Polarization rotation of slow light with orbital angular momentum in ultracold atomic gases

Abstract

We consider the propagation of slow light with an orbital angular momentum (OAM) in a moving atomic medium. We have derived a general equation of motion and applied it in analyzing propagation of slow light with an OAM in a rotating medium, such as a vortex lattice. We have shown that the OAM of slow light manifests itself in a rotation of the polarization plane of linearly polarized light. To extract a pure rotational phase shift, we suggest to measure a difference in the angle of the polarization plane rotation by two consecutive light beams with opposite OAM. The differential angle {delta}{alpha}{sub l} is proportional to the rotation frequency of the medium {omega}{sub rot} and the winding number l of light, and is inversely proportional to the group velocity of light. For slow light the angle {delta}{alpha}{sub l} should be large enough to be detectable. The effect can be used as a tool for measuring the rotation frequency {omega}{sub rot} of the medium.