%0 Journal Article %T Origin of ellipticity of high-order harmonics generated by a two-color laser field in the cross-polarized configuration %+ Faculty of Physics [MSU, Moscow] %+ Laboratoire d'optique appliquée (LOA) %+ Sorbonne Université (SU) %+ Laboratoire de Chimie Physique - Matière et Rayonnement (LCPMR) %+ Laboratoire Interactions, Dynamiques et Lasers (ex SPAM) (LIDyl) %+ Attophysique (ATTO) %A Stremoukhov, S. %A Andreev, A. %A Vodungbo, Boris %A Salières, P. %A Mahieu, B. %A Lambert, Guillaume %< avec comité de lecture %@ 1050-2947 %J Physical Review A : Atomic, molecular, and optical physics [1990-2015] %I American Physical Society %V 94 %P 013855 %8 2016-07-29 %D 2016 %R 10.1103/PhysRevA.94.013855 %Z Physics [physics]Journal articles %X Recently several techniques demonstrated the production of elliptically polarized high harmonics. One of these techniques consists of the interaction in a noble gas of two-color laser beams having orthogonal linear polarizations. Here we present the theoretical explanation of such a result observed in Lambert et al. [Nat. Commun. 6, 6167 (2015)]. Numerical calculations based on the nonperturbative light-atom interaction theory reproduce well the experimental data. The degree of polarization is analyzed for different harmonic orders and found to be high. With the help of a simplified theoretical model it is shown that the degree of harmonic ellipticity depends mainly on the population of atomic state sublevels with different angular momentum projections. %G English %L cea-01426406 %U https://cea.hal.science/cea-01426406 %~ CEA %~ X %~ UPMC %~ ENSTA %~ CNRS %~ X-LOA %~ X-DEP %~ X-DEP-PHYS %~ LCPMR %~ ENSTA_LOA %~ INC-CNRS %~ IRAMIS-LIDYL %~ CEA-UPSAY %~ UNIV-PARIS-SACLAY %~ CEA-UPSAY-SACLAY %~ X-SACLAY %~ ENSTA-SACLAY %~ UPMC_POLE_2 %~ SORBONNE-UNIVERSITE %~ SU-INF-2018 %~ SU-SCIENCES %~ GS-ENGINEERING %~ IRAMIS %~ GS-CHIMIE %~ GS-PHYSIQUE %~ INSTITUT-SCIENCES-LUMIERE %~ ALLIANCE-SU %~ TEST2-HALCNRS %~ CHIMIE-SU