Multiple Photonic Bound States in the Continuum in an Electromagnetically Induced Transparency Metasurface

Abstract

Bound state in the continuum (BIC), as a novel eigenmode with infinitely high-quality factor, has received great attention in modern optical science. Mode coupling in dielectric metasurfaces opens possibilities in searching for robust BICs. Here, we discover multiple BICs in periodic dielectric resonators composed of a silicon rectangular bar and a silicon ring in one lattice. For the symmetry-protected BIC at-Γ point, a sharp electromagnetically induced transparency window can be formed by either tilting incident angle to induce the ‘bright-bright’ mode coupling, or by displacing the ring to generate the ‘bright-dark’ mode coupling. Besides, the coupling between two resonators leads to a new energy band in the dielectric metasurface. As a result, two off-Γ BICs are formed owing to avoided crossings with two energy bands, and another one belongs to the single-resonance parametric BIC. Thus, our coupled resonators possess superior abilities to judiciously engineer BICs via versatile physical mechanisms. Taking advantage exclusively of coupled resonators in dielectric metasurfaces provides fresh insights into the creation of both symmetry-protected and accidental BICs, which enables profound advancements in designing novel photonic devices.