Interference effect in high-order harmonic generation from degenerate current-carrying orbitals of polyatomic molecules

When the molecules with degenerate current-carrying orbitals are exposed to the bichromatic counterrotating circularly polarized (BCCP) laser fields, the destructive interference between high harmonics from these orbitals results in a strong suppression of harmonic emission with the selected helicity. As a result, there are large intensity differences between the high harmonics with opposite helicities in a wide spectral range. This interference effect is related to the noncylindrical symmetry of the molecular current-carrying orbitals and therefore depends on the relative orientation between the molecule and the driving laser fields. Furthermore, our results show that this interference can be controlled by adjusting the relative intensity ratio of the BCCP field. Finally, we show that highly elliptically polarized attosecond pulses can be generated by using this interference and their ellipticities can be tuned by controlling the molecular orientation.