High-purity free-electron momentum states prepared by three-dimensional optical phase modulation

The generation of high-coherence, ultrashort electron pulses, and their manipulation by intense light fields promises new pathways in the active control of free-electron beams. Harnessing the temporal coherence, a broad range of applications was explored, from efficient free-space acceleration to attosecond bunching of electrons. Elastic diffraction at the ponderomotive optical potential enabled the observation of the Kapitza-Dirac effect [1] and the recent implementation of a Zernicke phase plate [2] . However, precise optical phase control of free-electron wave packets in space and time remains challenging.