Si-grating-assisted SPR sensor with high figure of merit based on Fabry-Perot cavity

A type of Si-grating refractive index biosensor based on surface plasmon resonance (SPR) is proposed and analyzed within the near-infrared region. The finite element method is used for the simulation process. The surface plasmons can be excited more efficiently by adding a spacer layer between the grating and the thin metal film. More importantly, the dip strength of the reflectivity curve can be tailored by tuning the thickness of the spacer layer. Due to Fabry-Perot (F-P) cavity resonance enhancement, the maximum sensitivity can reach up to 1820 nm/RIU with figure of merit as high as 293.5 RIU-1. The performances obtained in the proposed sensor are more competitive than those reported in the literatures.