Determination of the direction of the "easy" axis at a twisted nematic liquid crystal-wall using half-leaky guided modes

Theoretical analysis and numerical modeling indicate that, under high field s, the director of a thin region of liquid crystal close to the wall of a t wisted nematic cell returns to the "easy" axis on the interface. Polarizati on conversion reflectivity signals are recorded for half-leaky guided modes from a twisted nematic cell subject to high ac fields. By fitting model th eory to reflectivities recorded for a particular region of incidence angles , the director twist at the cell walls is deduced. In the high-field limit, this then gives the original director alignment axis, the easy axis, at th e wall of a twisted nematic cell. (C) 2000 American Institute of Physics. [ S0021-8979(00)02921-2].