Abstract

F. Kajzar et al.,¹ have previously reported dispersion measurements of only the magnitude of the third order nonlinear susceptibility of polythiophene films. We have performed tunableTFIG measurements in the range of 1 to 2µm on poly(3-butylthiophene) and poly(3-decylthiophene) thin film polymers. Both the magnutide and the phase dispersions of χ⁽³⁾(3ω) agree with a three level model. This model indicates the presence of a two-photon state below the first dipole allowed one-photon state. The transition dipole moment between both excited states dominates the dispersion of the magnitude and the phase of χ⁽³⁾(3ω) near the three photon resonance.

© 1990 Optical Society of America