Interference carpets in above-threshold ionization: from the Coulomb-free to the Coulomb-dominated regime.

The velocity map recorded in above-threshold ionization of xenon at 800 nm exhibits a distinct carpetlike pattern of maxima and minima for emission in the direction approximately perpendicular to the laser polarization. The pattern is well reproduced by a numerical solution of the time-dependent Schrödinger equation. In terms of the simple-man model and the strong-field approximation, it is explained by the constructive and destructive interference of the contribution of the long and the short orbit. Strictly perpendicular emission is caused by ionization at the two peaks of the laser field per cycle, which results in a 2hω separation of the above-threshold ionization rings.

Two-dimensional streaking: complete characterization of an arbitrarily polarized few-cycle laser pulse using a stereodetector technique.

We discuss the feasibility of measuring the temporal variation of the electric-field strength of a few-cycle laser pulse with arbitrary polarization using the attosecond streaking method. It is shown that a full characterization of the field requires measuring the photoelectron momenta in two opposite directions in the laser polarization plane for various delays of the extreme ultraviolet burst with respect to the probed laser pulse.

Laser-induced recollision phenomena: interference resonances at channel closings.

An analytical theory of the resonancelike phenomena in high-order above-threshold ionization is presented that explains details of the experimental spectra and theoretical simulations. It traces the observed features to the constructive interference of "quantum orbits" with long travel times at laser intensities where the N-photon ionization channels close. Characteristic differences show up between even and odd N. The effects are generic to all laser-induced recollision phenomena. For nonsequential double ionization, their signature in the momentum distribution of the final electrons is identified.

Coulomb asymmetry in above-threshold ionization.

A new method for including effects of the Coulomb potential in strong-field laser atom interaction is presented. The model is tested by comparing its results with experimental data of energy resolved angular distributions of photoelectrons. For elliptical polarization these exhibit a strong asymmetry. Our theory shows that this strong asymmetry for the low-energy electrons is induced by a small Coulomb force acting on the tunneling electron just after the exit of the tunnel. This is in contrast to the situation for high electron energies where the asymmetry arises via rescattering by the parent ion.