Terahertz Nonlinearity in Graphene Plasmons

TL;DR

This paper investigates the nonlinear terahertz response of graphene plasmons in nanoribbons, revealing strong saturation effects and rapid energy relaxation, with implications for low-power nonlinear optical devices.

Contribution

It provides the first experimental measurement and theoretical modeling of terahertz nonlinear response and energy relaxation dynamics in graphene plasmons.

Findings

Strong saturation of plasmon absorption observed

Relaxation time of 10 ps measured

Nonlinearity enhanced by two orders of magnitude

Abstract

Sub-wavelength graphene structures support localized plasmonic resonances in the terahertz and mid-infrared spectral regimes. The strong field confinement at the resonant frequency is predicted to significantly enhance the light-graphene interaction, which could enable nonlinear optics at low intensity in atomically thin, sub-wavelength devices. To date, the nonlinear response of graphene plasmons and their energy loss dynamics have not been experimentally studied. We measure and theoretically model the terahertz nonlinear response and energy relaxation dynamics of plasmons in graphene nanoribbons. We employ a THz pump-THz probe technique at the plasmon frequency and observe a strong saturation of plasmon absorption followed by a 10 ps relaxation time. The observed nonlinearity is enhanced by two orders of magnitude compared to unpatterned graphene with no plasmon resonance. We further present a thermal model for the nonlinear plasmonic absorption that supports the experimental results.