Extracting an electron's angle of return from shifted interference patterns in macroscopic high-harmonic spectra of diatomic molecules

TL;DR

This paper demonstrates how the ellipticity of driving fields affects interference patterns in high-harmonic spectra from diatomic molecules, enabling extraction of an electron's angle of return through macroscopic measurements.

Contribution

It shows that the ellipticity-induced shift in interference patterns can be observed in macroscopic harmonic spectra, extending previous theoretical findings to experimental conditions.

Findings

Shift in interference maxima and minima due to ellipticity is observable in macroscopic spectra.

The shift persists in both near- and far-field regimes.

Parameter ranges for experimental observation are discussed.

Abstract

We investigate high-order harmonic spectra from aligned diatomic molecules in intense driving fields whose components have orthogonal polarizations. We focus on how the driving-field ellipticity influences structural interference patterns in a macroscopic medium. In a previous publication [Phys. Rev. A 88, 023404 (2013)] we have shown that the non-vanishing ellipticity introduces an effective dynamic shift in the angle for which the two-center interference maxima and minima occur, with regard to the existing condition for linearly polarized fields. In this work we show through simulation that it is still possible to observe this shift in harmonic spectra that have undergone macroscopic propagation, and discuss the parameter range for doing so. These features are investigated for $H_2$ in a bichromatic field composed of two orthogonally polarized waves. The shift is visible both in the near- and in the far-field regime, so that, in principle, it can be observed in experiments.