An Ultra-Wideband Reflective Phase Gradient Metasurface Using Pancharatnam-Berry Phase

Baoqin Lin,Zhe Liu,Lintao Lv,Xiang Ji,Jianxin Guo,Jing Wu

doi:10.1109/access.2019.2894133

Abstract

Designing a transmissive and reflective phase gradient metasurface (PGM) using Pancharatnam-Berry (PB) geometrical phase must be based on an appropriate metasurface, which can realize circular-polarization (CP)-conversion transmission and CP-maintaining reflection, respectively. When an appropriate metasurface is proposed, a PGM can be easily constructed by gradually rotating the anisotropic or chiral resonators in different unit cells. In this paper, to design an ultra-wideband reflective PGM, first, an ultra-wideband CP-maintaining metasurface is proposed, and the numerical simulation results show that the proposed metasurface can realize CP-maintaining reflection at CP incidence between 8.43 and 26.93 GHz; in addition, a PB phase will be generated in its co-polarized reflection coefficient by rotating the anisotropic resonators in its unit cells. Thus, based on the metasurface, an ultra-wideband PGM is constructed successfully, the simulated and experimental results show that the PGM can realize ultra-wideband anomalous reflection at arbitrarily polarized incidence, and almost all the reflected waves at right-handed and left-handed CP (RHCP and LHCP) incidences will both be deflected to an anomalous direction; in addition, the reflected waves at linear and elliptical polarized (LP and EP) incidences will be separated into two beams for the LP and EP waves that can both be decomposed into a pair of RHCP and LHCP waves. Furthermore, finally, a detailed theoretical analysis is presented for the CP-maintaining reflection of the proposed metasurface.

Highlights

Metasurfaces are two dimensional metamaterials with subwavelength thickness, which usually consist of a planar array of resonant unit cells mounted on a dielectric substrate
We have measured its co-polarized scattering pattern at CP incidence by the method of measuring antenna pattern, the schematic illustration of our measurement setup is shown in Fig. 7(b), in which the laboratory sample is erected with these super units in horizontal direction, and two pairs of identical RHCP horn antennas are used, the transmitting antenna is fixed to emit a normal RHCP incident wave onto the laboratory sample, but the receiving antenna rotates around the laboratory sample in a horizontal plane to measure the co-polarized scattering pattern and find the maximum reflection direction at different frequencies
This work presents the design of an ultra-wideband reflective phase gradient metasurface (PGM) using PB phase

Summary

Introduction

Metasurfaces are two dimensional metamaterials with subwavelength thickness, which usually consist of a planar array of resonant unit cells mounted on a dielectric substrate. The key to designing a PGM is how to make a metasurface structure generate a phase gradient under an EM wave incidence. Gradually changing the size and shape of the resonators in different unit cells can make the resonant frequency of each resonator different, let the array of resonators have space-variant phase response and generate a phase gradient under an EM wave incidence. This method is a common one, which can be used to design various PGMs, even about polarization-independent PGMs. The second method is to use a so-called Pancharatnam-Berry (PB) geometrical

Methods

Results

Conclusion