Wave propagation in cholesteric and chiral smectic-C liquid crystals: Exact and generalized geometrical-optics-approximation solutions

Abstract

Electromagnetic wave propagations in a helical cholesteric liquid crystal and a chiral smectic-C liquid crystal are studied for the case of normal incidence. Both the exact and generalized geometrical-optics-approximation (GGOA) solutions are obtained. The two solutions are in close agreement when the period of the structure is not comparable to the wavelength of the incident wave. In particular, for a liquid crystal with small optical anisotropy, the analytic expressions for the exact solution are identical to the corresponding GGOA solutions when the pitch of the helical structure is either much smaller or much larger than the wavelength of the incident wave. With the use of the exact solution, the polarization and total internal reflection as well as the optical rotation power and circular dichroism are discussed. The results on optical rotation power in a cholesteric liquid crystal for an incident wave far from the reflection band agreed with the results obtained by de Vires and by Mauguin [S. Chardrasekner, Liquid Crystals (Cambridge University, Cambridge, England, 1977)] under the respective applicable conditions. © 1988 The American Physical Society.