High-order harmonic generation driven by inhomogeneous plasmonics fields spatially bounded: influence on the cut-off law

TL;DR

This paper investigates how spatially inhomogeneous plasmonic fields influence high-order harmonic generation, revealing a novel wavelength-cutoff relationship and enabling improved control of HHG processes through detailed field modeling.

Contribution

It introduces a precise modeling approach for inhomogeneous plasmonic fields and demonstrates their significant impact on HHG cutoff laws, advancing understanding of plasmonic-enhanced HHG.

Findings

Inhomogeneous fields alter the HHG cutoff-wavelength relationship.

Accurate field modeling predicts the extended HHG spectra.

Classical and quantum simulations agree on trajectory-based HHG characteristics.

Abstract

We study high-order harmonic generation (HHG) in model atoms driven by plasmonic-enhanced fields. These fields result from the illumination of plasmonic nanostructures by few-cycle laser pulses. We demonstrate that the spatial inhomogeneous character of the laser electric field, in a form of Gaussian-shaped functions, leads to an unexpected relationship between the HHG cutoff and the laser wavelength. Precise description of the spatial form of the plasmonic-enhanced field allows us to predict this relationship. We combine the numerical solutions of the time-dependent Schr\"odinger equation (TDSE) with the plasmonic-enhanced electric fields obtained from 3D finite element simulations. We additionally employ classical simulations to supplement the TDSE outcomes and characterize the extended HHG spectra by means of their associated electron trajectories. A proper definition of the spatially inhomogeneous laser electric field is instrumental to accurately describe the underlying physics of HHG driven by plasmonic-enhanced fields. This characterization opens new perspectives for HHG control with various experimental nano-setups