Efficient generation of prominent and robust plasmonic Fano resonances in 3D metamaterials

We discuss our recent experimental and theoretical works on the efficient generation of prominent and robust Fano resonances in 3D metamaterials (MMs). The 3D MMs are formed by integrating vertical U-shape SRRs or vertical rectangular plates along a planar metallic hole array with extraordinary optical transmission (EOT) built by means of homemade focused ion-beam (FIB) lithography [1, 2]. In such a configuration, intensified vertical E-field is induced along the metallic holes and naturally excites the electric resonances of the vertical structures, which form non-radiative “dark” modes due to the symmetry constraints. These 3D conductive “dark” modes strongly interfere with the “bright” resonance mode of the EOT structure, which generate significant Fano resonances with both prominent destructive and constructive interferences. Moreover, compared with the capacitive and inductive coupled Fano resonances that degrade drastically upon small structural deviations, the demonstrated 3D conductive coupling induced Fano resonances are highly scalable, universal, robust and immune against both fabrication and illumination imperfections. These 3D MM with prominent and robust Fano resonances exhibit very high optical sensing performance with a sensitivity up to 2040 nm/RIU at the near infrared wavelength around 1550 nm.