Coupled plasmonic graphene wires: theoretical study including complex frequencies and field distributions of bright and dark surface plasmons
Theoretical research on localized surface plasmons (LSPs) supported by a structure formed by two parallel dielectric wires with a circular cross section wrapped with a graphene sheet has an impact in the practical realm. Here, LSPs are represented in the form of an infinite series of cylindrical multipole partial waves linked to each of the graphene wires. To obtain the kinematics (complex eigenfrequencies) and dynamic characteristics (field distributions) of the LSPs, we consider the analytic extension to the complex plane of the solution to the boundary value problem. The lower frequency LSP group is formed by four branches, two of them corresponding to bright modes and the others to dark…
Dyadic Green's function for the electrically biased graphene-based multilayered spherical structures
Abstract Dyadic Green's function for a multilayered spherical structure with alternating graphene-dielectric shells is extracted in this paper. To this end, the unknown expansion coefficients of the scattering superposition method are obtained by considering graphene local surface currents at the interface of two adjacent layers. To validate the formulas, the procedure of Mie scattering analysis employing our formulas is clarified and the extinction efficiencies of various graphene-based nanoparticles are computed. The possibility of using the proposed structure in the design of multi-band optical absorbers is discussed in detail. Moreover, a closed-form formula for obtaining the Purcell fa…
Multi-frequency super-scattering from sub-wavelength graphene-coated nanotubes
A cylindrical multilayered structure with three coupled graphene shells is shown to behave as a dual-band super-scatterer at mid-infrared frequencies. Under the 2D plasmonic nature of graphene material, multiple scattering resonances are attained in the deep subwavelength regime using an isotropic material. In the proposed structure, we efficiently exploit the existing three plasmonic resonances in each scattering channel. These resonances are tailored by dispersion engineering, which is simply displayed through the Bohr model applied to the associated planar structure. For the super-scatterer design, it is essential that the resonances of multiple channels coincide in a single frequency. H…
Multi-frequency near-field enhancement with graphene-coated nano-disk homo-dimers.
In this paper, a 3D sub-wavelength graphene-coated nano-disk dimer (GDD) is proposed for multi-frequency giant near-field enhancement. We observed that the dual-band operation originates from the excitation of hybridized localized surface plasmons on top and bottom faces of the disks along with the mutual coupling from the adjacent particle. Due to the sub-wavelength nature of the disks, the excited localized surface plasmons on the sidewalls are weak but they still can affect the dual operating bands. On the other hand, the strength and resonance frequency of the enhanced fields can be simply modulated by tuning the relative distances of 2D graphene disks on top and bottom faces. Adjustabl…