Nonlinear thermoplasmonics in graphene nanostructures

TL;DR

This paper demonstrates that thermoplasmons in narrow graphene nanoribbons can be excited at mid- and near-infrared frequencies, leading to significant third-harmonic generation and Kerr nonlinearities, with potential for non-invasive nonlinear optical applications.

Contribution

It reveals that thermoplasmons in graphene nanostructures can be activated at IR frequencies and induce strong nonlinear effects via photothermal excitation, avoiding electrical gating.

Findings

Thermoplasmons in narrow graphene nanoribbons can be activated at IR frequencies.

Significant third-harmonic generation observed.

Strong optical Kerr nonlinearities demonstrated.

Abstract

The linear electronic dispersion relation of graphene endows the atomically thin carbon layer with a large intrinsic optical nonlinearity, with regard to both parametric and photothermal processes. While plasmons in graphene nanostructures can further enhance nonlinear optical phenomena, boosting resonances to the technologically relevant mid- and near-infrared (IR) spectral regime necessitates patterning on $\sim10$ nm length scales, for which quantum finite-size effects play a crucial role. Here we show that thermoplasmons in narrow graphene nanoribbons can be activated at mid- and near-IR frequencies with moderate absorbed energy density, and furthermore can drive substantial third-harmonic generation and optical Kerr nonlinearities. Our findings suggest that photothermal excitation by ultrashort optical pulses offers a promising approach to enable nonlinear plasmonic phenomena in nanostructured graphene that avoids potentially invasive electrical gating schemes and excessive charge carrier doping levels.