High repetition rate high harmonic generation with ultra-high photon flux

High-harmonic generation (HHG) driven by ultrashort laser pulses is an established process for the generation of coherent extreme ultraviolet (XUV) to soft X-ray radiation, which has found widespread use in various applications [1] . In recent years photon-hungry applications such as coherent diffractive imaging [2] , [3] and applications based on statistical analysis [3] have required more powerful HHG sources, in particular, at high repetition rates. This need can be addressed by using high average power fiber lasers as the HHG drivers [4] . Here, we present a HHG-based XUV source, capable of providing a large photon flux across a wide range between 66 eV and 150 eV. It is driven by a commercial XUV beamline from Active Fiber Systems GmbH consisting of 100-W average power fiber-laser system, delivering up to 300 µJ at <300-fs pulse duration. For HHG this system is operated at 100 W, 600 kHz. A post-compression unit is part of the device to shorten the pulses to ~35 fs, the average power remains at 63W. The turnkey source can provide unprecedented photon fluxes of >10 11 photons/s in each harmonic between 69 eV and 75 eV (HH57-HH63). All fluxes are given at the generation point, i.e. directly after the source.