Second harmonic generation in multilayer graphene induced by direct electric current

TL;DR

This study demonstrates that applying a DC electric current to multilayer graphene significantly enhances its second harmonic generation (SHG) signal, with the effect being reversible and linearly proportional to current strength.

Contribution

It reveals a novel current-induced enhancement of SHG in multilayer graphene, explaining the effect through interference of reflected and current-induced SHG signals.

Findings

SHG intensity increases with applied current

SHG signal reverses sign with current direction

Effect explained by interference of SHG signals

Abstract

Optical second harmonic generation (SHG) is studied from multilayer graphene films in the presence of DC electric current flowing in the sample plane. Graphene layers are manufactured by chemical vapour deposition (CVD) technique and deposited on an oxidised Si(001) substrate. SHG intensity from graphene layer is found to be negligible in the absence of the DC current, while it increases dramatically with the application of the electric current. The current-induced change of the SHG intensity rises linearly with the current amplitude and changes its sign under the reversal of the current direction to the opposite. The observed effect is explained in terms of the interference of second harmonic radiation reflected from the Si surface and that induced by the DC current in multilayer graphene.