Electric field control of permanent gratings in dye-doped liquid crystals

Summary form only. In recent years the discovery and subsequent research into photorefractive-like gratings in liquid crystals (LCs) has opened new possibilities. We investigated liquid crystal samples (5CB) doped with a relatively high concentration (above 1%) of a Methyl Red dye. At 488 nm, the transmission through our samples was only 58%. We observed that permanent gratings can be created in such samples without any polymer coating of the surfaces, provided that the product of the illumination time and the incident intensity was above a threshold. These permanent gratings, both one and two-dimensional persisted in time and some residual diffraction could also be detected above the liquid crystal phase transition.