Photonic manipulation of the all-dielectric terahertz metasurface based on bound states in the continuum

Abstract

All-dielectric metasurfaces have been proven to be ideal platforms for manipulating electromagnetic waves and enhancing light-matter interactions. Recently, high quality factors resonances driven by bound states in the continuum (BICs) have attracted widespread attention in photonics. In this work, the symmetry protected at-Γ BICs and the accidental off-Γ BICs are both demonstrated in the metasurface composed of bi-nanohole arrays. In the considered terahertz band, for the monolayer metasurface, BICs can be controlled by regulating the size, shape, and arrangement of the bi-nanoholes, which improves the modulating depth of BICs. We also propose the bi-layer metasurface to prove the multiple BICs. It indicates the number of BICs of both types has a positive correlation with the layers of the metasurface so that we can get more BICs only by simply adding identical layers without introducing more complex patterns. Additionally, the multiple BICs are sensitive to the size and arrangement of the bi-nanoholes in each layer and the distance between layers. Furtherly, the multiple BICs have a good tolerance to the fabrication imperfection. The results here provide more modulation freedom for the artificial line shaping. The multiple BICs are useful for the design of multiple sensor devices.