Single-shot Monitoring of Ultrafast Processes via X-ray Streaking at a Free Electron Laser

Michele Buzzi,Armin Kleibert,Boris Vodungbo,Jan Lüning,Christian David,Peter M Oppeneer,Pablo Maldonado,Harald Redlin,Nicolas Jaouen,Ludovic Howald,Kai Tiedtke,Jörg Raabe,Frithjof Nolting,Mikako Makita

doi:10.1038/s41598-017-07069-z

Abstract

The advent of x-ray free electron lasers has extended the unique capabilities of resonant x-ray spectroscopy techniques to ultrafast time scales. Here, we report on a novel experimental method that allows retrieving with a single x-ray pulse the time evolution of an ultrafast process, not only at a few discrete time delays, but continuously over an extended time window. We used a single x-ray pulse to resolve the laser-induced ultrafast demagnetisation dynamics in a thin cobalt film over a time window of about 1.6 ps with an excellent signal to noise ratio. From one representative single shot measurement we extract a spin relaxation time of (130 ± 30) fs with an average value, based on 193 single shot events of (113 ± 20) fs. These results are limited by the achieved experimental time resolution of 120 fs, and both values are in excellent agreement with previous results and theoretical modelling. More generally, this new experimental approach to ultrafast x-ray spectroscopy paves the way to the study of non-repetitive processes that cannot be investigated using traditional repetitive pump-probe schemes.

Highlights

To cite this version: Michele Buzzi, Mikako Makita, Ludovic Howald, Armin Kleibert, Boris Vodungbo, et al
With the advent of x-ray free electron lasers (XFELs), which produce extremely bright x-ray pulses as short as a few femtoseconds[1, 2], the potential of x-ray based techniques has been extended to investigations on ultrafast time scale
To demonstrate the capabilities of our novel x-ray streaking technique we investigated the ultrafast demagnetisation dynamics occurring in a thin ferromagnetic film upon non-thermal excitation by an intense, femtosecond short infrared pulse

Summary

Introduction

To cite this version: Michele Buzzi, Mikako Makita, Ludovic Howald, Armin Kleibert, Boris Vodungbo, et al. With the advent of x-ray free electron lasers (XFELs), which produce extremely bright x-ray pulses as short as a few femtoseconds[1, 2], the potential of x-ray based techniques has been extended to investigations on ultrafast time scale This allows shining light on phenomena that are difficult to study using optical spectroscopy, as for example distinguishing the individual dynamics of different components in complex materials[3,4,5,6]. Experiments resolving ultrafast processes rely on repetitive pump-probe techniques that do not allow probing of phenomena having a stochastic nature or systems that are difficult to reset repeatedly to the initial state To overcome these limitations, various methods based on spatial and spectral encoding of the pump-probe time delay have been developed in optical spectroscopy, which allow for time reconstruction of an ultrafast process from a single optical laser pulse[7,8,9]

Methods

Results

Conclusion