Ultranarrow Dual-Band Perfect Absorption in Visible and Near-infrared Regimes Based on Three-Dimensional Metamaterials for Ultrahigh-Sensitivity Sensing

We theoreticallydemonstrate the realization of the ultranarrow dual-band perfect absorption at visible range in 3D metamaterials comprising Au vertical split-ring resonators (VSRRs) array above a thick Au film for high-sensitivity sensing. By placing the 3D metamaterial of Au VSRRs directly onto the Au substrate to remove the dielectric substrates effect, the simulated results reveal that ultranarrow dual-band perfect absorption with the two narrow absorption bandwidth of 7.3 nm and 1.1 nm in the visible regime can be excited from pure magnetic plasmon (MP) resonance and via the strong coupling between the MP resonance of the VSRRs and the surface plasmons polaritons (SPPs) propagating on the Au film, respectively. Moreover, coupling effects in the VSRRs with different structural parameters also are studied in detail. Because of the ultranarrow dual-band perfect absorption of the VSRRs being extremely sensitive to the changes of the material surrounding, our proposed 3D metamaterial exhibits ultrahigh sensitivity (S= 918 nm/RIU,S*= 680/RIU) and figure of merit (FoM= 835,FoM*= 4.5×106) in near-infrared regime, which hold potential applications in label-free biosensing.