MAGNETIC-FIELD CONTROLLED OPTICAL-PHASE RETARDATION IN A HYBRID NEMATIC CELL

We have studied the phase retardation of linearly polarized light in a hybrid nematic liquid crystal cell. For a certain range of directions of the applied magnetic held the phase retardation is found to change non-monotonically with the magnetic induction. The observed behaviour is described rather well by the standard Frank elastic theory. The co rrections resulting from subsurface deformations, which are characteri stic both for second order elasticity approach and for surface held th eory, are also considered. The analysis of the experimental data sugge sts that the presence of distortions in the zero-field director config uration is the necessary condition for the non-monotonic phase retarda tion, which implies that such an experiment could be used for the dete ction of misalignment of the effective pretilts in a nematic cell.