Direct evidence of the failure of electric-dipole approximation in second-harmonic generation from a chiral polymer film

Abstract

Second-harmonic generation from Langmuir-Blodgett films of a polythiophene is strongly influenced by the chirality of the polymer. The polarization dependence of the process cannot be explained in the elec.-dipole approxn. Evidence of contributions beyond elec. dipoles is obtained directly from individual second-harmonic signal