Optical Third-Harmonic Generation in Poly(p-Phenylene Benzobisthiazole) Langmuir-Blodgett Film

Abstract

Abstract The nonlinear optical anisotropy of ply(p-phenylene benzo-bisthiazole) (PBT) Langmuir-Blodgett (LB) films has been investigated by optical third-harmonic generation measurement. Polymer backbones of PBT in LB films were aligned along the dipping direction. The χ(3) xxxx, χ(3) yyyy and χ(3) xxyy values were determined by rotational Maker fringe method to be 11.3 × 10−12 esu., 1.5 × 10−12 esu. and 0.9 × 10−12 esu, respectively. These nonlinear optical anisotropies can be explained well by assuming a Gaussian orientational distribution of one-dimensional π-conjugated chains.