Wide-angle giant photonic spin Hall effect

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The photonic spin Hall effect is a manifestation of the spin-orbit interaction of light and can be measured by a transverse shift $\ensuremath{\delta}$ of photons with opposite spins. The precise measurement of transverse shifts can enable many spin-related applications, such as precise metrology and optical sensing. However, this transverse shift is generally small (i.e., $\ensuremath{\delta}/\ensuremath{\lambda}<{10}^{\ensuremath{-}1}$, where $\ensuremath{\lambda}$ is the wavelength), which impedes its precise measurement. To date, proposals to generate a giant spin Hall effect (namely, with $\ensuremath{\delta}/\ensuremath{\lambda}>{10}^{2}$) have severe limitations, particularly its occurrence only over a narrow angular cone (with a width of $\mathrm{\ensuremath{\Delta}}\ensuremath{\theta}<{1}^{\ensuremath{\circ}}$). Here we propose a universal scheme to realize the wide-angle giant photonic spin Hall effect with $\mathrm{\ensuremath{\Delta}}\ensuremath{\theta}>{70}^{\ensuremath{\circ}}$ by exploiting the interface between free space and uniaxial epsilon-near-zero media. The underlying mechanism is ascribed to the almost-perfect polarization splitting between $s$ and $p$ polarized waves at the designed interface. Remarkably, this almost-perfect polarization splitting does not resort to the interference effect and is insensitive to the incident angle, which then gives rise to the wide-angle giant photonic spin Hall effect.