High-quality dual-band perfect absorber based on the coexistence of quasi-bound states in continuum and anapole modes

Abstract Nanophotonic metamaterials exhibit application potential in micro/nano-optics owing to their unique optical properties. However, achieving dual-band perfect absorption with high quality factor remains a challenge. This study proposes a metamaterial featuring symmetry-broken silicon nanodisk arrays, which enables dual-band high- Q perfect absorption by transforming bound states in the continuum (BIC) into quasi-BIC and exciting an anapole mode. Numerical simulations demonstrate that the structure achieves absorption rates of 99.19% and 99.76% at wavelengths of 1068.55 nm and 1106.17 nm, respectively, with narrow linewidths of 1.08 nm and 0.84 nm, corresponding to Q -factors as high as 989 and 1316. Due to the polarization sensitivity of BIC, the absorption peaks can be switched on and off by adjusting the incident light polarization angle, offering a novel strategy for optical switching. Furthermore, as a dual-channel refractive index sensor, the metamaterial exhibits excellent sensing performance, with sensitivities of 81.9 nm RI U − 1 and 139.5 nm RI U − 1 , and figures of merit of 75.83 RI U − 1 and 166.1 RI U − 1 . This work not only provides a new design route for ultra-high- Q dual-band perfect absorbers, but also offers technical support for cutting-edge applications such as dual-frequency channel sensor and photonic switching.