Cholesteric Liquid Crystal Transmission Profile Asymmetry

The selective reflection profile of a cholesteric liquid crystal is asymmetric when (a) for light incident parallel to the cholesteric helix axis, the incident polarization vector, E, is at an angle other than 45 degrees to the molecular director at the first surface or (b) for light incident oblique to the cholesteric helix axis, the incident polarization is S- or P-polarized. We confirm these effects using cyclic polysiloxanes. Further, we show that the use of a new form of cholesteric liquid crystal called flakes allows the first experimental separation of the asymmetry due to the surface and that due to the bulk.