Controllable photonic spin Hall effect induced by an off-axis polarization singularity

The photonic spin Hall effect (PSHE) with high efficiency is of significance for the application of spin photonic devices, but the spin-dependent separation induced by the refraction or reflection at the interface of the media is too tiny to be used in practice. In this paper, we realize a PSHE by designing off-axis polarization singularity in free space and reveal the relationship between controllable spin-orbit coupling and orbital angular momentum (OAM) spectra of the off-axis vector beam. The numerical simulations and experimental results show that the spin-dependent separated distance and the OAM spectra are manipulated by the embedded position and polarization order of polarization singularity, and the separating direction perpendicular to the off-axis direction of polarization singularity. Our work provides a feasible and simple path for manipulating spin photons toward information processing based on optical spintronics.