ИСТИНА

Here we present theoretical explanations of the observation [G. Lambert et al, Nature Comm., 6:6167 (2015)] of elliptically-polarized high harmonics as a result of interaction of two-color laser beams having orthogonal linear polarizations in a noble gas. Numerical calculations based on the non-perturbative light-atom interaction theory reproduce well the experimental data. In addition, the degree of polarization is analyzed for different harmonic orders and found to be high. Through a simplified theoretical model it is shown that the degree of harmonic ellipticity depends mainly on the population of atomic states sublevels with different angular momentum projections