Edge and waveguide terahertz surface plasmon modes in graphene microribbons

Abstract

Surface plasmon modes supported by graphene ribbon waveguides are studied and classified. The properties of both modes with the field concentration within the ribbon area (waveguiding modes) and on the edges (edge modes) are discussed. The waveguide and edge modes are shown to be separated from each other by a gap in wave numbers. The even-parity hybridized edge mode results to be the fundamental electromagnetic mode of the ribbon, possessing also the lowest losses. All of the plasmonic modes in the ribbons have an optimum frequency, at which the absorption losses are minimum, due to compromise between the plasmon confinement and the decrease of the group velocity close to the modal cutoff. The presented results show that the diffraction limit in graphene ribbons can be surpassed.

Real-space mapping of tailored sheet and edge plasmons in graphene nanoresonators

“…A comprehensive experimental characterization of graphene plasmonic nanoresonators and their sheet and edge modes has thus been elusive so far. On the other hand, plasmonic edge modes have been shown to propagate along sharp edges of gold films, graphene and 2D electron gases 11,[23][24][25][26][27][28] and provide stronger confinement of the electromagnetic fields compared to the sheet plasmons.Here we image and analyze the near-field structure of both plasmonic sheet and edge modes in graphene disks and rectangular nanoresonators. We employ scattering-type scanning near-field optical microscopy (s-SNOM) 29 , which to date is the only available tool for real-space imaging of the propagation and confinement characteristics of graphene plasmons 8,9,11 .…”

“…A comprehensive experimental characterization of graphene plasmonic nanoresonators and their sheet and edge modes has thus been elusive so far. On the other hand, plasmonic edge modes have been shown to propagate along sharp edges of gold films, graphene and 2D electron gases 11,[23][24][25][26][27][28] and provide stronger confinement of the electromagnetic fields compared to the sheet plasmons.…”

Electrospinning for nano- to mesoscale photonic structures

“…Solid, 1D organic nanorods (ONRs) with moderate aspect ratio and high surface area have provided good performance for supercapacitor electrodes [86] and greatly improved photostability for biological imaging applications [126]. Graphene plasmonics [127][128][129][130] have provided gate tunability [131,132], and the momentum mismatch between incident waves and plasmons can be overcome through the fabrication of graphene nanostructures such as nanoribbons [133][134][135][136][137][138][139][140][141].…”

Graphene Sandwiches as a Platform for Broadband Molecular Spectroscopy

“…Thanks to its vanishing thickness and linear dispersion, ribbons made out of graphene exhibit a particular mode spectrum which was investigated in detail by Nikitin and co-workers. 29 Although sheets which are vertically spaced produce the expected symmetric and anti-symmetric combinations of the surface plasmons 34 known as short and long-range modes within the plasmonic community, 40 the transparency of graphene and the extremely confined modes propagating along the edges 41,42 complicate and enrich markedly the hybridization process. Christensen et al studied thoroughly those modes focusing on narrow ribbons where the contribution from the edges was greatest and derived a useful scaling law in order to predict their spectral behaviour in paired ribbons.…”

“…[26][27][28] The most impressive of which is probably the extreme compression of these surface waves with lateral confinement extending only a few nanometres away from the graphene sheet. [29][30][31][32][33] Furthermore, the transparency of graphene gives rise to particular hybridized modes in coupled sheets. 34 This is even more striking in paired ribbons where the contribution from the edges can result in unexpected field profiles.…”