南京大学 现代工程与应用科学学院，江苏 南京 210023
大尺寸、大数值孔径、宽波段的消色差平面透镜设计是成像技术的一个瓶颈性问题，也是近年来超构透镜研究领域的一个重要挑战，主要原因是透镜的各个参量之间存在内禀的制约关系。文中结合消色差透镜的群时延理论及透镜的相位分布，通过理论分析给出各参量之间的半定量制约关系。同时，分别通过拓扑优化和直接二值搜索的方法，设计了不同参量下的消色差超构透镜和多阶衍射透镜，发现在保持效率80%左右的前提下，透镜尺寸增加了一倍，数值孔径或波段宽度减少了一半，而透镜厚度则随尺寸成线性增长。该结果表明，这两类平面透镜具有相同的內禀参数依赖关系，即透镜尺寸与数值孔径和波段宽度呈现反相关、与透镜厚度呈现正相关的关系，这与理论预测基本一致。
平面透镜 消色差 参量优化 flat lens achromatism parameter optimization 红外与激光工程
2020, 49(9): 20201032
Author Affiliations
Abstract
Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education & Hunan Provincial Key Laboratory of Low-Dimensional Structural Physics and Devices, School of Physics and Electronics, Hunan University, Changsha 410082, China
Based on the triangular lattice two-dimensional photonic crystal (PC), the lattice spacing along the transverse direction to propagation is altered, and a gradient PC (GPC) flat lens is designed. The band structures and equal frequency curves of the GPC are calculated; then, the imaging mechanism and feasibility are analyzed. The imaging characteristics of the GPC flat lens are investigated. It is observed that the GPC can achieve multiple types of super-resolution imaging for the point source. This GPC lens is allowed to be applied to imaging and other fields such as filtering and sensing.
photonic crystal super-resolution imaging flat lens negative refraction gradient lattice spacing Chinese Optics Letters
2020, 18(12): 120501
Author Affiliations
Abstract
Centre for Micro-Photonics, Faculty of Engineering, Science and Technology, Swinburne University of Technology, John Street, Hawthorn, VIC 3122, Australia
Graphene oxide (GO) ultrathin flat lenses have provided a new and viable solution to achieve high resolution, high efficiency, ultra-light weight, integratable and flexible optical systems. Current GO lenses are designed based on the Fresnel diffraction model, which uses a paraxial approximation for low numerical aperture (NA) focusing process. Herein we develop a lens design method based on the Rayleigh-Sommerfeld (RS) diffraction theory that is able to unambiguously determine the radii of each ring without the optimization process for the first time. More importantly, the RS design method is able to accurately design GO lenses with arbitrary NA and focal length. Our design is experimentally confirmed by fabricating high NA GO lenses with both short and long focal lengths. Compared with the conventional Fresnel design methods, the differences in ring positions and the resulted focal length are up to 13.9% and 9.1%, respectively. Our method can be further applied to design high performance flat lenses of arbitrary materials given the NA and focal length requirements, including metasurfaces or other two-dimensional materials.
ultrathin flat lens graphene oxide Rayleigh-Sommerfeld diffraction Fresnel diffraction Opto-Electronic Advances
2018, 1(7): 180012
郑州大学 信息工程学院 河南省激光与光电信息技术重点实验室, 河南 郑州 450052
大多数渐变光子晶体渐变透镜都是以正方晶格或三角晶格排布为基础, 并且多选择硅或二氧化硅等高折射率材料, 研究的波段多为红外波段。随着可见光通信技术的发展, 在可见光波段研究低折射率材料的自聚焦透镜变得很有意义。为了迎合这种需求, 提出了Sun-flower型渐变光子晶体自聚焦透镜。首先, 通过比较TE和TM两种偏振模式Sun-flower渐变光子晶体朗伯透镜在可见光波段的会聚强度, 发现TM型的会聚效果远远优于TE型。然后, 以TM型Sun-flower渐变光子晶体为基础设计圆柱形自聚焦平板透镜, 通过光场传输的模拟计算给出平板透镜在可见光波段自聚焦的拍长, 进一步优化平板透镜会聚光强设计透镜的层数, 结果表明在层数为22时效果最佳。最后, 讨论了列数的减少对平板透镜的影响, 结果表明随着列数的减少光强减弱。这对于制作出高性能会聚效果、短焦距、小体积的光学集成器件有重要的指导意义。
自聚焦透镜 渐变光子晶体 朗伯透镜 平板透镜 self-focusing lens Sun-flower Sun-flower graded photonic crystals luneburg lens flat lens 红外与激光工程
2017, 46(11): 1120002
