Quantum path interference in HHG: Impact on harmonic polarization and molecular imaging

Abstract

In high-order harmonic generation (HHG) from gases, two electronic quantum paths, the so-called "short" and "long" ones, are known to make the dominant contribution to the harmonics in the plateau. While the properties of the contributions from the individual quantum paths usually depend smoothly on the laser field parameters, the dependence of the total microscopic harmonic signal on them is complicated due to the interference of the different quantum paths. Our study shows that the above also holds for the polarization state of high-order harmonics, as well as for the multi-center interference patterns in the harmonic spectra frommolecules. It is therefore important to take care of an accurate selection of the contributions from the individual quantum paths in order to produce the XUV radiation with controllable polarization state or correctly extract an information about the molecular structure from the HHG spectra. © Springer-Verlag Berlin Heidelberg 2012.