Theory of plasmon-enhanced high-harmonic generation in the vicinity of metal nanostructures in noble gases

TL;DR

This paper develops a semiclassical model to understand how plasmonic nanostructures enhance high-harmonic generation in noble gases, revealing effects like even harmonic production and increased cutoff energies.

Contribution

It introduces a novel semiclassical approach that accounts for local field inhomogeneity and electron absorption, predicting significant enhancements in HHG efficiency near metal nanostructures.

Findings

Enhanced HHG with up to three orders of magnitude lower intensities

Generation of even harmonics due to field inhomogeneity

Cutoff energy more than doubled in nanostructure environments

Abstract

We present a semiclassical model for plasmon-enhanced high-harmonic generation (HHG) in the vicinity of metal nanostructures. We show that both the inhomogeneity of the enhanced local fields and electron absorption by the metal surface play an important role in the HHG process and lead to the generation of even harmonics and to a significantly increased cutoff. For the examples of silver-coated nanocones and bowtie antennas we predict that the required intensity reduces by up to three orders of magnitudes and the HHG cutoff increases by more than a factor of two. The study of the enhanced high-harmonic generation is connected with a finite-element simulation of the electric field enhancement due to the excitation of the plasmonic modes.