ANISOTROPY OF THE PHOTOINDUCED TRANSLATION DIFFUSION OF AZO-DYES

Large-amplitude holographic surface relief gratings are optically indu ced by resonant visible exposure in azobenzene dye-containing polymers . We propose a simple diffusion model accounting for the essential fea tures of surface relief grating formation. It is based on the anisotro pic diffusion of azobenzene-dyes in polymer matrices further to their photoinduced trans-cis isomerization cycles. The essential feature of the model is that dye-molecules undergo a 1D-random-walk along their e xcitation direction. The model accounts for intensity, grating-pitch a nd polarization dependencies. Understanding of this process appears es sential for holography applications. It opens new perspectives associa ted with optically controlled anisotropic diffusion. (C) 1998 Elsevier Science B.V.