Photorefractive properties of a polyimide containing thiacarbocyanine dye J-aggregates

The photorefractive properties of a polyimide containing J-aggregates of a thiacarbocyanine dye were examined. Measurements were made with a holographic apparatus at Ar-Kr laser wavelengths of 647 and 514 nm. The J-aggregate and the monomeric form of the dye, respectively, are responsible for the photoelectric sensitivity at these wavelengths. It was shown that the J-aggregates are also responsible for the nonlinear optical properties of the polymeric system. The combination of these features determines the photorefractive characteristics of the polymer composite: under interference conditions, the intensity of one of the interacting beams (signal beam) increases at the expense of extinction of the other (pumping) beam. The difference between the beam-coupling gain coefficient Gamma and the absorption coefficient alpha increases at 647 nm from 217 to 361 cm(-1) with the increasing strength of a constant electric field E-0 applied to the layer from 16 to 123 V/mum. Only the samples containing J-aggregates display the photorefractive effect at 514 nm.