Polarization effects in two-colour ionization of hydrogen

In this work we analyse, via a perturbative calculation, the two-colour ionization of the hydrogen atom in its ground state by a coherent bichromatic laser field containing an UV laser and its third harmonic. We study the ionization process due to the net absorption of the energy 3ℎω. For the intensity domain in which the radiative corrections to the absorption of one harmonic photon can be neglected, the final continuum state is reached by the quantum interference of two pathways: (a) the absorption of one photon from the third harmonic, and (b) the absorption of three photons from the laser. For the two components of the electromagnetic field propagating in the same direction, we have investigated two different cases: i) identical elliptical polarizations, and ii) harmonic circularly polarized and laser linearly polarized. The influence of the light helicity on the azimuthal angular distribution are illustrated by graphs. The possibility to use this kind of scenarios in order to determine atomic phase differences is also considered. (authors)