Characterizing the NLO Chromophore Orientation of Polymeric Film by Electroabsorption Spectroscopy

Abstract

The dispersion of third-order nonlinear coefficients and of three different NLO(nonlinear optical) polymer films were determined by electroabsorption spectroscopy. The first material investigated is an epoxy-based polymer BP-2A-NT, with azobenzene NLO chromophore 4-[((4-nitrophenyl)(azo)phenyl)azo)]aniline in its side chain. The other materials are two polydiacetylenes, poly(BPOD) and poly(4-BCMU), in which the( 3de)localized polymer chains contribute to the third-order nonlinearity. The complex spectrum of of each material is very similar in shape to corresponding spectrum. The ratio of to is 3.2 for BP-2ANT, 1.5 for both poly(BPOD) and poly(4-BCMU). These ratios indicate that the distribution of the side-chain NLO chromophores of BP-2A-NT is very close to three-dimensional isotropy, and the distribution of the main-chain chromophores of poly(BPOD) and poly(4-BCMU) is concentrated on the film plane.

SECOND-ORDER NONLINEAR OPTICAL SUSCEPTIBILITIES OF POLY[(HEXA-2,4-DIYNYLENE-1,6-DIOXY)DIBENZOATES] CONTAINING AZO CHROMOPHORE DISPERSE RED 19 BY ELECTROABSORPTION SPECTROSCOPY

“…7,8 There are a few studies to determine second-order NLO coefficients by EAS, but they were determined only through second-order EAS measurements detecting the components quadratically dependent on the applied electric field, i.e., third-order NLO response. [9][10][11] Theoretically speaking, second-order NLO susceptibility χ (2) can be directly determined by first-order EAS measuring a component linearly dependent on the applied electric field. In this work therefore, the second-order NLO susceptibilities of the benzoate polymers, shown in Scheme 1, were determined by the first-order EAS, and compared with values previously obtained by SHG measurements.…”