# Reconstruction of attosecond pulses in the presence of interfering dressing fields using the 100 kHz ELI-ALPS HR-1 laser system

## TL;DR

This paper demonstrates the first high-repetition-rate (100 kHz) attosecond pulse measurements using a novel laser system, simplifying attosecond interferometry and expanding capabilities for ultrafast spectroscopy.

## Contribution

It introduces the first reconstruction of attosecond pulses at 100 kHz and shows the phase consistency of RABBIT measurements with an additional IR field, simplifying future experiments.

## Key findings

- First attosecond measurements at 100 kHz repetition rate.
- Phase of 2-omega beating matches standard RABBIT results.
- Experimental simplification for high-power laser-based attosecond interferometry.

## Abstract

Attosecond Pulse Trains (APT) generated by high-harmonic generation (HHG) of high-intensity near-infrared (IR) laser pulses have proven valuable for studying the electronic dynamics of atomic and molecular species. However, the high intensities required for high-photon-energy, high-flux HHG usually limit the class of adequate laser systems to repetition rates below 10~kHz. Here, APT's generated from the 100 kHz, 160 W, 40 fs laser system (HR1) of the Extreme Light Infrastructure Attosecond Light Pulse Source (ELI-ALPS) are reconstructed using the Reconstruction of Attosecond Beating By Interference of two-photon Transitions (RABBIT) technique. These experiments constitute the first attosecond time-resolved photoelectron spectroscopy measurements performed at 100 kHz repetition rate and the first attosecond experiments performed at ELI-ALPS. These RABBIT measurements were taken with an additional IR field temporally locked to the extreme-ultraviolet APT, resulting in an atypical omega beating. We show that the phase of the 2-omega beating recorded under these conditions is strictly identical to that observed in standard RABBIT measurements within second-order perturbation theory. This work highlights an experimental simplification for future experiments based on attosecond interferometry (or RABBIT), which is particularly useful when lasers with high average powers are used.