High Q all-dielectric metasurface sensor for seawater salinity and temperature simultaneous measurements

An all-dielectric hollow cylinder tetramer metasurface with two high Q resonances is proposed and numerically simulated in the near-infrared band. By researching the electromagnetic field distributions of the resonances at 1310.5 nm and 1359.0 nm, it can be proved that they are original from electric quadrupole (EQ) and magnetic dipole (MD). The Q-factor of the two resonances can be high up to 1024 and 45353, which is much higher than the previous work. The effect of the structural gap size on the resonance is also investigated. In addition, we studied the sensing performance of the metasurface for seawater salinity and temperature measurement, the maximum sensitivity can reach 0.0978 nm/‰ and 30 pm/°C, respectively. Salinity and temperature can be precisely identified based on the two sensing signals, so the proposed nanostructure is suitable for simultaneous detection of salinity and temperature in oceanography applications. And more possibilities are provided for developing high-performance sensors for ocean observation.