Monochromatization of femtosecond XUV light pulses with the use of reflection zone plates.

We report on a newly built laser-based tabletop setup which enables generation of femtosecond light pulses in the XUV range employing the process of high-order harmonic generation (HHG) in a gas medium. The spatial, spectral, and temporal characteristics of the XUV beam are presented. Monochromatization of XUV light with minimum temporal pulse distortion is the central issue of this work. Off-center reflection zone plates are shown to be advantageous when selection of a desired harmonic is carried out with the use of a single optical element. A cross correlation technique was applied to characterize the performance of the zone plates in the time domain. By using laser pulses of 25 fs length to pump the HHG process, a pulse duration of 45 fs for monochromatized harmonics was achieved in the present setup.