We have used a new technique to construct a clean, large-angle, coherent atomic beam splitter with an easily adjustable splitting angle. Helium atoms in the J=1 metastable state diffract from a far-detuned light field with ‘corkscrew’ polarization in the presence of a homogeneous magnetic field. Adiabatic transfer from magnetic energy to ‘transverse kinetic energy’ then allows symmetric diffraction of the incoming beam in a single, high diffraction order with a different value of M. The order is set by the value of the magnetic field. The result is a flexible, adjustable, large-angle, three-way atomic beam splitter for atom interferometry.
We report on a technique to split an atomic beam coherently with an easily adjustable splitting angle. In our experiment metastable helium atoms in the
∣1s2s3S1M=1⟩ state diffract from a polarization gradient light field formed by counterpropagating ${\ensuremath{\sigma}}^{+}$ and ${\ensuremath{\sigma}}^{\ensuremath{-}}$ polarized laser beams in the presence of a homogeneous magnetic field. In the near-adiabatic regime, energy conservation allows the resonant exchange between magnetic energy and kinetic energy. As a consequence, symmetric diffraction of
∣M=0⟩ or $|M=\ensuremath{-}1⟩$ atoms in a single order is achieved, where the order can be chosen freely by tuning the magnetic field. We present experimental results up to sixth-order diffraction ($24\ensuremath{\hbar}k$ momentum splitting, i.e., 2.21 m/s in transverse velocity) and present a simple theoretical model that stresses the similarity with conventional Bragg scattering. The resulting device constitutes a flexible, adjustable, large-angle, three-way coherent atomic beam splitter with many potential applications in atom optics and atom interferometry.