A picosecond laser is used to realize atomic beam splitters based on stimulated Raman transitions. With this approach, the interaction between the laser and the atom is localized in the overlap zone of pairs of counterpropagating picosecond pulses. This imposes constraints for implementing interferometers on free-falling atoms. We have developed a robust technique to control the pulses' overlap and ensure that it follows the atom's trajectory while minimizing the induced laser phase noise. We also demonstrate an atom interferometer where the atomic beam splitters are applied to one arm of the interferometer without interacting with the atomic wave packet propagating along the other arm.