Photoassisted alignment and formation of polarization gratings in a ferroelectric liquid crystal Original Research Article

The photoinduced isomerization of a guest chiral thioindigo dye causes an increase in the spontaneous polarization of a ferroelectric liquid crystal (FLC) host, which is used to control the dielectric torque exerted on the FLC film by a dc electric field. The resulting reorientation of the FLC director and modification of domain walls lead to a significant change of the average birefringence of the film. This birefringence photomodulation is used to create electric-field controlled dynamic holograms. The diffraction efficiency of holograms is found to depend resonantly on the applied dc voltage. Non-monotone dynamics of reorientation is observed for step-like voltage changes under continuous light illumination. Dynamic holography, resonant photoexcitation, light scattering, polarized microscopy and polarization techniques are used to study these phenomena.