a Controllable Diffraction Grating for Matter Waves

We report on the experimental realization of an atom optical device, that allows scanning and coherent splitting of an atomic beam. We used a time-modulated evanescent wave field above a glass surface to diffract a continuous beam of metastable neon atoms at grazing incidence. The diffraction angles and efficiencies were controlled by the frequency and form of the light intensity modulation, respectively. With an optimized shape, obtained from a numerical simulation, diffraction efficiencies into a single order of more than 50% were achieved.