An experimental study of the anomalous transmission (Borrmann Effect) in absorbing cholesteric liquid crystals

Abstract

It has been shown previously that in analogy with the Borrmann effect in X-ray diffraction from crystals there is an anomalous increase in the transmitted intensity near the Bragg reflection band in an absorbing cholesteric liquid crystal. In this communication detailed experimental studies of this effect carried out on thin films of mixtures of cholesteryl nonanoate and p-azoxyanisole of different concentrations are reported. Numerical calculations based on the dynamical theory of reflection are also presented. The theoretical curves of circular dichroism versus wavelength are in qualitative agreement with the experimentally observed features.