Momentum domain polarization probing of forward and inverse spin Hall effect of leaky modes in plasmonic crystals

Simultaneous manifestation of both forward and inverse photonic Spin Hall effect in geometrically tailored anisotropic waveguided plasmonic crystal system is observed through the excitation of the leaky hybridized quasiguided modes. The quasiguided modes of the plasmonic crystal manifested in the far-field momentum (Fourier) domain as circular ring-like intensity distributions, and the different spin orbit interaction (SOI) effects revealed their exclusive signature as polarization-dependent azimuthal intensity lobes on top of it. Using a darkfield Fourier domain polarization Mueller matrix platform, we have observed input spin (circular polarization)- dependent trajectory of the leaky quasiguided modes in the momentum domain (forward spin Hall effect) and its reciprocal effect as the wave vector-controlled spin selection of quasiguided modes (inverse spin Hall effect). These effects are separately manifested in characteristic Mueller matrix elements enabling their interpretation as geometrical circular anisotropy effects. Resonance-enabled enhancement and control of these effects are also demonstrated by exploiting the spectral Fano-type resonance. The far-field manifestation of spin-directional excitation of leaky quasiguided modes, their unique interpretation through momentum domain Mueller matrix, regulation and control of the SOI effects in plasmonic-photonic crystal systems, opens up exciting avenues in spin-orbit photonic research.