Absorptive masks of light: A useful tool for spatial probing in atom optics

We demonstrate periodic localization of neutral atoms of better than 65 nm behind amplitude, i.e., absorptive masks made of light. With these masks, produced by a standing on resonant light wave, it is possible to create and to probe spatially well-defined atomic distributions. Applications of such absorptive masks range from atom lithography to fundamental atom optical experiments. As two examples we show how to use these gratings as a tool to measure the evolution of an atomic wave field behind a static Bragg crystal and its dependence on the incidence angle of the atomic beam and how to demonstrate the frequency shift of atoms diffracted at a modulated Bragg crystal in a beating experiment.