Polarization and ellipticity of high-order harmonics from aligned molecules generated by linearly polarized intense laser pulses

TL;DR

This paper presents theoretical calculations of the polarization and ellipticity of high-order harmonics from aligned molecules, revealing species-dependent polarization states that align well with experimental data.

Contribution

It introduces a rescattering model-based method to determine harmonic polarization amplitudes from photo-recombination amplitudes, enabling detailed polarization analysis of high-order harmonics.

Findings

Species-dependent polarization states confirmed

Excellent agreement with experimental polarization measurements

Polarization ellipse parameters facilitate complete molecular experiments

Abstract

We present theoretical calculations for polarization and ellipticity of high-order harmonics from aligned N$_2$, CO$_2$, and O$_2$ molecules generated by linearly polarized lasers. Within the rescattering model, the two polarization amplitudes of the harmonics are determined by the photo-recombination amplitudes for photons emitted parallel and perpendicular to the direction of the {\em same} returning electron wave packet. Our results show clear species-dependent polarization states, in excellent agreement with experiments. We further note that the measured polarization ellipse of the harmonic furnishes the needed parameters for a "complete" experiment in molecules.