Broadband gate-tunable terahertz plasmons in graphene heterostructures

By B. Yao, Yuan Liu, Shu-Wei Huang, Chanyeol Choi, Zhenda Xie, J. F. Flor Flores, Yu Wu, Mingbin Yu, D. Kwong, Yu Huang and 3 more. 2017

163 citations recorded by the source corpus.

Graphene, a unique two-dimensional material comprising carbon in a honeycomb lattice1, has brought breakthroughs across electronics, mechanics and thermal transport, driven by the quasiparticle Dirac fermions obeying a linear dispersion2,3. Here, we demonstrate a counter-pumped all-optical difference frequency process to coherently generate and control terahertz plasmons in atomic-layer graphene with octave-level tunability and high efficiency. We leverage the inherent surface asymmetry of graphene for strong second-order nonlinear polarizability4,5, which, together with tight plasmon field confinement, enables a robust difference frequency signal at terahertz frequencies. The counter-pumped resonant process on graphene uniquely achieves both energy and momentum conservation. Consequently, we demonstrate a dual-layer graphene heterostructure with terahertz charge- and gate-tunability over an octave, from 4.7 THz to 9.4 THz, bounded only by the pump amplifier optical bandwidth. Theoretical modelling supports our single-volt-level gate tuning and optical-bandwidth-bounded 4.7 THz phase-matching measurements through the random phase approximation, with phonon coupling, saturable absorption and below the Landau damping, to predict and understand graphene plasmon physics.An all-optical difference frequency process is exploited to generate terahertz graphene plasmons that are tunable over an octave.

Subfields: Atomic and Molecular Physics, and Optics, Biomedical Engineering, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/3c3a00df4433d7d272aa733a0891bebb7708d552