One-dimensional carbon nanostructures for terahertz electron-beam radiation

Abstract

One-dimensional carbon nanostructures such as nanotubes and nanoribbons can feature near-ballistic electronic transport over micron-scale distances even at room temperature. As a result, these materials provide a uniquely suited solid-state platform for radiation mechanisms that so far have been the exclusive domain of electron beams in vacuum. Here we consider the generation of terahertz light based on two such mechanisms, namely, the emission of cyclotronlike radiation in a sinusoidally corrugated nanowire (where periodic angular motion is produced by the mechanical corrugation rather than an externally applied magnetic field), and the Smith-Purcell effect in a rectilinear nanowire over a dielectric grating. In both cases, the radiation properties of the individual charge carriers are investigated via full-wave electrodynamic simulations, including dephasing effects caused by carrier collisions. The overall light output is then computed with a standard model of charge transport for two particularly suitable types of carbon nanostructures, i.e., zigzag graphene nanoribbons and armchair single-wall nanotubes. Relatively sharp emission peaks at geometrically tunable terahertz frequencies are obtained in each case. The corresponding output powers are experimentally accessible even with individual nanowires, and can be scaled to technologically significant levels using array configurations. These radiation mechanisms therefore represent a promising paradigm for light emission in condensed matter, which may find important applications in nanoelectronics and terahertz photonics.

Graphene plasmonic devices for terahertz optoelectronics

“…Theoretical studies have also suggested that the same band structure can potentially support population inversion and optical gain at THz frequencies under external carrier injection [13][14][15], depending on the detailed interplay of the intraband and interband relaxation dynamics. Second, graphene can feature ballistic electronic transport over μm-scale distances with record large room-temperature mobilities [16][17][18][19], and thus is an ideal materials system for THz sources based on high-frequency coherent carrier dynamics [20] and electron-beam radiation mechanisms [21][22][23]. Third, the collective oscillations of the graphene electron (or hole) gas can produce plasmonic resonances at THz or mid-infrared frequencies, as opposed to the visible or near-infrared excitations of traditional plasmonic nanostructures based on noble metals [10,[24][25][26][27].…”