Estimating the plasmonic field enhancement using high-order harmonic generation: the role of the 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 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 laser electric field driving the high-order harmonic radiation is spatially homogeneous. In laser–matter processes driven by plasmonics fields, the enhanced fields present a spatial dependence that strongly modifies the electron motion and consequently all the associated laser driven phenomena. As a result, this method should be revised in order to more realistically estimate the intensity of the laser field. In this work, we demonstrate how the inhomogeneity of the enhanced plasmonic fields will affect 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 nanostructures.