Continuous electro-optic effect in twisted structures of achiral smectic C liquid crystals

Existence of a continuous electro-optic (EO) effect is predicted in twisted structures of achiral smectic C liquid crystals (Sm C LCs). In a twist geometry, the smectic layers are formed perpendicular to the substrates such that the director is twisted by twice the molecular tilt on going from one surface to the other. In this configuration, the molecules are forced to continuously rotate along the cone surface formed by the requirement that the molecules be tilted with respect to the layer normal and pinned at the surfaces. The basic principles of the optical modulation in such devices are similar to those in twisted nematic LC structures except for the existence of smectic layers and the intrinsic biaxiality.