Vector beam generation based on the nanometer-scale rectangular holes

A kind of plasmonic vector beam generator is proposed with the help of a compact nano-hole structure. The structure is composed of the homogeneous rectangular holes which are etched in a silver film and arranged in an Archimedes' spiral. Under the circularly polarized light illumination, each rectangular hole is identified as a quarter-wave plate, and the vector beams including the radial and azimuthal polarization beams can form through properly orientating and spirally arranging these holes. The numerical simulations according to the finite-difference time-domain method provide the parameters of the optimized structure of the vector beam generator. The theoretical analysis reveals the formation principle of the vector beams. The practical measurement for the diffraction of the proposed structure verifies the vector beam generation. (C) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement