Refractive index sensing utilizing tunable polarization conversion efficiency with dielectric metasurface

Conventional metal metasurfaces imparting abrupt local phase profiles suffer from strong inherent loss and limited polarizability, leading to low polarization conversion efficiency of electromagnetic fields and insensitive responses with changes of external environment. Here, by adopting lossless silicon nanopillars to constitute a dielectric gradient metasurface, an incident circularly polarized light can be partly converted to a transmitted light of opposite helicity. And the polarization conversion efficiency varies sensitively with the refractive index of surrounding media. Simulation shows that the intensities between 0th and 1st diffraction orders change oppositely with the liquid refractive index, the proposed dual-channel (0th and 1st diffraction orders) average sensitivity reaches 16.134 dB/RIU at a wavelength of 1550 nm. We also analyzed the biosensing characteristics of an ultrathin molecular layer of 30-nm-thick coated on the silicon nanopillars surface. The refractive index sensing utilizing dielectric metasurface that we reported has excellent performance, which has potential applications environmental monitoring, medicine, biochemical sensing, and optical regulations.