Picosecond transient grating study of nonlinear optical composites: sol-gel processed poly (P-phenylene vinylene)/silica and V₂O₅ composite films

Elastic moduli of poly (p-phenylene vinylene) (PPV) film and sol-gel processed PPV/silica and PPV/V₂O₅ composite films are determined by using the technique of a laser-induced acoustic phonon in a degenerate four-wave mixing phase conjugate geometry. The acoustic speed as a function of the orientation of the films was also measured and found isotropic in all three cases when films were prepared on a substrate and thermally treated in situ. In the case of PPV, the Young's modulus of the PPV film on the substrate is equal to 15.6 GPa, which is comparable with a draw ratio of 3, of uniaxial stretched film. Although the Young's modulus of PPV is decreased when doping inorganic glasses, the high optical quality composite films can be obtained by adding SiO₂ or V₂O₅ in the PPV. This technique is demonstrated to be another alternative to measuring the Young's moduli of materials on a substrate, which cannot be done with the convention three-point flexural method.