Optical Third-Harmonic Generation in Graphene

TL;DR

This paper demonstrates strong third-harmonic generation in CVD-grown monolayer graphene on silica, revealing its nonlinear optical properties and enabling background-free imaging of graphene's structure.

Contribution

It reports the first observation of significant third-harmonic generation in CVD graphene with detailed polarization and azimuthal dependence analysis.

Findings

Third-harmonic signal exceeds bulk glass by over two orders of magnitude.

The process confirms expected symmetry properties of graphene.

Provides a new method for background-free imaging of graphene.

Abstract

We report strong third-harmonic generation (THG) in monolayer graphene grown by chemical vapor deposition (CVD) and transferred to an amorphous silica (glass) substrate; the photon energy is in three-photon resonance with the exciton-shifted van Hove singularity at the M-point of graphene. Our polarization- and azimuthal-rotation-dependent measurements confirm the expected symmetry properties for this nonlinear process. Since the third-harmonic signal exceeds that of bulk glass by more than two orders of magnitude, the signal contrast permits background-free scanning of graphene and provides insight into the structural properties of graphene.