Electro-optics in thermopoled polymer films

Measurements of the electrooptic (EO) properties of polar polymetric films are presented. The polar order is induced by thermopoling using fixed contacts. In doped films, high doping concentrations (20% wt.) have been achieved of the nonlinear organic molecule 2-(N,N-dimethylamino)-5-nitroacetanilide, DAN. The EO coefficients obtained include a contribution from the host polymer in the case of a polycarbonate host where films have EO coefficients higher than those of comparably doped PMMA materials. Among `side-chain´ polymers the authors found that poly(4-vinylpyridine), P-4VP, obtained commercially, also can be poled efficiently and yields moderate EO coefficients. An experimental value for the microscopic nonlinear figure of merit μβ in P-4VP is calculated and compared with a theoretical value. The resulting mismatch reveals that the simplified thermodynamic model may be inappropriate for this side chain polymer and that low-frequency contributions to the nonlinearity may be significant