关键词: 光学涡旋/
轨道角动量/
计算全息图/
光通信技术
English Abstract
Detection optical vortex topological charges with monocyclic multistage intensity distribution
Zhang Hao1,Chang Chen-Liang2,
Xia Jun2
1.Department of Physics, Southeast University, Nanjing 211189, China;
2.School of Electronic Science and Engineering, Display center, Southeast University, Nanjing 210096, China
Received Date:30 September 2015
Accepted Date:23 November 2015
Published Online:05 March 2016
Abstract: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 multistage 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.
Keywords: optical vortices/
orbital angular momentum/
computer generated hologram/
optical communication technology
