High-speed analog refractive-index modulator that uses a chiral smectic liquid crystal.

We demonstrate a fast liquid-crystal analog phase modulator composed of a homeotropically aligned electroclinic chiral smectic liquid crystal. Pure phase modulation is obtained by electrical modulation of the refractive index of the liquid crystal. A refractive-index change of 0.045 can be obtained at a 5-micros switching speed with a 15-V/microm applied electric field by use of the commercial electroclinic chiral smectic liquid crystal mixture BDH764E. This results in a pi phase modulation depth at lambda = 0.633 microm in a device of 10-microm thickness.