No abstract

It was shown that irradiation of a nematic liquid crystal doped with metal nanoparticles in the visible near the plasmon resonance band led to strong thermal changes of the refractive indices. The effect was studied by recording of dynamic optical gratings in the colloid. Nanoparticles "worked" as effective nano-heaters in a matrix causing the order parameter decrease around the particles. A large nonlinearity parameter (n (2) ≈ 10(-2) cm(2)/kW and fast response (≈ 0.7 ms), with no detectable particles' aggregation and excellent photo- thermo-stability make these colloids potentially attractive nonlinear optical media. Application of a dynamic holography technique allowed measuring the coefficients of thermal conductivity of the liquid crystal along the director k (||) = (0.4 ± 0.02) W m(-1)K(-1) and perpendicular to the director k (⊥) = (0.2 ± 0.01) W m(-1)K(-1).

Defect lines arrays are created in liquid crystal exploiting periodic arrangements of twisted domains with opposite handedness. The defect lines self-organize in a planar cell guided by a polarization hologram recorded in one aligning substrate that provides planar periodic alignment. Depending on the relationship between the cell thickness d and the hologram pitch Λ, the array period can be either Λ or 2Λ. An external voltage enables to switch the spatial periodicity of the defect lines from 2Λ to Λ and also to control their shape and location. A modeling of the observed twisted arrangements is reported.