Near-Field Observation of the Photonic Spin Hall Effect

The photonic spin Hall effect, referring to the spatial separation of photons with opposite spins due to spin–orbit interactions, has enabled potential for various spin-sensitive applications and devices. Here, using scattering-type near-field scanning optical microscopy, we observe spin–orbit interactions introduced by a subwavelength semiring antenna integrated in a plasmonic circuit. Clear evidence of unidirectional excitation of surface plasmon polaritons is obtained by direct comparison of the amplitude- and phase-resolved near-field maps of the plasmonic nanocircuit under excitation with photons of opposite spin states coupled to a plasmonic nanoantenna. We present details of the antenna design and experimental methods to investigate the spatial variation of complex electromagnetic fields in a spin-sensitive plasmonic circuit. The reported findings offer valuable insights into the generation, characterization, and application of the photonic spin Hall effect in photonic integrated circuits for future and emerging spin-selective nanophotonic systems.