image: Schematic diagram of the light spin Hall effect driven by mixed spin-orbit coupling in organic microcavities. In the middle is the structure of the organic microcavity and the angle-resolved white light reflection spectra observed along two orthogonal directions. In the lower right corner is a schematic diagram of the spin patterns with different topological numbers observed in momentum space.
Credit: ©Science China Press
The research team achieved the hybrid spin-orbit coupling-driven optical spin Hall effect at room temperature for the first time through an organic microcavity structure. The device is a Fabry–Perot cavity built from a bottom distributed Bragg reflector and a thin silver top mirror, with a single-crystalline organic microbelt embedded inside. The organic crystal (TTPSB) is intrinsically anisotropic, helping introduce Rashba–Dresselhaus-type effects, while the cavity structure provides strong TE–TM splitting at larger angles.
At higher momenta, TE–TM splitting dominates, producing a quadrupole distribution of circular polarization: opposite circular polarizations occupy alternating quadrants. At lower momenta, Rashba–Dresselhaus-type coupling becomes prominent, yielding mirror-symmetric spin textures across the momentum map. Even more surprisingly, time-resolved measurements add an important practical point: the polarization can persist longer than the emission itself. While the microcavity emission lifetime is on the order of tens of picoseconds, the circular polarization lifetime extends to roughly 300 picoseconds at room temperature. This indicates a sustained spin (polarization) bias and robust spin coherence, both of which are desirable for polarization-preserving components and spin-photonic functionality on chip-scale platforms.
The significance of this achievement lies in selecting the corresponding momentum regions; the system effectively offers more than one “topological” spin texture within a single device, accessible by adjusting the momentum. This not only provides a new approach for developing room-temperature polarization-preserving optical chips and low-power quantum simulators, but also demonstrates the great potential of organic materials in integrated photonics. In the future, by optimizing the microcavity design, this technology is expected to be applied in high-speed information processing and quantum communication devices.