Tailoring high-order harmonic generation with nonhomogeneous fields and electron confinement

TL;DR

This paper investigates how nonhomogeneous fields and electron confinement in plasmonic nanostructures enhance high-order harmonic generation, extending the harmonic cutoff and improving XUV source potential.

Contribution

It combines TDSE simulations with 3D finite element electric field modeling to analyze the effects of field inhomogeneity and electron confinement on HHG.

Findings

Inhomogeneous fields significantly extend the harmonic cutoff.

Electron confinement enhances HHG efficiency.

Time-frequency analysis reveals detailed spectral features.

Abstract

We study high-order harmonic generation (HHG) resulting from the illumination of plasmonic nanostructures with a short laser pulse. We show that both the inhomogeneities of the local electric field and the confinement of the electron motion play an important role in the HHG process and lead to a significant increase of the harmonic cutoff. In order to understand and characterize this feature, we combine the numerical solution of the time dependent Schroedinger equation (TDSE) with the electric fields obtained from 3D finite element simulations. We employ time-frequency analysis to extract more detailed information from the TDSE results and to explain the extended harmonic spectra. Our findings have the potential to boost up the utilization of HHG as coherent extreme ultraviolet (XUV) sources.