On the Theory of Light Propagation in Cholesteric Liquid Crystals

Abstract

The theory of the propagation of light along the axis of a cholesteric liquid crystal is considered. Two models have been used so far, viz., the spiralling dielectric ellipsoid model of Oseen, treated theoretically by de Vries, and the twisted pile of birefringent plates treated according to the dynamical theory by Chandrasekhar and Srinivasa Rao. The two models appear to give different results at long wavelengths, and the former seems inapplicable in the region of total reflection. In this paper, an exact solution of the Oseen model is found, which may be used in the entire range of wavelengths, and has a simple physical interpretation. Secondly, the model of Chandrasekhar and Srinivasa Rao is shown to agree with this solution. The approximations implicit in the work of these authors and that of de Vries are clearly brought out. A numerical example illustrating the features of the exact solution is given.