Surface-mediated light-controlled Friedericksz transition in a nematic liquid crystal cell

Surface-mediated director reorientation in a pure nematic liquid crystal (L C) cell in the presence of both a dc and low-power optical field has been o bserved. A surface-dependent lowering of the Friedericksz transition voltag e in a planar cell upon light irradiation was found. It is believed that th is effect is due to a light-induced change in the near-surface ion concentr ation in the presence of a dc field and a photosensitive surface. Enrichmen t in the ion concentration near the surface causes a redistribution of the electric field in the cell and its localization near the surface. As a cons equence, the energy of interaction between the LC and the dc field near the surface overcomes the anchoring energy and results in the director reorien tation. (C) 2001 American Institute of Physics.