Elliptically polarized high-order harmonics from mixed gases by a combined laser field

We theoretically investigate the elliptically polarized (EP) high-order harmonic generation (HHG) from the mixed gases driven by the combined laser field, which is combined with an EP laser field and a linearly polarized (LP) laser field. The numerical results show that the harmonic intensity is enhanced, and the cutoff is extended compared with that in the EP laser field. Benefiting from the interference between the harmonics generated from the two single gases, we obtain the bright broadband EP HHG with large ellipticity from the mixed gases. The origin of the harmonic ellipticity is illustrated by the trajectories of the electrons. The result indicates that the harmonic ellipticity is large if the angle between the velocity directions at the initial time and the final time is close to 90°. In addition, the analysis shows that the left-handed components of the harmonics from two single gases produce destructive interference, and the right-handed components of that produce constructive interference, which results in the enhancement of the intensity difference of the left- and right-handed harmonics from the mixed gases. Thus, the harmonic ellipticity is large from the mixed gases. Our results are conducive to obtaining near circularly polarized (CP) XUV and attosecond pulse radiation from mixed gases in a broad spectral range.