Large-angle adjustable coherent atomic beam splitter by Bragg scattering

Abstract

Using a ``monochromatic'' (single-axial-velocity) and slow (250 m/s) beam of metastable helium atoms, we realize up to eighth-order Bragg scattering and obtain a splitting angle of 6 mrad at low laser power (3 mW). This corresponds to a truly macroscopic separation of 12 mm on the detector. For fifth-order scattering, we have observed several oscillations of the splitting ratio when varying the laser power (``Pendell\"osung oscillations''). The large splitting angle, the adjustable splitting ratio, and the cleanness of the split beams, with $200\ensuremath{-}\ensuremath{\mu}\mathrm{m}$ rms width each, make the beam splitter ideal for a large-enclosed-area atom interferometer.