Electric-field controlled color effect in cholesteric liquid crystals and polymer-dispersed cholesteric liquid crystals

In cholesteric liquid crystals with positive dielectric anisotropy an electric-field induced texture with unusual properties was observed. This texture appears after the reduction of the electric field during the transition from the homeotropic nematic state into the planar cholesteric one. The angular and the electric-field dependence of the spectral characteristics indicate that this state possesses diffractive grating properties. A voltage controlled color shift and a laser beam deflection are possible. An electric-field controlled cholesteric diffractive grating texture was also observed in polymer-dispersed films. In this case the electric-field induced transition into the homeotropic state is not necessary. (C) 1996 American Institute of Physics.