Near-circularly polarized attosecond pulse generation from nitrogen molecules in co-rotating two-color circularly polarized laser fields

We investigate theoretically the generation of a near-circularly polarized attosecond pulse from the N 2 molecules driven by co-rotating two-color circularly polarized (CTCP) laser fields by numerically solving the two-dimensional time-dependent Schrödinger equation. At the frequency ratio 3, the harmonics with large ellipticity can be obtained. Moreover, the intensity and ellipticity of the harmonics are not sensitive to the alignment angle of the N 2 molecules in CTCP laser fields. By adjusting the intensity ratio of CTCP laser fields with a frequency ratio of 3, an attosecond pulse with an ellipticity of 0.94 can be obtained.