Determination of Light-Induced Deformation Characteristics of the Director Field of Nematic Liquid Crystal by Combining the Methods of Aberrational Self-Action of Light Beam and Polarization Microscopy.

Light-induced director field deformation of a nematic liquid crystal in the field of an obliquely incident laser beam is experimentally studied with aberrational self-action and polarization microscopy. Each of the methods has features associated with the geometry of the light interaction with the director. The combination of methods significantly expands the possibilities of reconstructing the light-induced nonlinear phase shift profile and the director field deformation.

Phase Structure Recording in a Nematic Side-Chain Liquid-Crystalline Polymer.

Dye-doped nematic side-chain liquid-crystalline polymers possess extraordinary large optical nonlinearity and ability to store the induced orientational deformations in a glassy state, which makes them a very promising material for photonic applications. In this study, the phase structures were generated and recorded in the bulk of a 50-µm layer of a nematic liquid-crystalline side-chain polymer, containing polyacrylate backbone, spacer having five methylene groups, and phenyl benzoate mesogenic fragment. The polymer was doped with KD-1 azodye. The director field deformations induced by the light beam close to the TEM01 mode were studied for different geometries of light-polymer interaction. The phase modulation depth of 2π was obtained for the 18-µm spacing between intensity peaks. The experimental data were analyzed based on the elastic continuum theory of nematics. The possibility to induce and record positive and negative microlenses in the polymer bulk was shown experimentally.

Optical orientation of nematic liquid crystal droplets via photoisomerization of an azodendrimer dopant.

Two sequential transformations of the orientational structure in nematic liquid crystal droplets containing a dendrimer additive (nanosized macromolecules with light-absorbing azobenzene terminal moieties) under light irradiation in the UV-blue spectral range were investigated. The origin of these transitions is in the change of the boundary conditions due to photoisomerization of the dendrimer adsorbed onto the liquid crystal-glycerol interface. It was shown that the photoisomerization processes of dendrimer molecules in a liquid crystal are accompanied by a spatial rearrangement of their azobenzene moieties, which is the key point in the explanation of the observed effects.

Communication: Orientational structure manipulation in nematic liquid crystal droplets induced by light excitation of azodendrimer dopant.

Reversible orientational transitions in the droplets of a nematic liquid crystal (NLC) caused by the change of boundary conditions under the low intensity diode illumination are investigated. Photosensitivity of NLC is achieved by the addition of the dendrimer compound with azobenzene terminal groups. Two types of NLC droplets in glycerol are considered: the spherical droplets in the bulk of glycerol and the droplets laid-down onto the solid substrate. In the second case, the first order phase transition is revealed. The effects described can be useful for the development of highly sensitive chemical detectors and microsized photo-tunable optical devices.