Organic Alloy Crystal Microcavity Boosting the Controllable Photonic Spin–Orbit Coupling

The optical spin–orbit coupling (SOC) provides a route to manipulate the polarization degrees of freedom of photons for multidimensional encoding and information processing. Here, we demonstrate tunable optical SOC in anisotropic organic alloy crystal-filled microcavities. By adjusting the proportion of the host and guest molecules, the anisotropy of the organic alloys can be designed on-demand, which directly determines the energy splitting of different spins (σ+/σ– circular polarization) that is associated with the coupling strength of the optical SOC in such microcavities. The experimental results also reveal the relationship between the strength of the SOC and the index difference of the perpendicularly linearly polarized cavity modes with opposite parity. Our work provides a desired platform for in-depth investigation of the controllable SOC, which shows promising potential in integrated photonic chips and photonic emulators.