The directional excitation of surface plasmon polaritons by radially polarized beam with multiple off-axis vortices

Abstract

A method of directional excitation of surface plasmon polaritons (SPPs) is proposed by using radially polarized beam loaded with multiple off-axis vortices. Based on the Kretschmann–Raether three-layer structure, the theory expression for the distribution of SPPs on the silver film surface excited by the radially polarized beam loaded with multiple off-axis vortices is derived. Accordingly, the influence of multiple off-axis vortices on the distribution of focus field and SPPs is analyzed, in which the asymmetry of the SPPs caused by the off-axis vortex is found out. On this basis, the SPPs are directionally excited by adjusting the arrangement and position of multiple off-axis vortices reasonably. This work demonstrated that the off-axis vortices introduce a new degree of freedom for SPPs manipulation, and that the excitation and propagation of SPPs can be dynamically controlled by judiciously arranging the multiple off-axis vortices. Without specially designed metal structures, the all-optical controlled method for SPPs manipulation has great potential in plasmonic tweezers and plasmonic devices.