High-sensitivity terahertz chiroptical sensing enabled by multi-dimensionally tunable all-dielectric metasurface with dual quasi-bound states in the continuum

Chiral all-dielectric metasurfaces serve as an ideal platform for achieving high-Q chiral optical resonances and narrowband circular dichroism (CD), significantly enhancing sensing capabilities. We propose a single-layer metasurface that realizes dual q-BICs by introducing a single asymmetric parameter, which allows for greater selectivity in chiral responses without increasing structural complexity or requiring external stimuli. Moreover, the method of inducing dual-band chiral q-BICs to achieve CD is highly applicable to sensing, providing not only a broader spectral range for chiral sensing but also outstanding environmental and trace sensing capabilities. The sensitivity reaches up to 372.8 GHz/RIU and 23.6 GHz/µm, with figures of merit (FOM) of 297 RIU −1 . This offers a multifunctional approach for multi-band spin-selective transmission and chiral biosensing.