Generation of an optical ball bearing facilitated by coupling between handedness of polarization of light and helicity of its phase

We report on mutual transformation of spin and orbital angular momenta (SAM and OAM) of light upon tight focusing of circularly polarized vortex beams. In some regions of the focal spot, the OAM of light changes by a value ±2ℏ, while the circular polarization (CP) there reverses its rotation direction, resulting in adjacent rings (or core and adjacent ring) of opposite CP handedness. Moreover, the SAM has a transverse angular momentum (AM) component. We show that while the whole pattern rotates around the optical axis at the rate of the optical frequency divided by the value of total AM, the 3D SAM “balls” between adjacent rings (or between a ring and a core) spin in an opposite direction at the rate of the optical frequency, constituting an optical analog of a ball bearing. The applications include manipulation of particles, e.g., optical tweezers or spanners.