Ultrafast dynamics of Argon single ionization driven by two‑color laser fields

The photoelectron momentum distribution resulting from the single ionization of atoms driven by two-color laser fields was investigated. By adjusting the crossing angle and relative phase of the two-color fields， the effective control over the emission direction of photoelectrons was achieved. Experimentally， photoelectron momentum distributions were measured using a cold target recoil ion momentum spectroscopy （cold target recoil ion momentum spectroscopy （COLTRIMS）） setup under linearly polarized 800 nm + 400 nm two-color laser fields with varying crossing angles and relative phases. The results showed that， with increasing crossing angle， the principal axis of the momentum distribution tilted， the tilt angle was approximately equal to half of the crossing angle. Moreover， periodic oscillations in the momentum distribution between the second and fourth quadrants were observed as the relative phase varied. Theoretically， a classical ensemble model incorporating the Heisenberg potential was employed to simulate the experimental results， revealing relationships between the emission direction of photoelectrons and the ionization time delay. It was found that increasing the crossing angle confined electron emission to within a single optical cycle， and that intracycle interference significantly altered photoelectron trajectories. These combined experimental and theoretical findings demonstrated that both the crossing angle and relative phase of the two-color fields could be used synergistically to precisely control the angular distribution and symmetry of photoelectron emission.