Incident-polarization-independent spin Hall effect of light reaching a half beam waist

TL;DR

This paper demonstrates a polarization-independent spin Hall effect of light at an interface where reflection coefficients are equalized, even for beams with a waist comparable to the wavelength, enabling new polarization-insensitive optical devices.

Contribution

It introduces a novel interface condition supporting polarization-independent spin Hall shifts for light beams with small waist sizes, expanding the applicability of spin Hall effect phenomena.

Findings

Spin Hall shifts are degenerate under any polarization.

The shift can reach half the beam waist under unpolarized light.

An isotropic-anisotropic interface supports polarization-independent shifts across all incident angles.

Abstract

The spin Hall effect of light, a spin-dependent transverse splitting of light at an optical interface, is intrinsically an incident-polarization-sensitive phenomenon. Recently, an approach to eliminate the polarization dependence by equalizing the reflection coefficients of two linear polarizations has been proposed, but is only valid when the beam waist is sufficiently larger than the wavelength. Here, we demonstrate that an interface, at which the reflection coefficients of the two linear polarizations are the same and so are their derivatives with respect to the incident angle, supports the polarization-independent spin Hall shift, even when the beam waist is comparable to the wavelength. In addition, an isotropic-anisotropic interface that exhibits the polarization-independent spin Hall shift over the entire range of incident angles is presented. Monte-Carlo simulations prove that spin Hall shifts are degenerate under any polarization and reaches a half of beam waist under unpolarized incidence. We suggest an application of the beam-waist-scale spin Hall effect of light as a tunable beam-splitting device that is responsive to the incident polarization. The spin Hall shift that is independent of the incident polarization at any incident angle will facilitate a wide range of applications including practical spin-dependent devices and active beam splitters.