A High-Efficiency and Broadband Folded Reflectarray Based on an Anisotropic Metasurface for Generating Orbital Angular Momentum Vortex Beams

Zhen-Yu Yu,Yun-Hua Zhang,Huo-Tao Gao

doi:10.1109/access.2021.3088885

Zhen-Yu Yu, Yun-Hua Zhang + Show 1 more

Open Access

https://doi.org/10.1109/access.2021.3088885

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Abstract

In this paper, a low-profile folded reflectarray (FRA) assembled by an anisotropic metasurface is proposed to generate high-efficiency and broadband orbital angular momentum (OAM) vortex waves in the Ka band. In order to suppress the mutual coupling and increase the polarization conversion efficiency, a dual-polarization phase matching method (DPPMM) for helical wavefront construction is developed to achieve minimum phase compensation error in the orthogonal direction. A compact subwavelength anisotropic meta-atom with orthogonal || |-shaped structure is designed to achieve flexible wavefront manipulation and high-resolution phase compensation for x and y-polarization incident waves. After the optimization design, nearly 100% cross-polarization conversion efficiency for the anisotropic metasurface can be achieved at the working frequency of 12 GHz. To validate the proposed design method, an OAM FRA with 24×24 meta-atoms is fabricated and measured. The measurement results show that the aperture efficiency of the proposed FRA carried with the OAM mode l = 1 is significantly improved and reaches 20.2%. Moreover, the OAM bandwidth and 3-dB gain bandwidth reach 22.5% and 25%, respectively.

Highlights

In 1992, orbital angular momentum (OAM) as one of the essential physical quantities was first observed in the field of light [1]
The phase manipulation range of the square-shaped meta-atom cannot entirely cover 360◦ and the mutual coupling at the orthogonal direction is neglected for the anisotropic metasurface, which leads to a low-efficiency and narrow gain bandwidth for the proposed OAM folded reflectarray (FRA)
We developed a novel low profile FRA based on an anisotropic metasurface to generate high-efficiency and broadband vortex beams

Summary

INTRODUCTION

In 1992, orbital angular momentum (OAM) as one of the essential physical quantities was first observed in the field of light [1]. Yu et al.: High-Efficiency and Broadband FRA Based on Anisotropic Metasurface for Generating OAM Vortex Beams. In [28], a high polarization separation FRA is proposed to generate vortex beam with OAM mode l = 1. The size of the proposed meta-atom is larger than half wavelength, which causes difficulty for the anisotropic metasurface to construct the helical wavefront phase with high-resolution, resulting in a low aperture efficiency for this OAM FRA. The phase manipulation range of the square-shaped meta-atom cannot entirely cover 360◦ and the mutual coupling at the orthogonal direction is neglected for the anisotropic metasurface, which leads to a low-efficiency and narrow gain bandwidth for the proposed OAM FRA. An FRA composed of the anisotropic metasurface is proposed and investigated for generating the high-efficiency and broadband OAM beam.

CONCEPT AND WORKING PRINCIPLE

SIMULATION AND MEASUREMENT RESULTS

Findings

CONCLUSION