Light driven motion of the nematic director in azo-dye doped liquid crystals

We show that under laser and white light action, reorientation of the nematic director for azo-dye doped liquid crystals follows a three-dimensional trajectory, composed by in and out-of-plane motion with respect to the incidence plane of the light. We relate the two components to the surface and bulk effects, respectively, and we show that the bulk contribution is mainly dominated by the photoisomerization of the azo-dye molecules.