Raman Red-shift Compressor: A Simple Approach for Scaling the High Harmonic Generation Cut-off

High harmonic generation (HHG) in gasses has become a method of choice among table-top extreme ultraviolet (XUV) sources. In order to push the harmonic cut-off towards higher photon energies, many strategies can be implemented, including red-shifting and compressing the driver pulses. Here, we propose a new approach for tuning the red-shift of sub-picosecond driver pulses and compressing them to few-cycle durations in a single stage. This method uses newly discovered multidimensional solitary states (MDSS) pulses as a spatio-temporal engineered source based on the nonlinear Raman process in gas-filled hollow-core fibres (HCF) [1] . It has a few key advantages: 1) The MDSS pulses exhibit a negative quadratic spectral phase and can be compressed by simple propagation through glass. 2) In contrast with commonly-used optical parametric amplifiers, a small redshift can be obtained, allowing to reach a target XUV photon energy while minimizing the detrimental effects of long driver wavelengths on HHG efficiency. We apply our method to X-ray Resonant Magnetic Scattering (XRMS) measurements on a cobalt/platinum ferromagnet, an application that requires a high photon flux at the M 2,3 edge of cobalt (60 eV).