Cai Jixiang, Zhang Fei, Pu Mingbo, Chen Yan, Guo Yinghui, Xie Ting, Feng Xingdong, Ma Xiaoliang, Li Xiong, Yu Honglin, Luo Xiangang
State Key Laboratory of Optical Technologies on Nano-Fabrication and Micro-Engineering, Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu, 610209, China.
Key Laboratory of Opto-electronic Technology and Systems of the Education Ministry of China, Chongqing University, Chongqing, 400044, China.
Nanophotonics. 2022 Feb 24;11(9):1961-1968. doi: 10.1515/nanoph-2021-0811. eCollection 2022 Apr.
Metasurfaces based on the Pancharatnam-Berry (PB) phase have attracted significant attention in the domains of subwavelength optics and electromagnetics. Conventional theory predicts that the PB phase is exactly twice the rotation angle of the anisotropic meta-atoms. Differently, a recent advance has demonstrated that the generalized PB phase representing multiple times of the rotation angle could be obtained with high-fold rotational symmetry meta-atoms, but it suffers from the low cross-polarization conversion efficiency (the theoretical upper limit of 25%) that impedes its further applications, especially for meta-atoms with rotational symmetry ≥3. Here, we verify that the chiral meta-atoms with high-fold rotational symmetries could produce the generalized PB phase. Besides, the all-metallic configuration is utilized to design C2, C3, and C5 chiral catenary meta-atoms to improve their efficiency and bandwidth. The equivalent air waveguide with low loss between two adjacent meta-atoms is formed to analyse the higher performances of the all-metallic scheme for the realization of the generalized PB phase compared with the metal-insulator-metal and all-dielectric C3 meta-atoms. As a proof of concept, four metadevices including two spin-Hall metadevices and two holograms are experimentally demonstrated and their maximum efficiency could exceed 83% in simulation. This work could provide a high-efficiency platform for the study of the generalized PB phase in linear and nonlinear optics.
基于潘查拉特纳姆-贝里（PB）相位的超表面在亚波长光学和电磁学领域引起了广泛关注。传统理论预测，PB相位恰好是各向异性超原子旋转角度的两倍。不同的是，最近的一项进展表明，具有高倍旋转对称性的超原子可以获得表示旋转角度倍数的广义PB相位，但其交叉极化转换效率较低（理论上限为25%），这阻碍了其进一步应用，特别是对于旋转对称性≥3的超原子。在此，我们验证了具有高倍旋转对称性的手性超原子可以产生广义PB相位。此外，利用全金属结构设计了C2、C3和C5手性悬链线超原子，以提高其效率和带宽。通过在两个相邻超原子之间形成低损耗的等效空气波导，分析了与金属-绝缘体-金属和全介质C3超原子相比，全金属方案在实现广义PB相位方面的更高性能。作为概念验证，实验展示了包括两个自旋霍尔超器件和两个全息图在内的四个超表面器件，其在模拟中的最大效率可超过83%。这项工作可为线性和非线性光学中广义PB相位的研究提供一个高效平台。
