Nanometer definition of atomic beams with masks of light

Efficient methods to prepare and measure atomic distributions with nanometer resolution are of particular interest in atom optics and for possible applications in science and technology. A versatile and particularly useful tool is absorptive masks, which can be used both to write and to probe fine structures. We combine the advantages of absorptive masks with the flexibility of light structures. We report the realization of well-defined absorptive masks at nanometer resolution for neutral atoms, which are entirely made of light.