  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.
