All-metallic high-efficiency generalized Pancharatnam–Berry phase metasurface with chiral meta-atoms

Jixiang Cai,Xingdong Feng,Fei Zhang,Xiaoliang Ma,Xiong Li,Yinghui Guo,Ting Xie,Yan Chen,Xiangang Luo,Mingbo Pu,Honglin Yu

doi:10.1515/nanoph-2021-0811

Abstract

Abstract 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.

Highlights

Metasurfaces, comprising subwavelength artificial structures, enable flexible manipulation of the phase, polarization, and amplitude of light in reflection or transmission mode owing to its extraordinary electromagnetic characteristics [1]
Metasurfaces based on the Pancharatnam– Berry (PB) phase have attracted significant attention in the domains of subwavelength optics and electromagnetics
A recent advance has demonstrated that the generalized PB phase representing multiple times of the rotation angle could be obtained with highfold rotational symmetry meta-atoms, but it suffers from the low cross-polarization conversion efficiency that impedes its further applications, especially for meta-atoms with rotational symmetry ≥3

Summary

Introduction

Metasurfaces, comprising subwavelength artificial structures, enable flexible manipulation of the phase, polarization, and amplitude of light in reflection or transmission mode owing to its extraordinary electromagnetic characteristics [1]. By judiciously designing the dimension, rotation, and position of each unit element with high spatial resolution, the additional phase gradient or surface momentum can be generated for wavefront engineering of light at will, which promotes the evolution of Snell’s law to generalized Snell’s law [2,3,4]. The wavefront manipulations of these functional metadevices rely on the propagation phase [19], geometric phase [20], detour phase [21], resonance phase [22], and others [23,24,25]. Cai et al.: All-metallic high-efficiency generalized Pancharatnam–Berry

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Results

Conclusion