Abstract
In this work we use the Q-tensor order parameter to express the elastic free energy of a nematic liquid crystal. This correctly preserves the +n/−n symmetry and thus allows the modelling of defects. Using this, we calculate director profiles for cells containing surface relief gratings. Director profiles are presented which demonstrate that the cell supports two stable director configurations, in agreement with previous investigations [1-3]. The director profiles calculated are used in conjunction with Finite-Difference Time-Domain optical modelling to simulate the diffraction from the two stable states. The results of these simulations are then compared with experimental results for a cell fabricated with a relief grating on one internal surface. Diffraction strength is measured as a function of incident angle and as a function of incident polarisation.