Generation of elliptically polarized attosecond pulses in mixed gases

We propose and theoretically demonstrate a scheme to generate elliptically polarized attosecond pulses with mixed gases. As the harmonic radiations from different gases with opposite orbital parity interfere destructively for one helicity component and constructively for the other, the high-order harmonics from the mixture exhibit large ellipticity with the same helicity in a wide spectral range. Hence, highly elliptically polarized attosecond pulses can be generated from the mixed gases and the ellipticity can be tuned by controlling the mixing ratio and the molecular alignment angle. Furthermore, this interference effect is only related to the features of the mixed gases such as the structure and orbital symmetry of the molecules and atoms. The polarization control is independent of the temporal profile manipulation of the attosecond pulses by shaping the driving field. Consequently, our work paves an effective and convenient way to produce elliptically polarized isolated attosecond pulses with mixed gases by optimizing the polarization and temporal profile individually.