Simultaneous Measurement of Seawater Salinity and Temperature Based on Quasi-BIC Metasurface

Dielectric metasurface based on bound states in the continuum (BICs) have attracted significant attention recently due to their unique characteristics, such as ultra-high quality factors (Q-factor), narrow linewidths, and enhanced light-matter interactions. In this paper, we proposed a novel sensor design for the simultaneous measurement of seawater salinity and temperature based on an asymmetric dimer dielectric metasurface. By calculating the transmission spectrum of the metasurface, we observe two transmission dips corresponding to the toroidal dipole (TD) and magnetic dipole (MD) resonances. Specifically, the TD resonance is governed by breaking the translational symmetry (TS) protected BICs, while the MD resonance is excited by breaking the reflection symmetry (RS) protected BIC. Both dips exhibit shifts in response to changes in the refractive index (RI) or the temperature. Simulation results reveal that the sensing sensitivities of the two dips to RI are 212.56 nm/RIU and 327.85 nm/RIU, respectively, while the sensitivities to temperature are 0.04 nm/°C and 0.05 nm/°C, respectively. We believe that this work is very beneficial for the design of optical sensors for multi-parameter measurement applications.