Abstract
Ultrafast strong-field physics provides insight into quantum phenomena that evolve on an attosecond time scale, the most fundamental of which is quantum tunneling. The tunneling process initiates a range of strong field phenomena such as high harmonic generation (HHG), laser-induced electron diffraction, double ionization and photoelectron holography—all evolving during a fraction of the optical cycle. Here we apply attosecond photoelectron holography as a method to resolve the temporal properties of the tunneling process. Adding a weak second harmonic (SH) field to a strong fundamental laser field enables us to reconstruct the ionization times of photoelectrons that play a role in the formation of a photoelectron hologram with attosecond precision. We decouple the contributions of the two arms of the hologram and resolve the subtle differences in their ionization times, separated by only a few tens of attoseconds.
Highlights
Ultrafast strong-field physics provides insight into quantum phenomena that evolve on an attosecond time scale, the most fundamental of which is quantum tunneling
Adding a weak perturbation modifies both the beam splitter, defining the relative strength of the signal and reference beams via control of the tunneling probability, and the length of each arm of the interferometer, via manipulation of the phase accumulated by the electron as it propagates in the continuum[20]
Phase perturbations, associated with subtle modifications of the propagation in the continuum, are manifested in a slight displacement of the holographic fringe pattern with the two-color delay, modulating the regions of constructive or destructive interference. Both the amplitude and phase perturbations are imprinted in the 3D holographic patterns that are formed during a two-color delay scan, and are measurable by their projection onto a 2D momentum detector
Summary
Ultrafast strong-field physics provides insight into quantum phenomena that evolve on an attosecond time scale, the most fundamental of which is quantum tunneling. Holography is induced by the interference of two electron trajectories, both driven by the strong laser field. Once the electron tunnel-ionizes, it is accelerated by the strong laser field, which dictates its final momentum.
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