DYNAMIC HOLOGRAPHIC GRATINGS IN METHYL RED-DOPED NEMATIC LIQUID CRYSTALS

Abstract

Orientational photorefractivity in liquid crystals doped with azo dye MR crystals is studied. The experiments are carried out with no voltage applied. Dynamic behavior and its dependence on writing beams intensity are presented. When excited by light, the dye tends to bond to the cell surface. Such an effect is irreversible and leads to the permanent component formation in diffracted signal. This is not beneficial for applications where change of written information is required (OASLMs, dynamic holography, all-optical switching). The process was strongly suppressed and was virtually eliminated for the light intensities used, by the choice of materials for alignment surfaces.