Photonic Microcavity-Enhanced Magnetic Plasmon Resonance of Metamaterials for Sensing Applications

We first investigate numerically photonic microcavity-enhanced magnetic plasmon (MP) resonance in metamaterials for high-quality refractive index sensing. The metamaterials consist of a top periodic array of U-shaped metallic split-ring resonators (SRRs), a middle dielectric layer, and a bottom metallic backed plate. The top metallic SRRs that are placed at about Bragg distance above the bottom metallic plate constitute a photonic microcavity. Because the MP resonance excited in metallic SRRs is coupled to the photonic microcavity mode supported by the photonic microcavity, the radiative damping of the MP resonance is strongly reduced, and consequently, its linewidth is decreased dramatically. Benefiting from the narrow linewidth, large modulation depth, and giant magnetic field enhancement at the MP resonance, the cavity-coupled metamaterial sensor has very high sensitivity (S = 400 nm/RIU and S* = 26/RIU) and figure of merit (FOM = 33 and FOM* = 4215), which suggests that the proposed metamaterials have potential in applications of plasmonic biosensors.