Enhanced nonlinear birefringence in hybrid aligned nematics

Abstract

We show that birefringence can be optically induced in hybrid aligned nematic (HAN) liquid crystals at normal incidence for light fields much lower than the Fredericksz threshold. In this case no threshold exists and the nonlinear optical effect at normal incidence is of the same order as that obtained with homeotropic (HOM) cells for the maximum useful angle. An analysis of the effect of the anchoring energy Ws is worked out showing that weak anchoring on the walls enhances the nonlinear effect by one order of magnitude or more.