Generating a plasmonic vortex field with arbitrary topological charges and positions by meta-nanoslits.

A novel plasmonic vortex lens (PVL) consisting of an array of gold film nanoslits for vortex-field generation with arbitrary topological charges and positions is proposed. The performance of the PVL is analyzed theoretically and demonstrated numerically by the finite-element method. By utilizing a symmetric and antisymmetric phase, the plasmonic vortex generated at the center of the PVL can carry arbitrary topological charges (integer or fraction). Two circularly polarized illuminations with opposite spins can excite a composite plasmonic vortex field with symmetry-breaking distribution, in which the breaking point rotates with the phase difference between two spins. In addition, we can shift the center of the plasmonic vortex to any desired position such that a flexible location manipulation of the plasmonic vortex is achieved. The designed PVL can also work as a miniaturized polarimeter for characterizing the state of polarization of the incident light.