The reflection, transmission, optical activity, and extinction ratio of a series of mixtures of cholesteryl oleyl carbonate, cholesteryl nonanoate, and cholesteryl chloride of different proportions were measured. The wavelength of minimum transmission (λo), maximum rate of change of optical activity, and minimum extinction ratio were found nearly to coincide. The bandwidth of these phenomena is of the order of 500 Å. The optical rotation asymptotically approaches plus and minus infinity at λo. The variation of λo with temperature is linear between 20°C and 35°C with a slope of 50 Å°C-1. By varying the composition, λo could be varied from 5000 Å to 11000 Å.
L. Melamed and D. Rubin, "Selected Optical Properties of Mixtures of Cholesteric Liquid Crystals," Appl. Opt. 10, 1103-1107 (1971)