Attosecond Pulse-shaping using a seeded free-electron laser

TL;DR

This paper demonstrates the first reproducible generation and shaping of high-energy attosecond pulses using a seeded free-electron laser, enabling advanced time-resolved experiments in ultrafast science.

Contribution

It introduces a novel method for amplitude and phase manipulation of attosecond waveforms using a seeded FEL, surpassing previous limitations of low efficiency and shot-to-shot variability.

Findings

Reproducible generation of high-energy attosecond pulses achieved.

Amplitude and phase control of attosecond waveforms demonstrated.

Potential for attosecond time-resolved experiments with FELs established.

Abstract

Attosecond pulses are fundamental for the investigation of valence and core-electron dynamics on their natural timescale. At present the reproducible generation and characterisation of attosecond waveforms has been demonstrated only through the process of high-order harmonic generation. Several methods for the shaping of attosecond waveforms have been proposed, including metallic filters, multilayer mirrors and manipulation of the driving field. However, none of these approaches allow for the flexible manipulation of the temporal characteristics of the attosecond waveforms, and they suffer from the low conversion efficiency of the high-order harmonic generation process. Free Electron Lasers, on the contrary, deliver femtosecond, extreme ultraviolet and X-ray pulses with energies ranging from tens of $\mathrm{\mu}$J to a few mJ. Recent experiments have shown that they can generate sub-fs spikes, but with temporal characteristics that change shot-to-shot. Here we show the first demonstration of reproducible generation of high energy ($\mathrm{\mu}$J level) attosecond waveforms using a seeded Free Electron Laser. We demonstrate amplitude and phase manipulation of the harmonic components of an attosecond pulse train in combination with a novel approach for its temporal reconstruction. The results presented here open the way to perform attosecond time-resolved experiments with Free Electron Lasers.