Total Reflection-Induced Efficiency Enhancement of the Spin Hall Effect of Light

The spin Hall effect of light (SHEL) refers to the spin-dependent and transverse splitting of oblique incidence that occurs in both refraction and reflection. Enhancement of the SHEL is generally accompanied by a degradation in the efficiency. Recently, an anisotropic metamaterial has been proposed to attain a large SHEL with near-unity efficiency, but is limited to a horizontally polarized incidence. Here, a new approach to achieve a large SHEL and high efficiency simultaneously for arbitrarily polarized incidence is proposed by exploiting total external and internal reflection. The total reflection at the interface of a dense-to-sparse medium yields a theoretical maximum of the shift that is allowed for a unity efficiency. The SHEL can be further enhanced by increasing the refractive index contrast. Furthermore, we suggest a three-dimensional isotropic metamaterial that is designed to have an index below unity as a platform to experimentally demonstrate the SHEL with high efficiency. Our work will find wide applications in spin-dependent photonic devices.