Enhancing angular photonic spin Hall effect at surface plasmon resonance.

The photonic spin Hall effect (PSHE) is the deep subwavelength spin component shift of light induced by the spin-orbit interaction of photons. Here, we demonstrate a polarimetric scheme to directly measure the surface plasmon resonance-enhanced angular PSHE in the Kretschmann configuration using a gold film. In contrast to the weak measurement scheme that indirectly measures the spatial term-dominated PSHE using a well-collimated source, we focused the incident beam to a small beam waist and significantly enhanced the angular PSHE. Imbert-Fedorov shift manifested as a displacement offset of the reflected beam, have been taken into account to extract only the PSHE shift. In practical measurements, accounting for this shift enables accurate separation of PSHE from polarization-induced artifacts. Measuring PSHE provides an additional spin degree of freedom, enabling an innovative approach toward spin-controlled nanophotonic applications, including optical sensing, precision metrology, and high-contrast microscopy.