Rewritable Binary Recording of the Photon Spin State in Chiral Liquid Crystals

We experimentally demonstrate that the spin state (up or down) of circularly polarized light can be reliably encoded as a polar structural state (up or down) in chiral liquid crystals, with high selectivity. This enables a spin-driven, nonvolatile binary liquid crystal memory, which can be optically written and electrically erased on demand. The underlying mechanism involves an orientational buckling instability, whose direction depends on whether the handedness of light matches or opposes that of the chiral medium. This optical poling effect arises from a chiral light-matter interaction during the propagation of light through the twisted anisotropic medium.