Multiphoton ionization with three-dimensional light fields

We employ, for the first time, bichromatic three-dimensional (3D) polarization-shaped ultrashort laser fields in atomic multiphoton ionization to create previously inaccessible free-electron angular momentum wave packets. The 3D fields are created by the noncollinear superposition of two polarization-shaped pulses of different colors from a supercontinuum polarization pulse shaper and provide electric-field components along all spatial directions. The resulting photoelectron momentum distributions, recorded via velocity map imaging, demonstrate full 3D quantum control of electronic superposition states extending beyond the constraints of planar polarization fields by unlocking all dipole selection rules Δ m = 0 , ± 1 . As an application, 3D pump-probe fields are used to map spin-orbit dynamics of the potassium 3 d fine structure doublet. Our shaper-based approach establishes a route to fully controllable 3D light fields for chiral-sensitive light-matter interactions and ultrafast spectroscopy.