title: Anomalous intensity dependence of optical reorientation in azo-dye-doped nematic liquid crystals.
abstract: The intensity dependence of optical nonlinearity in a nematic liquid crystal doped with an azo-dye is investigated. The reorientational part of the nonlinearity changes from self-defocusing to self-focusing character while the intensity passes through the saturation value of trans-cis photoisomerization. This observation, in accordance with previous models, indicates that the optical torque generated by the trans-isomers is of opposite sign than the torque generated by the cis-isomers. At very low intensities a further reorientational nonlinearity was found, which is attributed to light-induced orientational redistribution of adsorbed molecules at the surface.
authors.affiliation: Politecnico di Torino, and INFM, Corso Duca degli Abruzzi 24, 10129 Torino, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Becchi
authors.forename: I
authors.initials: I
authors.lastname: Janossy
authors.forename: D S
authors.initials: DS
authors.lastname: Shankar Rao
authors.forename: D
authors.initials: D
authors.lastname: Statman