SWITCHABLE DIFFRACTIVE CHOLESTERIC GRATINGS

Electrically switchable diffractive gratings based on cholesteric liqu id crystals are suggested. An electric field switches the cholesteric cell between three states: two with a uniform in-plane director and on e with a periodic in-plane director modulation. The modulated state pr oduces a Raman-Nath diffractive effect. Characteristic time of switchi ng is of the order of 10 ms. Diffractive properties depend on the pola rization of the incident beam and the direction of surface orientation . (C) 1997 American Institute of Physics.