Abstract

Conjugated polymers and long polyenes exhibit large third order nonlinearities, both near and off resonance.^[1−3] There has been debate recently concerning the role of two photon States in the nonlinear optics of these materials. It has been suggested that the two photon state located nearest to, but above (in energy) the one photon allowed state dominates the nonlinearity.^[4] We have used third harmonic generation (THG) to study χ⁽³⁾ (3ω) in the conjugated polymers poly-4BCMU and two poly thiophenes, as well as the polyene ß-carotene to test this hypothesis.

© 1992 IQEC