Unidirectional propagation of surface plasmons under active control

Abstract

We proposed a symmetric V-type slit array to tune the propagation direction of surface plasmon polaritons by external control of the polarization and/or the inclination angle of the incident light. Using theoretical analysis and numerical simulation, we studied the position-related phase and spin-related phase of the SPPs excited by an inclined and circularly polarized light through a column of slits to determine the parameter of the structure. The results showed that we can tune the propagation of the SPPs with significant flexibility, by changing the polarization of the incident light and the inclination angle of the incident light. Furthermore, a nanostructures were designed to control directional launching of surface plasmons based on the principle of optical spin’s effect for the geometric phase of light. The propagation direction of the generated SPPs can be controlled by the spin of photons. The total size of the surface plasmon polariton (SPP) launcher is 320 nm by 180 nm, which is far smaller than the wavelength of the incident light. This result may provide a new way of spin-controlled directional launching of SPP.