Plasmon-assisted high-harmonic generation in graphene

TL;DR

This paper demonstrates that doped graphene nanostructures can efficiently generate high-order harmonics through plasmonic enhancement, offering a tunable, compact platform for ultrafast light sources with unprecedented harmonic intensities.

Contribution

It introduces a novel approach to high-harmonic generation using plasmonic effects in doped graphene nanostructures, combining strong near-field enhancement with intrinsic nonlinearity.

Findings

Efficient broadband HHG predicted in doped graphene nanostructures.

No cutoff observed in harmonic order unlike atomic systems.

High harmonic intensities can be tuned by incident light and nanostructure geometry.

Abstract

High-harmonic generation (HHG) in condensed-matter systems is both a source of fundamental insight into quantum electron motion and a promising candidate to realize compact ultraviolet and ultrafast light sources. Here we argue that the large light intensity required for this phenomenon to occur can be reached by exploiting localized plasmons in conducting nanostructures. In particular, we demonstrate that doped graphene nanostructures combine a strong plasmonic near-field enhancement and a pronounced intrinsic nonlinearity that result in efficient broadband HHG within a single material platform. We extract this conclusion from time-domain simulations using two complementary nonperturbative approaches based on atomistic one-electron density-matrix and massless Dirac-fermion Bloch-equation pictures. High harmonics are predicted to be emitted with unprecedentedly large intensity by tuning the incident light to the localized plasmons of ribbons and finite islands. In contrast to atomic systems, we observe no cutoff in harmonic order. Our results support the strong potential of nanostructured graphene as a robust, electrically tunable platform for HHG.