Directive surface wave on nanoplasmonic film: the roles of photonic spin-Hall effect and optical interactions

Abstract

Interaction of the spin and orbital angular momentum of light, occurring in the photonic spin Hall effect (PSHE), leads to the separation of photons with opposite spins (two different forms of circularly polarized wave) toward opposite directions perpendicular to the pump light-beam path. As photons with two opposite spins illuminate a nanoparticle (NP) near a metal–dielectric interface (MDI), the associated evanescent fields excite spin-dependent directional surface plasmon polaritons (SPPs) with transverse spins. We show that a circularly polarized incident optical beam, which contains only one spin state, causes the directional scattering of SPPs on the nanoplasmonic-film surface, following the PSHE. Here, Green’s tensor approach in conjunction with the mode-matching technique are developed and employed to describe this effect. Based on quasi-static modeling, the effects of crucial parameters on the directive propagating of the confined surface wave and on its corresponding directional pattern are theoretically and numerically studied. Interestingly, the theoretical results, adequately confirmed by the computations, demonstrate that an excited plasmonic NP with a little horizontal elongation to modify internal electric polarization of the NP remarkably enhances the PSHE, resulting in almost unidirectional scattering of the launched SPP on the MDI. The findings pave a way for SPP-based engineering applications and multichannel photonic communications.