Photoinduced birefringence and diffraction efficiency in azo dye doped or grafted polymers: Theory versus experiment of the temperature influence

We have investigated the influence of the temperature on the photoinduced birefringence as well as on the diffraction efficiency of azo dye doped or grafted polymers. The samples are composed of three polymer matrices containing 2, 5-dimethyl-4-(p-nitrophenylazo anisole). We propose two theoretical models to explain the experimental increase of both phenomena when the temperature is decreased, Models are based on the statistical angular distribution of the chromophores that depends on the intensity of the polarized laser beam in the media, counteracted by the thermal agitation. Parameters introduced in both models can be used to characterize the polymeric system properties.