Generation of Half-Integer Harmonics and Efficient THz-to-Visible Frequency Conversion in Strained Graphene

TL;DR

This paper demonstrates how strain-induced pseudomagnetic fields in graphene enable efficient generation of half-integer and even harmonics, facilitating THz-to-visible frequency conversion with novel nonlinear optical properties.

Contribution

It reveals the role of pseudomagnetic fields in breaking symmetry and generating half-integer harmonics, advancing nonlinear optical applications in strained graphene.

Findings

Strain induces pseudomagnetic fields that break centrosymmetry.

Half-integer harmonics are generated depending on pulse duration.

Landau level structure influences harmonic generation.

Abstract

We study the generation of harmonics from graphene under the influence of an artificial magnetic field, generated via bending of a graphene flake. We show how the Landau level structure induced by the pseudomagnetic field breaks the centrosymmetry of graphene, thus allowing the generation of even harmonics. We also show, that depending on the impinging pulse duration, the nonlinear signal does not only contain the integer harmonics of the impinging pulse, but also its half-integer ones, due to the peculiar square-root-like nature of Landau levels in graphene.