Spectral Variations in Selective Reflection in Cholesteric Liquid Crystals Containing Opposite-Handed Chiral Dopants

The optical properties of cholesteric liquid crystal (CLC) containing a nematic host dispersed with a binary chiral dopant were investigated. The binary dopant was composed of a right-hand twist (RT) chiral agent and a left-hand twist (LT) chiral agent whose helical twisting power was much smaller than that of the RT one. With a fixed content of the RT additive, we found that the sample redshifts in central wavelength of the selective reflection as the concentration of the LT agent increases, presumably due to the increasing helical pitch caused by the racemic effect. Some other interesting results including the dopant-content and temperature dependence of the optical properties are addressed.