Surface relief gratings and complex structures photo-induced in azo-dye doped elastomer

We present the observation of surface relief gratings and complex structures recorded on azo dye doped elastomer thin film after irradiation with several spatial light configurations. More than one periodic structures are inscribed during holographic recording using different polarization state of interfering beams: intensity light patterns with different polarization states and polarization patterns. Diffraction efficiency and formationà,'s dynamic of the recorded gratings has been checked. Measurements with Atomic Force Microscope (AFM) evidence the presence of complex structures only for some pattern configurations: profiles modulation in both directions, perpendicular and parallel to the grating wave vector, are observed. Profiles and periodicity of the structures are investigated. Analyses of film surfaces after irradiation with one uniform polarized light beam make evidence of an ordered stripes structure. Only in the case of linearly polarized light beam, stripes oriented perpendicularly to the polarization direction are observed. This last observation suggests that the formation of complex structures, during the holographic recording, could be attributed to the combination of an effect of spontaneous patterning resulting from light induced surface instability, and the usual massive material displacement effect observed during the SRG formation in polymer-dye systems.