Coupling of spin and angular momentum of light in plasmonic vortex.

We present that two distinct optical properties of light, the spin angular momentum (SAM) and the orbital angular momentum (OAM), can be coupled in the plasmonic vortex. If a plasmonic vortex lens (PVL) is illuminated by the helical vector beam (HVB) with the SAM and OAM, then those distinct angular momenta contribute to the generation of the plasmonic vortex together. The analytical model reveals that the total topological charge of the generated plasmonic vortex is given by a linear summation of those of the SAM and OAM, as well as the geometric charge of the PVL. The generation of the plasmonic vortex and the manipulation of the fractional topological charge are also presented.