Anisotropy of the photoinduced translation diffusion of azo-dyes

Abstract

Large-amplitude holographic surface relief gratings are optically induced by resonant visible exposure in azobenzene dye-containing polymers. We propose a simple diffusion model accounting for the essential features of surface relief grating formation. It is based on the anisotropic 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 excitation direction. The model accounts for intensity, grating-pitch and polarization dependencies. Understanding of this process appears essential for holography applications. It opens new perspectives associated with optically controlled anisotropic diffusion.