Photoalignment effect induced by angular momentum of light in dye-doped liquid crystals

We studied the effective interaction of the angular momentum of light with a liquid crystal (LC) doped with azo-dye. The experiments were carried out in a combined cell with one substrate providing strong unidirectional planar alignment of LC and the other covered by isotropic polymer layer providing a degenerated planar alignment. The effect manifests itself as azimuth reorientation of the liquid crystal director under the action of circularly polarized light in the absorption band of azo-dye. The new orientation of LC was captured by the command surface because of a light-induced alignment memory effect. To describe the experimental dependencies we solved the self-consistent problem of the propagation of a circularly polarized light in the absorbing nonlinear media using the geometric optics approximation. Comparing the experimental data with numerical evaluation we obtain the basic parameters of the system: the orientation nonlinearly coefficient and the value of anchoring of the director with the polymer surface.