STUDIES OF RESONANT AND PRERESONANT FEMTOSECOND DEGENERATE 4-WAVE-MIXING IN UNORIENTED CONDUCTING POLYMERS

Degenerate four-wave mixing with femtosecond time resolution is used to measure the magnitude and transient response of the third-order nonlinear optical susceptibility chi-(3) (omega;omega, - omega,omega) at 620 nm in nonoriented conducting polymers including polydiacetylene, polyacetylene, polyaniline, polydiethynylsilane, polythiophene, and polythiophene derivatives. Resonant and nonresonant excitations influence the magnitude and transient response of chi-(3). The electronic response is instantaneous for preresonant excitation, but for resonant excitation it has ultrafast and slow components which illustrate photoexcitation dynamics. The magnitude of chi-(3) for all of the polymers is in the range from 10(-10) to x 10(-8) esu depending on the energy difference between the laser excitation and the polymer absorption maximum.