Photoinduced surface deformations on azobenzene polymer films

Laser-induced surface deformation and surface relief grating formation at d ifferent intensity levels on azobenzene-functionalized polymer films were i nvestigated. The surface deformation profile induced by a Gaussian laser be am at low intensities reveals strong polarization dependence and establishe s that an optical-field component in the direction of the optical-field gra dient is essential for this deformation process. A theoretical analysis bas ed on the optical-field gradient force model is presented to account for th e deformation behavior at low intensities. In the higher-intensity regime, however, a different mechanism is found to dominate the surface deformation process. Simultaneous formation of two different types of topographic grat ings is observed in a two-beam interference experiment. The phase relations hip between these surface relief gratings and the interference intensity pa ttern was deduced based on the results from the single-beam experiments. Th e erasing behaviors of the two distinct surface relief gratings were experi mentally investigated to highlight the two mechanisms involved in these gra ting recordings. (C) 1999 American Institute of Physics. [S0021-8979(99)039 20-1].