In this article, the lineshape of Fano-like resonance of graphene plasmonic oligomers is investigated as a function of the parameters of the nanostructures, such as disk size, chemical potential and electron momentum relaxation time in mid-infrared frequencies. Also, the mechanism of the optimization is discussed. Furthermore, the environmental index sensing effect of the proposed structure is revealed, and a figure of merit of 25.58 is achieved with the optimized graphene oligomer. The proposed nanostructure could find applications in the fields of chemical or biochemical sensing.

The electromagnetic properties of the plasmonic dimer composed of coupled graphene nanodisks are numerically investigated in this paper. The results demonstrate that the degeneracy of the plasmonic modes of the dimer is lifted when the coupling is introduced. The evolution of the plasmonic mode, with the variation of inter-disk distance and the chemical potential of one of the nanodisks, is studied. The proposed structure might find broad areas of application including light–matter interaction, optical switching, directional emission of the plasmonic emitter, etc.

In the mid-infrared and terahertz (THz) regime, graphene supports tunable surface plasmon resonance (SPR) by controlling the chemical potential, which promotes light–matter interaction at the selected wavelength, showing exceptional promise for optoelectronic applications. In this article, we show that the electromagnetic (EM) response of graphene oligomers can be substantially modified by the modification of the local chemical potential, strengthening or reducing the intrinsic plasmonic modes. The effect mechanism is corroborated by a graphene nanocluster composed of 13 nanodisks with D_6h symmetry; by transforming to D_3h symmetry, the effect mechanism was retained and more available plasmonic resonance modes appeared. The intriguing properties open a new way to design nanodevices made of graphene oligomers with highly efficient photoresponse enhancement and tunable spectral selectivity for highly accurate photodetection.

Plasmonic trimers composed of equal-sized graphene nanodisks are proposed in this paper. The symmetry-breaking effect on the electromagnetic properties of the nanostructure is numerically investigated by studying plasmon energy diagrams and optical scattering spectra in mid-infrared range with a gradient vertex angle. The degenerate plasmonic modes are lifted and new modes appear with increased vertex angle. The energy diagrams are consistent with scattering extinction spectra, about which the dipole moment distribution of the proposed structure is discussed to demonstrate the coupling strength of the collective plasmonic modes of the trimer. More specifically, the frequency tunability of the plasmonic trimer is pointed out by modifying the chemical potential of the graphene nanodisks without varying the geometric configuration. The proposed structure might find applications such as light-matter interaction, single molecule detection, and high-sensitivity chemical sensing.

In this work, we demonstrate that the electromagnetic properties of graphene oligomer can be drastically modified by locally modifications of the chemical potentials. The chemical potential variations of different positions in graphene oligomer have different impacts on both extinction spectra and electromagnetic fields. The flexible tailoring of the localizations of the electromagnetic fields can be achieved by precisely adjusting the chemical potentials of the graphene nanodisks at corresponding positions. The proposed nanostructures in this work lead to the practical applications of graphene-based plasmonic devices such as nanosensing, light trapping and photodetection.

The formation of Fano resonance based on graphene heptamers with ${\mathit{D}}_{\mathbf{6}\mathit{h}}$ symmetry and the effect of nanoparticles at different positions on the collective behavior are investigated in this paper. The significances of central nanodisks on the whole structure are studied first by varying the chemical potential. In addition, the effect of six graphene nanodisks placed in the ring on collective behaviors is also investigated. The influence of the nanodisks at different positions of the ring on the Fano resonance spectrum of the whole oligomer is researched by changing the chemical potential and radius. The proposed nanostructures may find broad applications in the fields of chemical and biochemical sensing.