Light induced anchoring and memory effects in dye-doped liquid crystals

We present a new type of effective photoregulation of the LC orientation on an aligning surface through light action upon the liquid crystal bulk. The illumination of an azo-containing LC bulk with polarized light is found to induce both stable (in time and temperature) high-resolution alignment onto the rigid surface and dynamic sliding of the director over the surface. Typical times of the director sliding over the aligning surface are of the order of 1 ms. Both effects are characterized by extremely small light intensities (as low as 10-1 J/cm2) and seem to be very promising for the development of optical devices for information processing and high density information storage. Light-induced surface memory effects are also observed in these systems as a consequence of induced anchoring of the molecular director. This technique has been applied to record both stationary and dynamic holograms with a spatial resolution of 7 μm. The surface memory effects have been applied to record both binary and gray scale images. As compared to other methods used in these materials the highest sensitivity and spatial resolution can be achieved: energy densities as low as 10-1 J/cm2 were sufficient to write gratings with a resolution better than 100 lines/mm.