Towards the complete phase profiling of attosecond wave packets

Realistic attosecond wave packets have complex profiles that, in dispersive conditions, rapidly broaden or split in multiple components. Such behaviors are encoded in sharp features of the wave packet spectral phase. In a combined theoretical and experimental work on attosecond photoionization of helium [1], we use the energy-resolved quantum beating between one- and two-photon transitions to reconstruct sharp features of the spectral phase, as a continuum function of energy across the full spectral range of an attosecond pulse train. We demonstrate that this scheme can be used to observe the periodic modulations of the spectral phase of an attosecond pulse train due to the individual chirp of each harmonic.

[1] J. Fuchs et al. Phys. Rev. Research 3, 013195 (2021)