Third harmonic generation in graphene and few-layer graphite films

TL;DR

This study demonstrates third harmonic generation in graphene and few-layer graphite, revealing layer-independent nonlinear optical properties and quantifying the material's third-order susceptibility.

Contribution

It provides the first measurement of third harmonic generation in graphene and shows that the susceptibility is independent of layer number for few layers.

Findings

Third harmonic emission scales with the cube of incident intensity.

Effective third-order susceptibility is on the order of 1e-16 m^2/V^2.

Harmonic emission scales with the square of the number of layers.

Abstract

We observe optical third harmonic generation from graphene and few-layer graphite flakes produced by exfoliation. The emission scales with the cube of the intensity of the incident near-infrared femtosecond pulses and has a wavelength that is one-third of the incident wavelength, both consistent with third harmonic generation. We extract an effective third-order susceptibility for graphene that is on the order of 1e-16 square meter per square volt, which is comparable to that for materials that are resonantly excited, but larger than for materials that are transparent at the fundamental and third harmonic wavelengths. By measuring a set of flakes with different numbers of atomic layers, we find that the emission scales with the square of the number of atomic layers, which suggests that the susceptibility of graphene is independent of layer number, at least for a few layers.