Exploring the tuning mechanism of multipolar quasi-continuous domain bound states in tetramer metasurface

Abstract

High-quality factor (high-<i>Q</i>) resonance has broad prospects in applications such as in narrow-band filtering, slow-light devices, and nonlinear optics interaction enhanced to highly sensitive sensing. Previous methods of designing high-<i>Q</i> resonance suffered intrinsic drawbacks such as high-volume cavities or large-scale bending radii. However, recently, a new approach to designing high-<i>Q</i> resonances has begun to attract public attention on the basis of asymmetric metasurfaces that are related to the bound states in the continuum (BIC) phenomenon. Constructing BIC resonance in electromagnetic metasurface can generate sharp resonant transmission peak. Therefore, there is growing interest in utilizing BIC to achieve metasurface with high-<i>Q</i>. However, most of existing studies are based on single BIC, and few studies focusing on multiband BICs and multiple forms of symmetry breaking. In this work, we propose an all-dielectric metasurface composed of tetrameric cuboids. By etching two elliptical cylinders in each cuboid, the metasurface can simultaneously support in-plane symmetry breaking, displacement perturbations and periodic perturbations. We first use multipole calculations to analyze the physical mechanism by which the metasurface generates quasi-BIC under these three conditions. It is confirmed that the <i>Q</i> factor and resonant peak position of quasi-BIC can be controlled by adjusting the asymmetry parameters. Subsequently, we introduce the in-plane symmetry breaking, displacement perturbations and periodic perturbations into the metasurface simultaneously and generate five quasi-BIC modes, whose numbers and positions can be flexibly adjusted, and the largest <i>Q</i> factor is 58039. In summary, this work provides a new practical design concept for realizing high-<i>Q</i> all-dielectric metasurfaces, which can be used to improve the sensitivity of multi-parameter sensors.