NONLINEAR-OPTICAL SUSCEPTIBILITY OF CONJUGATED POLYMERS - DC KERR-EFFECT

With the help of Keldysh diagram technique we rigorously calculate the nonlinear optical (NLO) susceptibility of a conjugated polymer in one electron two band continuum Linearized model with constant dimerizati on for the d.c. Kerr effect (Electroabsorption, EA). The explicit anal ytical formula obtained for chi(EA)((3))(omega) is accurate in the ent ire frequency range in the lowest order in the quasiparticle relaxatio n constant. Its comparison to the results on the quadratic electro-opt ic nonlinear susceptibility in PTV reveals qualitative agreement betwe en theory and experiment.