Double Narrow Fano Resonances via Diffraction Coupling of Magnetic Plasmon Resonances in Embedded 3D Metamaterials for High-Quality Sensing

We theoretically demonstrate an approach to generate the double narrow Fano resonances via diffraction coupling of magnetic plasmon (MP) resonances by embedding 3D metamaterials composed of vertical Au U-shaped split-ring resonators (VSRRs) array into a dielectric substrate. Our strategy offers a homogeneous background allowing strong coupling between the MP resonances of VSRRs and the two surface collective optical modes of a periodic array resulting from Wood anomaly, which leads to two narrow hybridized MP modes from the visible to near-infrared regions. In addition, the interaction effects in the VSRRs with various geometric parameters are also systematically studied. Owing to the narrow hybrid MP mode being highly sensitive to small changes in the surrounding media, the sensitivity and the figure of merit (FoM) of the embedded 3D metamaterials with fabrication feasibility were as high as 590 nm/RIU and 104, respectively, which holds practical applications in label-free biosensing, such as the detection of medical diagnoses and sport doping drugs