Optically induced reorientation in a hybrid aligned nematic liquid crystal cell

Optically induced molecular reorientation in nematic liquid crystals is an interesting phenomenon, suitable of many practical applications, due to the large electric and optical anisotropy of such materials in the nematic phase. Therefore great importance has the study of the dynamics of the molecular reorientation. In the usual configuration the cell contains a homeotropically aligned nematic liquid crystal and a linearly polarized laser beam impinges on it. However, the presence of a Freedericksz transition requires the use of some experimental ingenious contrivances: such as the application of a magnetic field or performing the experiment only for a large enough incidence angle. We show here that the molecular reorientation dynamics of a nematic liquid crystal can be easily studied without any magnetic field, even at, normal incidence, using a hybrid aligned nematic liquid crystal cell: i.e. a cell with homeotropic alignment, on one boundary and planar alignment on the other