Highly confined low-loss plasmons in graphene–boron nitride heterostructures

Abstract

Graphene plasmons were predicted to possess simultaneous ultrastrong field confinement and very low damping, enabling new classes of devices for deep-subwavelength metamaterials, single-photon nonlinearities, extraordinarily strong light-matter interactions and nano-optoelectronic switches. Although all of these great prospects require low damping, thus far strong plasmon damping has been observed, with both impurity scattering and many-body effects in graphene proposed as possible explanations. With the advent of van der Waals heterostructures, new methods have been developed to integrate graphene with other atomically flat materials. In this Article we exploit near-field microscopy to image propagating plasmons in high-quality graphene encapsulated between two films of hexagonal boron nitride (h-BN). We determine the dispersion and plasmon damping in real space. We find unprecedentedly low plasmon damping combined with strong field confinement and confirm the high uniformity of this plasmonic medium. The main damping channels are attributed to intrinsic thermal phonons in the graphene and dielectric losses in the h-BN. The observation and in-depth understanding of low plasmon damping is the key to the development of graphene nanophotonic and nano-optoelectronic devices.

Edge and Surface Plasmons in Graphene Nanoribbons

“…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.…”

Plasmonics in atomically thin materials

“…In this context, a search for better plasmonic materials has been initiated with a view to reducing absorption [31][32][33][34]. Recently, highly doped graphene has emerged as a promising alternative [35][36][37][38][39][40][41][42][43][44][45], combining huge field confinement and enhancement with comparatively lower losses [43,46], as well as large electrical tunability of its optical response [47][48][49][50]. These properties hold great potential for electro-optics applications, such as fast light modulation via electrostatic gating [38,39,[41][42][43][44], which has been demonstrated with the achievement of frequency variations spanning a whole octave [43].…”

A Thresholdless Tunable Raman Nanolaser using a ZnO–Graphene Superlattice

“…[14][15][16] A key advantage of doped semiconductors is that the plasmon frequencies are tunable in a wide range with varied doping level. For atomic-scale hybrid heterorstructure, the rich physics at interface of the hybrid heretostructure enable novel tunable optics for effective subdiffractional confinement of light [17][18][19][20][21] Here we report the growth of ZnOgraphene superlattice via a spatially confined reaction method. [22] We demonstrate room-temperature thresholdless tunable Raman lasing in freestanding ZnO-graphene superlattice, covering the near-infrared to visible wavelength region with varied pump laser.…”