Optimization of the efficiencies of photorefractive polymers: Correlations between viscoelastic properties and electro-optical responses

The photorefractive properties of low glass transition temperature (T_g) doped polymers are essentially ruled by the ability of the push-pull chromophores to align along the electric field. Therefore, a high rotational mobility is therefore needed for these non linear optical chromophores incorporated in the matrix. However, even if the influence of T_g on the photorefractive performances of guest-host polymers has been previously pointed out, this unique parameter is not sufficient to take into account the viscoelastic properties of the matrices. A complete study of the orientational dynamics of chromophores in various low T_g doped polymers, investigated by dielectric spectroscopy, second harmonic generation and electrooptical dynamical measurements, is presented. The results are fully interpreted and modeled by rheological laws used to describe the viscoelastic behavior of polymers. Finally, the influence of the average molecular weight is also analyzed and then demonstrates the interest of using low molecular weight polymers.