High density bis-azo copolymers: influence of dipole-dipole interaction on electrical poling processes and realization of a Fabry-Perot modulator

摘要

The chromophore orientation distribution in photoaddressable bis-azo copolymer thin films is investigated as a function of the poling temperature and the chromophore concentration. The first, second, and third order parameters are deduced from the linear electro-optic coefficients and the linear dichroism by free-beam interferometry and angle-resolved spectroscopy, respectively. Absorption spectra obtained by density-functional calculations are compared with the experimentally observed ones and support the picture of differently aligned bis-azo dye molecules in a trans,trans-configuration. The various kinds of ordering in samples poled at different temperatures is confirmed by complementary wide-angle X-ray scattering. Furthermore, we show that a higher thermal stability for applications can be reached by fractionating the polymer, and how such a material can be successfully employed to build a large-area Fabry-Perot-Modulator using the electro-optic effect.