Groove depth dependence of the anchoring strength of a zero order grating-aligned liquid crystal

Abstract

The influence of in-plane electric fields on the twist profile of a liquid crystal aligned by nondiffractive (zero order) gratings has been explored using an optical guided mode technique. The liquid crystal is studied in a novel cell geometry comprising one rubbed polyimide alignment layer and one zero order diffraction grating. Comparison of the director-distorted profiles with predictions from elastic continuum theory allow both the twist elastic constant of the bulk liquid crystal and the azimuthal anchoring strengths at the two surfaces to be determined. Experiments have been performed on different depth gratings. Good agreement with the Berreman topological alignment model has been achieved for fairly shallow gratings, but not for gratings with deeper groove profiles. This implies that the theory needs modification to account for deep gratings.