单环多段光强分布检测光学涡旋拓扑荷值

摘要

Generation and application of the vortex beams are part of the hot topics in the optical field. In connection with the limited detection range of topological charge, we introduce a novel monocyclic multistage intensity distribution, which is generated by the coaxial superposition of two vortex beams with different topological charge numbers which have the same radius of ring in the focal plane of fraunhofer diffraction. This novel intensity distribution which is achieved by computer generated hologram is a new application of sidelobe-modulated optical vortices. The detection range of topological charge is expanded to 128 by two detection constants consisting of segments and radius in the monocyclic multistage intensity distribution method. We study the generation and distribution characteristics of monocyclic mul-tistage intensity distribution in the focal plane of fraunhofer diffraction theoretically and experimentally to generate the qualified monocyclic multistage intensity distribution using a spatial light modulator. Excellent agreement between theoretical and experimental results is observed. The study indicates that two orbital angular momenta of vortex beams can be accurately determined by the segments and radius determined in the monocyclic multistage intensity distribution method. The method is immune to harassments from alignment and phase matching between the beams and optical elements, and has a large detection range, which is enlarged one order of magnitude compared with the previous way of detecting topological charges with sidelobe-modulated optical vortices. Our method provides a more large detection range of topological charge, which enables the vortex beams as the information carriers to carry more data in communication. Therefore, this method possesses research potential and applicability in future free-space optical communication.%针对涡旋光束检测范围局限这一问题，提出了一种新的光学涡旋拓扑荷值检测方法--单环多段光强分布检测法，它以分段数和环半径为两大检测常数，将检测涡旋光束拓扑荷值范围扩大到了128种，与以往利用旁瓣调控光学涡旋检测拓扑荷值方法相比，检测范围扩大了1个数量级。单环多段光强分布是基于计算机全息图实现在远场衍射焦平面上环半径相等的两束携带不同拓扑荷数的涡旋光束叠加后形成的光强分布。计算机模拟和光学实验验证了所提出方法的可行性，该方法在自由空间光通信领域具有一定的研究价值和应用潜力。