Temporal characterization of long quantum-path high harmonics

TL;DR

This study measures and characterizes the temporal profile of long-quantum path high harmonics in xenon, demonstrating pulses as short as 1.4 fs suitable for ultrafast EUV applications.

Contribution

First measurement of long-quantum path EUV high harmonic durations using a novel autocorrelation technique, enabling ultrashort pulse generation for nonlinear EUV experiments.

Findings

Long-quantum path harmonics have pulse durations as short as 1.4 fs.

Long trajectories produce sufficient flux for nonlinear EUV experiments.

Temporal resolution below 2 fs is achievable with long-path harmonics.

Abstract

We measure for the first time the duration of long-quantum path EUV high harmonics produced in xenon gas. The long-quantum path contribution to the high-harmonic signal was carefully controlled by employing a two-colour driving laser field and a high-harmonic spatial selection in the far field, over a range of $18-25\,eV$ in photon energy. To characterise the temporal profile of long quantum path high harmonics, we performed a second order volume autocorrelation ($2-IVAC$) via two EUV photon double ionization in argon. Our results show the production and characterisation of a train of EUV pulses from the long-path with pulse duration as short as $1.4\,fs$. This measurement demonstrates that the long-quantum path emission can have enough flux for performing non-linear EUV experiments, and that the long trajectories enable a pulse duration short enough to support measurements with a temporal resolution below $2\,fs$.