Photonic crystal assisted excitation of surface plasmons: a high-resolution refractive index sensor based on a gold spiral in a photonic crystal resonator

In this paper, an optical refractive index sensor based on a hybrid plasmonic-photonic crystal (P-PhC) topology for detection of various blood components is proposed. The sensor's structure is composed of a gold spiral resonator inside a rod-type hexagonal Si PhC cavity. The finite-difference time-domain method is used for the numerical investigation of the structures. The proposed hybrid sensor provides an astonishing figure of merit (FoM) of 2991 RIU-1 and fairly high sensitivity of 1675 nm/RIU. The maximum FoM achieved in this case is found to be 5 times higher than the conventional plasmonic sensors reported in the literature. For the proposed sensor, combining the stronger plasmonic light-matter interaction and the extraordinary confining properties of the PhC cavity contributes to the FoM enhancement. The proposed sensor can be used for sensing applications at optical communication wavelengths.