Interplay of bound states in the continuum empowers spectral-lineshape manipulation in all-dielectric metasurfaces

Abstract

The bound states in the continuum (BICs) in optical metasurfaces have latterly received prominent attention for their ultrahigh quality factors and the promise that they hold for realizing lowthreshold nanolasers, high-harmonic generation, and slow-light devices. In this scenario, the flexible tuning of the BIC is at the heart of multifunctional and tunable metadevices underpinning the central role in the modulation of optical spectral responses. Most BIC-inspired works are limited to single types of BICs modes only affected by the structural perturbation without tunable functionality, while different types of BIC modes have received little attention in manipulating the spectral line shapes in optical metasurface. Here, we show that the simultaneous generation and tailored interplay of two types of BIC modes can empower the realization of tailorable spectral lineshape manipulation in all-dielectric metasurfaces. In particular, the magnetic symmetry-protected BICs and accidental BIC result from the preserved reflection symmetry and geometrical parameter perturbation, respectively. The varied asymmetric parameters and the polarization angle of the incident light are responsible for the generation and interplay of the symmetry-protected and accidental quasi-BIC modes. Additionally, the interplaying quasi-BICs enable the implementation of the dual-wavelength passive optical switches throughout the related telecom bands, and can exhibit the tunable spectral features of different types of Fano resonances and EIT analog-based slow-light effect. These results could offer exploration potential for the development of multifunction and high-performance metadevices.