Abstract
We present a metasurface composed of graphene ribbon superlattice that supports plasmonic Fano resonance in a simple symmetric configuration. Without the necessity of changing the geometry size of graphene ribbons, we tune the Fano resonance of the metasurface containing identical graphene ribbons by simply changing the global or local periods of the superlattice. The increase of the global period of the superlattice leads to a blue-shift of the broad resonance of the bright mode, while the increase of the local period leads to simultaneous shifts of the broad resonance of the bright mode and the sharp resonance of the dark mode toward opposite direction with respect to each other. The resonance shift mechanism can be well explained by the restoring force model for longitudinal dipole arrays. In addition, the overall spectral position of the Fano resonance can be actively tuned by the fermi level of graphene ribbons. Our methods provide a simple and flexible pathway to tune the plasmonic Fano resonance, which holds great potentials for tunable biosensing and slow light applications with improved performance.
Highlights
Surface plasmon (SP) that is usually supported by nanostructures of noble metals is widely studied in the nanophotonic field due to its capability to confine light in subwavelength scale and the potential to miniaturize photonic devices
We present a metasurface composed of graphene ribbon superlattice that supports plasmonic Fano resonance in a simple symmetric configuration
Graphene has been reported as a novel plasmonic material beyond noble metals [1]–[5], as the plasmon frequency of graphene is tunable via electrostatic gating or chemical doping, and the propagating graphene plasmons (GPs), which are supported in a continuous graphene sheet, can be extremely confined down to volumes that are several orders of magnitude smaller than plasmons in noble metals, due to the extremely large propagation constants of the GPs
Summary
Surface plasmon (SP) that is usually supported by nanostructures of noble metals is widely studied in the nanophotonic field due to its capability to confine light in subwavelength scale and the potential to miniaturize photonic devices. To obtain tunable Fano resonance in graphene-based plasmonic metasurfaces, graphene ribbon with broken symmetry [27]–[29], complex graphene cut-wire combination [30], [31], graphene ring pairs with different sizes [32], [33] have been proposed. In those graphene metasurfaces, the Fano resonance is a result of the interference of two or more individual plasmonic resonant modes supported by multiple graphene structures with different geometries. The behavior of spectral shifts of the Fano resonance in graphene superlattice is significantly different from that in metallic nano-resonator superlattices where transverse dipole arrays are generally taken into consideration [38], [39]
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