Photonic spin-Hall effect at the nonparaxial focus of vortex beams

The spin-dependent transverse deflection of a light beam's trajectory, due to symmetry breaking of its intrinsic angular momentum structure, is known as the photonic spin Hall effect (PSHE). We propose and demonstrate an optical retroreflection scheme to measure the PSHE at the nonparaxial focus of linearly polarized vortex beam. Symmetry breaking due to the vortex phase structure leads to the PSHE even at the focal plane, which is measured in the far-field upon retroreflection by a multilayer dielectric mirror. Overall, the complex field components, with radial and azimuthal variation of the phase and polarization, results in polarization singularities, which directly relate to the PSHE. These spatially separated topological sub-wavelength markers will be useful in various metrological applications.