Ultraviolet Sharp High-Order Magnetic Plasmon Based Fano Resonance of 3D Metamaterials

We theoretically study the ultraviolet sharp Fano resonances (FRs) produced through the optical diffraction coupling between the narrow collective surface mode supported by the array periodicity and the broad high-order magnetic plasmon (MP) mode in the three-dimensional (3D) metamaterials consist of aluminum vertical split-ring resonator (Al 3D-SRR) array. The linewidth of the second-order MP induced ultraviolet FR is as narrow as 7.3 nm due to the diffraction coupling feature of the magnetic fields. The intensity and position of the ultraviolet sharp FR are easily tuned by varying the array period as well as the base and arm length of the Al 3D-SRR structure. The conventionally defined performance index of optical sensors, sensitivity (
$S$
) and figure of merit (
FoM
) of our designed 3D metamaterial in the ultraviolet range, possess quite large values of 88 nm/RIU and 12, respectively.