  The tunnelling of an electron through a suppressed atomic potential followed
by its motion in the continuum, is the fundamental mechanism underlying
strong-field laser-atom/molecule interactions. Due to its quantum nature, the
interaction is governed by the phase of the released electron wave-packets.
Thus, detailed mapping of the electron wave-packet interferences provides
essential insight into the physics underlying the interaction. A process which
is providing access to the intricacies of the interaction is the generation of
high order harmonics of the laser frequency. The phase-amplitude distribution
of the emitted extreme-ultraviolet (EUV), carries the complete information
about the harmonic generation process and vice-versa. Thus, the visualization
of the EUV-spatial-amplitude-distribution, as it results from interfering
electron wave-packet contributions, is of crucial importance. Restrictions to
this accomplishment are due to the spatially integrating measurement approaches
applied so far, that average out the phase effects in the generation process.
In this work, we demonstrate a method which overcomes this obstacle. An
EUV-spatial-amplitude-distribution-image is induced from the imprint on the
measured spatial distribution of ions, produced through EUV-photon ionization
of atoms. Interference extremes in the image carry phase information about the
interfering electron wave-packets. The present approach provides detailed
insight on the strong-field laser-atom interaction mechanism, while
establishing the era of phase selective interaction studies. Furthermore, it
paves the way for substantial enhancement of the spectral and temporal
precision of measurements by in-situ controlling the phase distribution of the
emitted radiation and/or spatially selecting the EUV-radiation-atom interaction
products.
