Chiral metasurface sensing performance analysis based on bound states in the continuum

Abstract

Chirality is a typical phenomenon in nature that has significant optical research and practical applications. But natural chiral materials typically exhibit a weak chiral response, making it challenging to detect them with great sensitivity. Chiral metasurfaces can greatly increase circular dichroism (CD), efficiently improve the interaction between light and chiral molecules, and enhance chiral sensing. Additionally, combining bound states in the continuum (BIC) to excite numerous high-Q-factor Fano resonances is a useful strategy for enhancing sensing performance in all-dielectric metasurfaces. With its extremely small linewidth and exceptionally high Q value, the Fano resonance created by the quasi-BIC mode can significantly boost the performance of the refractive index sensor. In this study, we combine BIC with chirality, break the structure's mirror and inversion symmetry to construct a chiral all-dielectric metasurface structure based on BIC. Fano resonances with simultaneously high Q value and strong CD are achieved for the chiral optical response. Meanwhile, we investigate its sensing properties to obtain high sensitivity and figure of merit (FOM) for refractive index sensing performance. Our research offers suggestions for applications such as the identification and separation of chiral biological substances.