A synchronized VUV light source based on high-order harmonic generation at FLASH

Elisa Appi,Skirmantas Ališauskas,Maciej Brachmanski,Markus Braune,Christoph Jusko,Florian Trost,R Treusch ,R Moshammer ,Philip Mosel,Ingmar Hartl,Tino Lang,Patrizia Schoch,Bastian Manschwetus,Jose Mapa ,Christina Papadopoulou ,Uwe Morgner,Christoph M Heyl,Severin Meister,Nishad Wesavkar,Hannes Lindenblatt ,Milutin Kovačev

doi:10.1038/s41598-020-63019-2

Abstract

Ultrafast measurements in the extreme ultraviolet (XUV) spectral region targeting femtosecond timescales rely until today on two complementary XUV laser sources: free electron lasers (FELs) and high-harmonic generation (HHG) based sources. The combination of these two source types was until recently not realized. The complementary properties of both sources including broad bandwidth, high pulse energy, narrowband tunability and femtosecond timing, open new opportunities for two-color pump-probe studies. Here we show first results from the commissioning of a high-harmonic beamline that is fully synchronized with the free-electron laser FLASH, installed at beamline FL26 with permanent end-station including a reaction microscope (REMI). An optical parametric amplifier synchronized with the FEL burst mode drives the HHG process. First commissioning tests including electron momentum measurements using REMI, demonstrate long-term stability of the HHG source over more than 14 hours. This realization of the combination of these light sources will open new opportunities for time-resolved studies targeting different science cases including core-level ionization dynamics or the electron dynamics during the transformation of a molecule within a chemical reaction probed on femtosecond timescales in the ultraviolet to soft X-ray spectral region.

Highlights

Ultrafast measurements in the extreme ultraviolet (XUV) spectral region targeting femtosecond timescales rely until today on two complementary XUV laser sources: free electron lasers (FELs) and high-harmonic generation (HHG) based sources
Our initial goals include the observation of harmonics with the present approach and the measurement of their basic parameters such as photon flux and spectral coverage, in order to evaluate the performance of such a VUV source directly at a FEL beamline
We demonstrated the first realization of a permanent VUV beamline installed as pump-probe source at a free-electron laser

Summary

Introduction

Ultrafast measurements in the extreme ultraviolet (XUV) spectral region targeting femtosecond timescales rely until today on two complementary XUV laser sources: free electron lasers (FELs) and high-harmonic generation (HHG) based sources. First commissioning tests including electron momentum measurements using REMI, demonstrate long-term stability of the HHG source over more than 14 hours This realization of the combination of these light sources will open new opportunities for time-resolved studies targeting different science cases including core-level ionization dynamics or the electron dynamics during the transformation of a molecule within a chemical reaction probed on femtosecond timescales in the ultraviolet to soft X-ray spectral region. The HHG source provides much broader spectral bandwidth than the FEL, which is beneficial for transient absorption experiments to cover multiple spectral resonances within one acquisition This way, the combination of two powerful extreme ultraviolet femtosecond sources, FELs and HHG-based sources, can enable VUV-XUV pump-probe experiments, which are ideally suited for studying time-resolved light-matter interaction of small quantum systems after VUV excitation and/ or ionization. The VUV source is characterized and employed for first proof-of-principle studies enabling the production and detection of Ar+ ions inside REMI, demonstrating the capability of this source for future VUV-XUV pump-probe studies

Methods

Results

Conclusion