An analytical expression for the optical threshold in highly twisted nematic systems with nonzero tilt angles at the boundaries

Abstract

It has been shown recently that steep optical thresholds can occur in twisted nematic configurations with tilted boundary conditions. This is the case when the twist angle φ is between π and 2π. We have derived an analytical expression for this threshold, utilizing the results from a numerical evaluation of director patterns with a computer program. The consequences of the dependence of the threshold on the relevant physical parameters are discussed and the theory is compared with experimental data. Also we point out the differences with respect to the threshold equation for the conventional 90°-twisted nematic configuration.