Giant structurally modulated intrinsic chirality of quasi-bound states in continuum

Structurally modulated intrinsic chirality is a structural transformation phenomenon in photoresponsive molecules that is commonly utilized in biosensing and chemical analysis. In this study, we proposed an approach to achieve giant intrinsic chirality in a quasi-bound state in the continuum (Q-BICs)-slanted tetramer metasurface, where high Q factors and circular dichroism (CD) coexist. Empowered by the simultaneous resonance between toroidal dipole (TD) and electric quadrupole (EQ) modes, the intrinsic circular dichroism can be effectively tuned via variations in the slant angles of the metasurface. Our work not only addresses the lack of strong chiral materials in nature but also opens up new possibilities in chiroptical sensing, chemical analysis, and biotechnology.