Light interaction with nematic liquid crystals doped with azocompounds of different molecular weight

The presence of light-absorbing dopants in nematic liquid crystals (NLCs) can induce orientation nonlinearities conditioned by the torque due to changing the intermolecular forces at dopant excitation. It was shown that large nonlinearities are caused by high-molar-mass substances (comb-shaped polymers and the homodendrimers with the generation number m = 1,5) containing azobenzene chromophores. The nonlinearities induced by polymers and the dendrimer with m=5 were negative (director n rotates perpendicularly to the light field E, thus decreasing the refractive index of the e-wave) in contrast to the low molar-mass dyes similar in structure to the azobenzene chromophores and the dendrimer with m = 1, in which case the nonlinearity sign changes with the angle between E and n.