极径相关的二维空间位置上。仿真结果表明，该方法的输出光场具有同输入光场一致的维度和信息，能进一步实现光场重建。

(3)利用不同OAM模式涡旋光束可以携带不同符号信息的特点，将不同OAM模式的涡旋光脉冲作为不同逻辑值的码字，进行编码。采用16种OAM模式不同的涡旋光束，实现了八位二进制信号编码和扩展编码空间的四位四进制数据信号编码，然后利用相位匹配法对OAM光脉冲序列解码，从而直接判读获得原始信息，实现编码光束与信息数据的反映射。仿真实验表明，设计的编解码方案具有可行性。

Vortex beam is a special beam with spiral wavefront phase, and its photons carry orbital angular momentum (OAM). OAM has infinite discrete value space, which can be used as a new dimension in communication and bring huge information bandwidth. The detection and identification of OAM state in optical signal is the key step and important link to realize OAM communication. The research on OAM detection method and communication method based on OAM has important scientific research significance and potential application prospect. Therefore, this paper studies the OAM mode detection and communication application of vortex beam. The main research contents include:

(1)The basic principle and diffraction propagation characteristics of vortex beam are studied. The common vortex light generation and OAM detection methods are theoretically deduced and experimentally verified. Aiming at the low efficiency of traditional OAM detection and recognition, the phase matching method is improved, and an OAM detection method based on phase matching sequence is proposed. Firstly, a set of spiral phases with sequential cycles are used to match the phase of the light beam to be measured; Then, by adding 4f system and offset phase modulation, the matched Gaussian beam is transferred to the spatial position related to OAM mode. Simulation and optical experiment results show that this method has higher detection and recognition efficiency than traditional methods.

(2)Aiming at the problem of light field dimensionality reduction and information loss caused by OAM detection by phase matching sequence, the phase matching method is improved. Based on the geometric transformation method, an OAM detection method with two-dimensional vector output is proposed. This method uses a set of helical phase sequences filtered by slits with different ring diameters to realize the light field extraction and phase modulation on different polar diameters. Then, through offset and phase modulation, the matching spot is transferred to the two-dimensional spatial position related to the topological kernel and polar diameter. The simulation results show that the output light field of this method has the same dimension and information as the input light field,so as to further realize the reconstruction of light field.

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