Electromagnetic field coupling characteristics in graphene plasmonic oligomers: from isolated to collective modes

Abstract

In this paper, we propose a plasmonic tetramer composed of coupled graphene nanodisks. The transformation from the isolated to the collective modes of the proposed structure is investigated by analysing the whispering-gallery modes and extinction spectra with various inter-nanodisk gap distances. In addition, the effect of introducing a central nanodisk into the tetramer on the extinction spectra is explored, which leads to Fano resonance. Furthermore, the refractive index sensing properties of the proposed graphene plasmonic oligomer have been demonstrated. The proposed nanostructures might pave the road toward the application of graphene plasmonic oligomers in fields such as nanophotonics, and chemical or biochemical sensing.

Effect of Nanodisks at Different Positions on the Fano Resonance of Graphene Heptamers

“…Usually, Fano resonance can be obtained by two approaches [26]. One approach is to destroy the symmetry of the structure [33,34].…”

“…Therefore, six nanodisks with in-phase oscillation generate the superradiant bright mode. However, the subradiant dark mode is caused by the interference between the central nanodisk and the ring nanodisks when a central nanodisk is added into structure [26]. The Fano resonance occurs when two modes couple with each other.…”

“…First, due to the high ohmic loss of metals [26,27], the cluster suffers huge absorption loss [27]. Secondly, when the geometrical structure of clusters is determined, the frequency range of PMs is hard to adjust according to other conditions, which leads to the difficulty of further development of functional structures [26]. Fortunately, the graphene-guided SPPs wave shows lower ohmic loss and higher electromagnetic field confinement ability.…”

Multiple Fano Resonances with Tunable Electromagnetic Properties in Graphene Plasmonic Metamolecules

“…Therefor multiple FRs are applied in multi-wavelength surface-enhanced Raman spectroscopy (SERS) [2,27]. However, due to the high ohmic loss and the obstacle in varying permittivity of noble metals [28,29], the quality of LSPR is degraded [30]. Furthermore, the working wavelength is unchangeable once the geometrical structures of the PMs are ascertained, which restricts the feasible applications in the fields of light-matter interaction, nanoantenna, chemical sensing, and biochemical sensing [31][32][33].…”

“…At the same time, the FR produced by GPs have a sharp spectra response. Moreover, due to the adjustable chemical potential of graphene, the Fano resonance produced by graphene has a wider application [28].…”