Research Of Integrated Photonic Devices To Generate And Measure Orbital Angular Momentum Beams

Light beams possessing an azimuthal phase structure carry orbital angular momentum.Due to the unique nature of OAM beams,they have attracted growing attentions and exhibited excellent potential applications in many fields,including micromanipulation,optical microscopy,sensing,optical communication and quantum information science.The research of OAM beams has become a hot topic in the recent years.Inevitably,generating and measuring OAM beams are important and challenging tasks.Different schemes have been presented to accomplish these tasks over the past decade.However,the complex system,which consists of discrete and bulk elements,is set up in most of the previous strategies and suffers from weight,instability and cost.On the other hand,the research of photonic integration is developing rapidly,and promotes the photoelectron technology into a new chapter.Compared to their bulk optics counterparts,devices based on the concept of photonic integration are significantly more compact and robust.Thus,the research of integrated schemes to generate and measure OAM beams is of great significance.The main content of the thesis is summarized as the followings:(1)The research background and research progress of OAM beams are introduced,and applications of light's OAM are discussed.The helical wavefront and orbital angular momentum of OAM beams are analyzed theoretically.Laguerre-Gaussian beams and Bessel beams,which are two typical and well-known representations of OAM beams,are described briefly.And then,several existing schemes to generate and measure OAM beams are sorted out and analysed.(2)A scheme for generating radial 1st-order OAM beams based on defect-symmetrical microdisk is proposed.The confined radial 2nd-order WGMs in the microdisk can be extracted into targeted radial 1st-order OAM beams by two concentric angular grating arrays.The purity of OAM beams is 0.6~0.9 in the simulation.(3)A compact and efficient approach to detecting OAM by self-interference using a plasmonic metasurface is proposed.The topological charge of light is revealed by the interferogram.In addition,the bandwidth of the metasurface is over a broad wavelength range from 1.52 to 1.6 ?m.Such a metasurface is able to detect OAM transparently without blocking the transmission link and shows great potential to be integrated with fiber and on-chip devices.