An Enhanced High Q-Factor Resonance of Quasi-Bound States in the Continuum With All-Dielectric Metasurface Based on Multilayer Film Structures

Abstract

Confinement of light is very important to the field of optics, and it is theoretically possible to achieve the perfect confinement for optical modes located in the continuous domain radiation state. Achieving perfect confinement is possible for bound states in the continuum (BIC), which localize waves that lie in the continuous spectrum of the radiative state and remain in a perfect localized state. In this article, we propose a metasurface that consists of arrays of silicon nanoellipsoidal pairs and calculate its transmission spectra and energy bands. Based on an all-dielectric metasurface, a dielectric multilayer film is incorporated to improve the quality factor of the array composed of ellipsoidal table pairs by an order of magnitude. By breaking the symmetry of ellipsoidal table pairs, quasi-BIC resonance modes excited by electric quadrupole (EQ) and magnetic dipoles (MDs) are realized using asymmetric silicon nanoellipsoid surfaces, where the quasi-BIC modes have high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}$ </tex-math></inline-formula> -factors. In this article, the relationship between the structural asymmetry of Fano resonance controlled by symmetry-protect BICs and the radiation <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}$ </tex-math></inline-formula> -factor is analyzed and demonstrated theoretically. At the same time, we use quasi-BIC resonances in asymmetric silicon nanoellipsoidal pairs of metasurfaces to achieve a huge Goos–Hänchen (GH) shift enhancement, which exceeds the third-order wavelength and a very large group index to achieve excellent slow-light effects. Our work is centered on the design of simulations for the BIC metasurface. Meanwhile, based on the simulation design results, we propose to advance the application of optical communication devices, BIC sensing, optical switches, and optical modulators.