Controlling graphene plasmons with resonant metal antennas and spatial conductivity patterns

Abstract

Graphene plasmons promise unique possibilities for controlling light in nanoscale devices and for merging optics with electronics. We developed a versatile platform technology based on resonant optical antennas and conductivity patterns for launching and control of propagating graphene plasmons, an essential step for the development of graphene plasmonic circuits. We launched and focused infrared graphene plasmons with geometrically tailored antennas and observed how they refracted when passing through a two-dimensional conductivity pattern, here a prism-shaped bilayer. To that end, we directly mapped the graphene plasmon wavefronts by means of an imaging method that will be useful in testing future design concepts for nanoscale graphene plasmonic circuits and devices.

Edge and Surface Plasmons in Graphene Nanoribbons

“…In nano-IR experiments, fringes originate from constructive interference between tip-launched and boundary-reflected plasmons (Figure 1a). [3][4][5][6][7][8][9][10][11][12] Apart from these familiar patterns, we also observed plasmonic characteristics due to ribbon confinement as the ribbon width (W) shrinks. First, the two principal fringes move closer to each other with decreasing W and consequently the total number of distinct fringes observable within GNRs decreases.…”

“…These fields have a wide range of in-plane momenta q thus facilitating energy transfer and momentum bridging from photons to plasmons. [3][4][5][6][7][8][9][10][11][12] Our GNR samples were fabricated by lithography patterning of high quality CVD-grown graphene single crystals 26 on aluminum oxide (Al2O3) substrates (Supporting Information). As discussed in detail below, the optical phonon of Al2O3 is below  = 1000 cm -1 ( Figure S2), allowing for a wide mid-IR frequency region free from phonons.…”

“…The representative near-field images of the GNRs with widths of W = 480, 380, 270 and 155 nm are shown in Figure 1c-f, where we plot the near-field amplitude s() normalized to that of the bare Al2O3 substrate (Supporting Information). As documented in previous studies [4][5][6][7][8][9][10][11][12] , s() is a direct measure of the z-component electric field amplitude |Ez| underneath the AFM tip. In our experiments, we kept p-polarized light beam incident along the ribbons (Figure 1a) to avoid direct excitation of resonance modes of ribbons.…”

“…1 In particular, surface plasmons in graphene are collective oscillations of Dirac quasiparticles that reveal high confinement, electrostatic tunability and long lifetimes. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] Plasmons in graphene are promising for optoelectronic and nanophotonic applications in a wide frequency range from the terahertz to the infrared (IR) regime. 16,17 One common approach to investigate plasmons is based on nano-structuring of plasmonic media.…”

Graphene as a Tunable Anisotropic or Isotropic Plasmonic Metasurface

“…Such coupling of radiation into graphene plasmons has already been shown both theoretically 27,28 and experimentally. 29 Alternatively, other works have shown coupling through relief corrugations or subwavelength gratings on which graphene is placed, [30][31][32][33][34] as well as patterned graphene structures including 1D arrays of micro-ribbons 13,35 and 2D arrangements of islands. 25,[36][37][38] In order to achieve a periodic doping in the graphene, the sheet can be biased with the spatially periodic electrostatic field generated by a periodically corrugated plane, either metallic or dielectric (see Fig.…”