Highly sensitive and robust refractometric sensing by magnetic dipole of Si nanodisks

Silicon metasurfaces have been attracting interest in the sensing field because of their ability to support magnetic Mie resonance, low optical heating, and CMOS-compatible fabrication processes. Herein, we demonstrate that the sensitivity of the magnetic dipole (MD) mode for nanodisk Mie resonators (as high as 385 nm/RIU) is similar to the sensitivity of plasmonic metasurfaces and greater than that of the electric dipole (ED) mode of nanodisk Mie resonators. We also engineer the thickness of Mie resonators to achieve an MD-mode linewidth as small as 0.56 nm and a figure of merit greater than 160 RIU⁻¹. The measured sensitivity of the MD mode is more accurate than that of the ED mode, which is more prone than the MD mode to measurement errors arising from the partial filling of the liquid. Our study paves the way for the development of MD-mode-based dielectric biosensors for use in personal healthcare and medical diagnosis.