Femtosecond envelope of the high-harmonic emission from ablation plasmas

TL;DR

This paper measures the femtosecond temporal profile of high-harmonic emission from ablation plasmas, revealing that the emission closely follows the laser pulse duration, even in resonant conditions, which is important for developing high-flux XUV sources.

Contribution

It provides the first detailed temporal characterization of high-harmonic emission from various ablation plasmas, including resonant ones, showing the emission is directly driven by the laser pulse.

Findings

Harmonic emission durations are similar to or shorter than the driving laser pulse.

Emission is a directly laser-driven process even in resonant plasmas.

Results support the development of high-flux tabletop XUV sources.

Abstract

We characterize the temporal profile of the high-order harmonic emission from ablation plasma plumes using cross-correlations with the infrared (IR) laser beam provided by 2-photon harmonic+IR ionization of rare gas atoms. We study both non-resonant plasmas (lead, gold and chrome) and resonant plasmas (indium and tin), i.e. plasmas presenting in the singly-charged ions a strong radiative transition coinciding with an harmonic order. The cross-correlation traces are found very similar for all harmonic orders and all plasma targets. The recovered harmonic pulse durations are very similar to the driving laser, with a tendency towards being shorter, demonstrating that the emission is a \stef{directly} laser-driven process even in the case of resonant harmonics. This provides valuable input for theories describing resonant harmonic emission and opens the perspective of a very-high-flux tabletop \textsc{xuv} source for applications.