Temperature dependence of the third-order nonlinear optical susceptibilities in polysilanes and polygermanes

Optical third-harmonic generation was used to measure third-order nonlinear susceptibilities χ(3) for thin films of planar zigzag polysilanes and polygermanes. A χ(3) of 11.3×10−12 esu was measured, the largest value ever reported for a polymer with transparency throughout the visible. The value of χ(3) was found to vary substantially with thermally induced reversible changes in polymer backbone conformation and also with film thickness.