Simultaneous refractive index and temperature sensing based on chiral metasurface with dual quasi-bound states in the continuum

Abstract Chiral metasurfaces have emerged as a powerful platform for sustaining high-quality-factor chiral resonances and ultra-narrowband circular dichroism (CD), enabling ultrasensitive detection in diverse fields. In this work, we propose a chiral metasurface that supports dual quasi-bound states in the continuum (Q-BICs) modes by introducing a single in-plane asymmetry parameter, which permits the simultaneous measurement of seawater salinity and temperature. Rigorous scattering calculations reveal the two modes corresponding to toroidal dipole and magnetic-dipole resonances. Moreover, the CD of these dual Q-BIC modes can be flexibly tailored by tuning the chiral asymmetry parameters, providing additional degrees of freedom for performance optimization. Numerical simulations show that both modes undergo significant spectral shifts in response to variations in refractive index (RI) and temperature. The calculated sensitivities are 223.83 nm RIU −1 and 261.42 nm RIU −1 to RI changes, and 0.20 nm °C −1 and 0.22 nm °C −1 to temperature changes, respectively. These results underscore the exceptional chiral sensing capability of the metasurface. This work exhibits significant sensitivity against sensing variation, which offers a multifunctional approach for multiparameter measurement applications.