Optical spin-Hall effects in plasmonics

Abstract

Spin-Hall effect is a basic phenomenon arising from the spin-orbit coupling of electrons. In particular, the spatial trajectory of the moving electrons is affected by their intrinsic angular momentum. The optical spin-Hall effect (OSHE) - beam deflection due to the optical spin (polarization helicity) - was recently presented. The effect was attributed to the optical spin-orbit interaction occurring when the light passes through an anisotropic and inhomogeneous medium. Here, we present and experimentally observe the OSHE in coupled localized plasmonic chains. The OSHE is due to the interaction between the optical spin and the path of the plasmonic chain with an isotropic plasmonic mode. In addition, OSHE was observed due to the interaction between the optical spin and the local anisotropy plasmonic mode, which is independent on the chain path. A spin-dependent orbital angular momentum was observed in a circular path. Moreover, a wavefront phase dislocation due to the scattering of surface plasmons from a topological defect is directly measured in the near-field by means of interference. The dislocation strength is shown to be equal to the incident optical spin and with analogy to the magnetic flux parameter in the Aharonov-Bohm effect. OSHE in spontaneous emission was also obtained in a structure consisting of a coupled thermal antenna array. The effect is due to a spin-orbit interaction resulting from the dynamics of the surface waves propagating along the structure whose local anisotropy axis is rotated in space. The OSHE in the nanoscale provides an additional degree of freedom in spin-based optics.