High Circular Dichroism Chiral Sensor Based on the Combination of Nanorods and Annular Cylinders

Chiral materials are crucial components in the natural world, and the exploration of chiral materials hold significant importance in advancing areas such as chiral sensing, bio-marking. The integration of Bound States in the Continuum (BICs) in the design of chiral metasurfaces has emerged as a focal point in optical research, offering widespread research value and practical applications. The chiral dielectric metasurface proposed in this paper is formed by a combination of silicon nanorod, annular cylinder, and silicon dioxide substrate. Through selective detaching, we simultaneously break the structural mirror symmetry and in-plane inversion symmetry, thereby eliciting quasi-BICs and intrinsic chirality. This design achieves dual-band chiral responses, yielding a maximum circular dichroism (CD) of 0.979 and a Q-factor of 1517.5. By adjusting the structural parameters, the tunability of the structure is achieved. The study of the sensing performance of the metasurface resulted in a maximum sensitivity (S) of 270.6 nm/RIU and a maximum Figure of Merit (FOM) of 587.5. Additionally, By comparing the sensing performance with achiral structure, we verified the enhancement of sensing performance through chiral effects. The proposed chiral metasurface advances the practical application of chirality in fields such as biosensing.