Dual‐Band Chiral Nonlinear Metasurface Supported by Quasibound States in the Continuum

Abstract

AbstractThis paper presents an all‐dielectric chiral metasurface composed of an array of two‐layer distorted square structures with nanoholes. This metasurface can simultaneously generate dual‐band opposite chiral responses, which can be attributed to the bound states in the continuum (BICs) and the distorted chiral structure. By combining the BICs with chirality, a dual‐band chiral nonlinear metasurface and a chiral‐sensing method are proposed. The simulated results show that the third harmonic generation (THG) conversion efficiency can reach the order of 10−4 for two peaks with a peak‐pump intensity of approximately 5.3 GW cm−2 in the near‐infrared region. Moreover, the third‐harmonic circular dichroism for each peak can reach up to 0.99 and ‐0.94, respectively. Furthermore, it is theoretically demonstrated that this metasurface can be used for chiral sensing with high sensitivities. These results provide new insights for linear and nonlinear spin‐dependent applications.