Photorefractivity in ferroelectric liquid crystals

The first observation of photorefractivity in ferroelectric liquid crystals (flcs) is reported. The flcs are doped with the easily oxidized chromophore perylene, which also functions as the sensitizer. The electron acceptor di-butyl-pyromellitimide is added to induce photoconductivity through an efficient intermolecular electron transfer reaction to produce mobile ions. A strong dependence on the orientation of the wavevector of the optical interference pattern and polarization of the writing beams relative to the orientation of the flc molecules is observed. The results are interpreted as an orientational photorefractive effect in which the net polarization of the flc couples linearly to the space-charge field as opposed to nematic liquid crystals in which the dielectric anisotropy couples to the square of the space charge field.