Optical Metasurface for the Creation and Applications of Surface Plasmon Vortices

Abstract

Optical vortices are waves carrying orbital angular momentum and exhibit helical phase fronts. Helical phase front leads to discontinuous azimuthal phase jumps and the number of phase discontinuities (abrupt phase jumps from −π to π) within a 2π range is referred to as the topological charge of an optical vortex. Optical vortices have been applied in trapping and spinning of microparticles, and recently in free-space data transmission. Generation of optical beams carrying orbital angular momentum has received increasing attentions recently, both in the far-field and in the near-field. Near-field vortices are typically generated through the excitation of surface plasmons (SP). However, the intensity patterns of the SP vortices generated thus far, just like the free-space vortex beams, are all azimuthally symmetrical (annular) since mathematically they conform to the Bessel function.