Dual-polarization and dual-band quasi-BIC metasurface for tunable absorption and high-sensitivity sensing

Abstract

Symmetry-protected bound state in the continuum (SP-BIC) is a typical representative of BIC to excite high-quality factor (Q factor) resonances. At the same time, most studies on SP-BIC support only one polarization direction and one quasi-BIC (Q-BIC). Here, an all-dielectric metasurface is designed to achieve a dual-polarization and dual-band Q-BIC resonance. Oblique incidence can also excite Q-BIC resonances, enabling adjustment of the Q factor via incident angle. The physical mechanism of the dual-polarization BIC is analyzed by calculating eigenmodes and performing a multipole decomposition. We covered a single-layer graphene sheet over the all-dielectric metasurface, resulting in a dual-band absorber that operates in two orthogonal polarization directions. The sensing performance of an all-dielectric metasurface is investigated, and the Q-BIC resonance shows gas-sensing sensitivity up to 635 GHz/RIU and a liquid-sensing sensitivity up to 436.8 GHz/RIU. Our multifunctional all-dielectric metasurface demonstrates significant potential to enhance light-matter interactions and paves the way for the development of high-performance sensors, lasers, and absorbers.