Generation of Ultrafast Laser Pulses at the SXP Instrument of the European XFEL

At the European X-ray Free Electron Laser (XFEL) facility a new instrument, the Soft X-ray Port (SXP), is currently under commissioning [1]. It is primarily designed for time- and spin-resolved X-ray photo-electron spectroscopy (TR-XPES), but investigations of complex chemical and bio-inorganic molecular systems with fluorescence spectroscopy as well as research on highly charged ions are also envisioned [2]. SXP is located downstream of the SASE 3 soft X-ray undulator system providing ultrafast photon pulses with variable polarization in the energy range between 260 eV and 3000 eV, at MHz repetition rates. Up to $10^{12}$ photons per pulse will be focus at the interaction region in a micrometer spot size resulting in an intensity of more than $10^{18}\mathrm{W}/\text{cm}^{2}$ . These outstanding specifications will enable the complete electronic, chemical and atomic characterization of solids, surfaces and interfaces using TR-XPES. For this purpose, two powerful pump-probe lasers operating in a broad spectral range from the mid-infrared to the ultraviolet region will be available. Herriott-type multi pass cells (MPC) will be used to compress their pulses into the few femtosecond range paving the way for ultrafast time-resolved investigations at the SXP instrument combining intense and tunable soft X-rays with versatile optical laser capabilities. Fig. 1 On the left, typical laser spectra before and after passing the herriott multi pass cell. On the right, autocorrelation measurements of the original and compressed laser pulses showing a reduction in pulse lengths from 300 fs to about 30 fs.