【作者】 张蕾；

【导师】 柯熙政； 崔真；

【作者基本信息】 西安理工大学 ， 通信与信息系统， 2020， 硕士

【摘要】 携带轨道角动量(Orbital Angular Momentum,OAM)的涡旋光束具有相位奇点且波前相位呈螺旋结构分布。在OAM复用通信系统中因OAM模式之间具有正交性,则在同一波长上可实现OAM复用,使其在信息编码,信息传输和数据存储等方面有着广泛的应用。本文以OAM复用通信系统为背景,研究了多环涡旋光束的产生及其在大气湍流中的传输特性,主要工作如下:1、介绍了常见的涡旋光束类型,并以典型的拉盖尔-高斯光束为例,推导了正交叠加产生双环及三环涡旋光束的光强和相位表达式,仿真分析了不同光源参数情况下多环涡旋光束的光强和相位分布特性,给出了多环涡旋光束的光强和相位分布随着单个涡旋光束拓扑荷数改变时的变化规律。2、搭建了利用空间光调制器产生双环涡旋光束的实验平台,实现了在同号和异号的拓扑荷数情况下双环涡旋光束的产生,验证了多环涡旋光束产生的合理性和有效性。3、理论研究了双环涡旋光束的传输机理,并利用随机相位屏模拟了大气湍流介质,继而研究了双环涡旋光束在不同大气湍流强度下传输后光强和相位分布的变化情况。研究结果表明:正交叠加后产生的多环涡旋光束是互相独立的,其内环为拓扑荷数绝对值最小的涡旋光束,外环为拓扑荷数绝对值最大的涡旋光束。拓扑荷数绝对值的差值越大,环与环之间的间距越大。双环涡旋光束在大气湍流中传输之后其光场受到大气湍流的影响而发生畸变,且随着湍流强度越大,畸变越严重。由于多环涡旋光束携带不同OAM模式,可同时传输不同的信息,则可提高通信容量和通信编码能力,对通信编码领域有重要意义。更多还原

【Abstract】 The vortex beam carrying Orbital Angular Momentum has a phase singularity and the wavefront phase is distributed in a spiral structure.In the OAM multiplexing communication system,due to the orthogonality between the OAM modes,the OAM multiplexing can be realized at the same wavelength,which makes it widely used in the fields of information coding,information transmission and data storage.Based on the OAM multiplexing communication system,this paper studies the generation of multi-ring vortex beams and their transmission characteristics in atmospheric turbulence.The main work is as follows:1.The common types of vortex beams are introduced,and taking the typical Laguerre-Gaussian beam as an example,the intensity and phase expressions of double-ring and three-ring vortex beams produced by orthogonal superposition are derived.At the same time,the intensity and phase distribution characteristics of multi-ring vortex beams under different light source parameters are simulated and analyzed,and the variation rules of intensity and phase distribution of multi-ring vortex beams with the topological charge of a single vortex beam are given.2.An experimental platform for generating a double-ring vortex beam using a spatial light modulator was built,and the double-ring vortex beam was generated under the topological charge number of the same sign and different sign.Therefore,the rationality and effectiveness of multi-ring vortex beams are verified.3.Theoretically studied the transmission principle of the double-ring vortex beam,and the stochastic phase screen was used to simulate the atmospheric turbulent medium,and then the change of the light intensity and phase distribution after the double-ring vortex beam was transmitted under different atmospheric turbulence intensity was studied.The results show that the multi-ring vortex beams generated after orthogonal stacking are independent of each other,the inner ring is the one with the smallest absolute value of the topological charge,and the outer ring is the one with the largest absolute value of the topological charge.The greater the difference in the absolute value of the topological load between the rings,the greater the spacing.After the double-ring vortex beam propagates in atmospheric turbulence,its light field is distorted by the influence of atmospheric turbulence,and as the intensity of turbulence increases,the distortion becomes more severe.Since the multi-ring vortex beam carries different OAM,different information can be transmitted at the same time,which can improve the communication capacity and communication coding ability,which is of great significance to the field of communication coding.更多还原