Comparison of two spatial characterisation methods of XUV high-order harmonics for spatio-temporal control of attosecond pulses
Résumé
Extreme ultraviolet (XUV) sources (10–100 nm) based upon high harmonic generation (HHG) in gases emit attosecond pulses and exhibit a high spatial and temporal coherence useful for a great range of applications. To further develop applications, it is very important to control the focusing of XUV beams as well as the evolution of the attosecond pulse duration during propagation. It has been demonstrated that the spatial profile of high harmonics strongly depends on the harmonic order [1] which consequently introduces chromatic aberrations at XUV focus and subsequent inhomogeneities in the attosecond temporal profile [2]. Nevertheless, the spatial properties of the XUV beam can be controlled to some extend [3], [4] in order to make it more homogeneous thus improving the spatio-temporal properties. To that respect retrieving the front phase of the XUV beam becomes essential. We will show two techniques to experimentally extract the front-phase.