Fig. 1: Schematic illustration of two-color attoclock interferometry.

a Common attoclock geometry constructed by multicycle 400 nm circular fields. The time-dependent rotating barriers formed by 400 nm circular fields are depicted. The time-to-angle mapping is given. b Measured PMD of strong-field ionization of Ar atoms on x–z polarization plane in 400 nm attoclock geometry. The emission angle θ is defined as the angle between the direction of the final momentum p and +z axis. c Temporal evolution of the two-color field configuration in the novel attoclock geometry, where a weak linearly polarized field at 800 nm along z direction is added to perturb the attoclock established by 400 nm circular fields. For times separated by one 400 nm optical cycle T₄₀₀, the perturbative 800 nm field points to opposite direction, thus leading to opposite modulation on the barrier, as depicted in the lower panel. Here, the barriers at times of t = 0 (T₄₀₀) and t = 0.25T₄₀₀ (1.25T₄₀₀) which correspond to the situations of θ = 270° and θ = 0°, respectively, are exemplified. They are manipulated by the fundamental field in parallel and perpendicular directions, respectively. The black lines show the unperturbed potential curves along z direction, while the red and blue dashed lines represent the oppositely modulated potential curves by the fundamental field at times separated by one 400 nm cycle. Varying the relative phase between two colors, the polarization configuration remains unchanged, whereas the perturbative field strength at the ionization time changes. d Measured two-color phase-integrated PMD on x–z polarization plane in two-color attoclock geometry.