Optical deflection and temporal characterization of an ultra-fast laser-produced electron beam*

The interaction of a laser-produced electron beam with an ultra-intense laser pulse in free space is studied. We show that the optical pulse with a$_{0}$=0.5 imparts momentum to the electron beam, causing it to deflect along the laser propagation direction. The observed 3-degree angular deflection is found to be independent of polarization and in good agreement with a theoretical model for the interaction of free electrons with a tightly focused gaussian pulse, but only when longitudinal fields are taken into account. This technique is used to temporally characterize a sub-picosecond laser-wakefield-driven electron bunch. Applications to modifying electron-beam properties (i.e., emittance, duration and energy spread) are also discussed.