Bound state in the continuum and polarization-insensitive electric mirror in low-contrast metasurface

TL;DR

This paper introduces a low-contrast dielectric metasurface with radially anisotropic SiO2 and WS2, achieving polarization-insensitive electric mirrors and bound states in the continuum with high Q factors, suitable for integrated photonics.

Contribution

It presents a novel low-contrast metasurface design using doping to realize BIC and electric mirror effects, expanding practical applications of dielectric metasurfaces.

Findings

Achieved polarization-insensitive electric mirror in low-contrast metasurface.

Demonstrated ultrahigh Q factor BIC with negligible out-of-plane radiation.

Showcased doping as an effective strategy for low-contrast metasurface design.

Abstract

High-contrast refractive indexes are pivotal in dielectric metasurfaces for inducing various exotic phenomena, such as the bound state in the continuum (BIC) and electric mirror (EM). However, the limitations of high-index materials are adverse to the practical applications, thus low-contrast metasurfaces with comparable performance are highly desired. Here we present a low-contrast dielectric metasurface comprising radially anisotropic cylinders, which are SiO2 cylinders doped with a small amount of WS2. The cylinder exhibits unidirectional forward superscattering originating from the overlapping of the electric and magnetic dipole resonances. When normal illumination by a near-infrared plane wave, the metasurface consisting of the superscattering constituents manifests a polarization-insensitive EM. Conversely, when subjected to an in-plane incoming wave, the metasurface generates a symmetry-protected BIC characterized by an ultrahigh Q factor and nearly negligible out-of-plane energy radiation. Our work highlights the doping approach as an efficient strategy for designing low-contrast functional metasurfaces and sheds new light on the potential applications in photonic integrated circuits and on-chip optical communication.