障碍物遮挡下漂移涡旋光束拓扑荷数的测量  

Measurement of Topological Charge of Obstructed Wandering Vortex Beams

作　　者：李岩松 陈君 傅钢坤 戚国震 石岩 赵春柳 金尚忠 Li Yansong;Chen Jun;Fu Gangkun;Qi Guozhen;Shi Yan;Zhao Chunliu;Jin Shangzhong(College of Optical and Electronic Technology,China Jiliang University,Hangzhou 310018,Zhejiang,China)

机构地区：[1]中国计量大学光学与电子科技学院,浙江杭州310018

出　　处：《光学学报》2023年第2期226-235,共10页Acta Optica Sinica

基　　金：浙江省之江实验室重大科研项目(2019DE0KF01);浙江省重点研发计划项目(2021C01068)。

摘　　要：复杂环境中漂移扰动和不透明障碍物破坏光振幅和光相位,给拓扑荷数(TC)精准测量带来挑战。分析了两种均匀离轴的多中心涡旋光束和一种随机离轴的漂移涡旋光束经扇形不透明障碍物(SSOO)后的传输情况,提出一种利用单柱透镜测量漂移涡旋光束TC的方法。对比光强法、傅里叶变换法以及相位法在极端条件下对漂移涡旋光束TC测量的结果,发现在以上3种方法失效时,所提方法仍可对输入光束的TC值大小及符号作出准确判断。这种抗光束漂移和抗遮挡的TC测量法对基于涡旋光的光通信和光加密具有重要应用价值。Objective Topological charge(TC)is a key factor to characterize the orbital angular momentum(OAM)of vortex beams.Accurate determination of TC is an essential prerequisite for the applications of OAM beams in optical communication and sensing.In complex environments,wandering perturbation and opaque obstacles destroy the amplitude and phase of the optical field and put challenges to accurate measurements.In this paper,we propose a method to determine the TC of obstructed wandering vortex beams.According to the theoretical results of the propagation of two uniform off-axis multi-center vortex beams and a random off-axis wandering vortex beam through a sector-shaped opaque obstacle(SSOO),it is observed that the averaged OAM of wandering vortex beams can reveal the TC of the input field,and even wandering perturbation and large-angle SSOO are encountered.Experimental measurement of the averaged OAM is carried out based on a single cylindrical lens(CL),and the results agree with the theoretical predictions.Results show that the method proposed here works well when the methods of light intensity,Fourier transform,and phase distribution fail to determine the TC in extremely complex environment such as the angle of SSOO of 270°and large wandering perturbations.Methods In this work,three types of multi-center off-axis vortex beams,namely,the beams of uniform off-axis coherent superposition(UCS),uniform off-axis incoherent superposition(UIS),and random off-axis incoherent superposition(RIS),are studied both in theory and experiment.In the theory part,utilizing an equivalent matrix method(EMA),we obtain the propagation of the three types of vortex beams after the SSOO.Theoretical results of the distribution of the light intensity,Fourier intensity,and phase are presented.According to the ABCD propagation law of a tilted CL,the average OAM of the three types of beams is calculated for various input topological charges.In the experimental part,the intensity distribution is detected,and the average OAM is obtained using a sin

关 键 词：物理光学 涡旋光束 轨道角动量 光束漂移 障碍物 拓扑荷探测 

分 类 号：TN247[电子电信—物理电子学]