  The ability to control the spin-orbit interaction of light in optical
microresonators is of fundamental importance for future photonics. Organic
microcrystals, due to their giant optical anisotropy, play a crucial role in
spin-optics and topological photonics. Here we realize controllable and
wavelength-dependent Rashba-Dresselhaus spin-orbit interaction, attributed to
the anisotropic excitonic response in an optical microcavity filled with an
organic microcrystalline. We also investigate the transition of the spin-orbit
interaction from dominant photonic type caused by the splitting of the
transverse-electric and transverse-magnetic modes to spin-orbit interaction of
the Rashba-Dresselhaus type. The interplay of the two allows us to engineer the
spin-orbit interaction of light in organic microcavities, which besides its
fundamental interest promises applications in spin-controlled on-chip
integrated nanophotonic elements, towards exploiting non-magnetic and low-cost
spin-photonic devices.
