Spin-Controlled Directional Launching of Surface Plasmons Under Oblique Illumination

We proposed a scheme to tune the propagation direction of surface plasmon polaritons (SPPs) by external control of the polarization and/or the inclination angle of the incident light. The phase of the SPPs generated by the laser beam through slits can be divided into two parts: the position-related phase which is affected by the position of slits and spin-related phase which is affected by the orientation of slits and spin of photons. 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 and then designed symmetric V-type slit array. We found when the incident light is in the symmetry plane of symmetric V-type slit array, spin of the incident light would give directions of surface plasmon propagation and the inclination angle of the incident light would give the inclination angle of surface plasmon propagation. The result shows that we may 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. Our designed launcher, as a spin plasmonic device under control, is expected to be of interest for future applications in photonic integrated circuits.