Generalized Brewster angle-enhanced photonic spin Hall effect in an all-dielectric metasurface.

The enhancement of the photonic spin Hall effect (PSHE) is usually limited at horizontally polarized incidence and around the nonadjustable Brewster angle. In this Letter, a flexible method for enhancing the reflective PSHE with tunable incident angle under both vertically (V) and horizontally (H) polarized light has been theoretically explored. By using the multipole decomposition method, the variable generalized Brewster angle (GBA) is proven to be obtained under both V- and H-polarized light at different wavelengths in the all-dielectric metasurface. Then, owing to the large ratio of Fresnel coefficients at the GBA, the enhancement of PSHE in this Letter can not only be available for both V- and H-polarization, but also achieved at widely tunable incident angle and different operating wavelengths in the same metasurface. This work provides a simple method to achieve the flexible enhancement of PSHE and offers a novel way for designing a functional spin-based photonic device.