Estimating the plasmonic field enhancement using high-order harmonic generation: The role of inhomogeneity of the fields

TL;DR

This paper investigates how the spatial inhomogeneity of plasmonic fields affects the estimation of laser intensity from high-order harmonic generation, proposing improved methods for accurate intensity measurement in nanostructures.

Contribution

It introduces a revised approach to estimate laser intensity considering field inhomogeneity, validated through quantum and classical calculations.

Findings

Inhomogeneity significantly alters harmonic cutoff estimates.

Revised methods improve accuracy of intensity estimation in plasmonic fields.

Quantum and classical models agree on the importance of field inhomogeneity.

Abstract

In strong field laser physics it is a common practice to use the high-order harmonic cutoff to estimate the laser intensity of the pulse that generates the harmonic radiation. Based on the semiclassical arguments it is possible to find a direct relationship between the maximum value of the photon energy and the laser intensity. This approach is only valid if the electric field driving HHG is spatially homogenous. In laser-matter processes driven by plasmonics fields, the enhanced fields present a spatial dependence that strongly modifies the electron motion and consequently the laser driven phenomena. As a result, this method should be revised in order to more realistically estimate the field. In this work, we demonstrate how the inhomogeneity of the fields will effect this estimation. Furthermore, by employing both quantum mechanical and classical calculations, we show how one can obtain a better estimation for the intensity of the enhanced field in plasmonic nanostructure.