The vortex-beam ‘precession’ in a rotating uniaxial crystal

Abstract

We consider theoretically and experimentally the precession of the optical vortex in a singular beam propagating nearly perpendicular to the crystal optical axis, the beam and the crystal axis rotating with different angular velocities. The precession is a result of anisotropic diffraction caused by different scales along the major axes in a uniaxial crystal. Also, we analyze the properties of an optical reducer consisting of two rotating crystals and a quarter-wave retarder between them, permitting us to control the form of the vortex trajectory and the angular velocity of the vortex beam.