Modelling reversible optical data storage in photoanisotropic polymers

Among the potential materials for reversible optical data storage the liquid crystalline azobenzene side-chain polymers are especially promising due to their unique optical properties. Holograms of very high diffraction efficiency can be written (and erased) by laser illumination in this material and, equally important, the holograms are exceptionally stable. In order to clarify the mechanism responsible for these remarkable properties we have constructed a mean-field theory [1] of the storage process. It has been shown that the inter-molecular forces are essential for an understanding of the way in which holograms are gradually stored during illumination. An example of the comparison between theory and experiment is shown in Fig. 1. In addition, the mean-field theory has provided an explanation for the stability of the holograms. This explanation is based on theoretical results showing that the optical data are stored in entire domains rather than in individual molecules. Hence, the superior stability of a large domain in comparison to a single molecule is transferred to the optical hologram.