Hydrodynamic effects in the optically induced reorientation of nematic liquid crystals

We present a model to describe the first stages of the reorientation process of a nematic liquid crystal under the action of an obliquely incident optical field. The presence of hydrodynamic backflows associated with the reorientation in both, a homeotropic and a planar geometry, is explicitly taken into account. The phase change and the inverse focal length are calculated analytically and evaluated for the nematic phase of CBOOA. It is shown that for a homeotropic arrangement, hydrodynamic backflows may produced a significant and, in principle, measurable change as high as 75% in these properties.