Electro-optic Pockels and Kerr effects for the determination of χ^(2) and χ^(3): thin films of side-chain polymers containing dimethylaminonitrostilbene and of the polydiacetylene poly-(butoxycarbonylmethyleneurethane)

Abstract

A simple reflection method that is based on ellipsometry and the electro-optic Pockels and Kerr effects is adapted for the determination of the electro-optic susceptibilities χ((2))(-ω; 0,ω) and χ((3))(-χ; 0, 0, ω). Measurements were made on materials that consist of centrosymmetric molecules like the polydiacetylene poly-(butoxycarbonylmethyleneurethane) (poly-4BCMU) and on a noncentrosymmetric poled sidechain polymer that contains dimethylaminonitrostilbene (ANS). The results are compared with those acquired by other methods (e.g., second-harmonic generation, third-harmonic generation, and degenerate four-wave mixing). Large differences occur, especially for the χ((3)) values. The effects of mechanical strains from electrostatic forces and from the field-dependent change of the absorption are discussed.