Abstract

In the past few years azo-dye containing polymeric films have been the subject of intensive investigations because of their possible application in the areas of optoelectronics, photonics and optical signal processing¹-³. The trans ⟺cis isomerization of azobenzene derivatives in bulk polymer films has been used for producing polarization hologramms^1a, optical channel waveguides^1b, writing-erazing optical memories^1c, and second order nonlinear-optical effects². Langmuir-Blodgett-Khun (LBK) multilayer assemblies of azobenzene containing polymeric materials have been used for all-optical modulation^3a, optical image recording^3b, and molecular switching^3c. However, despite this activity, the Weigert effect that is the induction of photochemical birefrengence or dichroism in certain materials, on irradiation with polarized light, has rarely been reported for organized molecular structures, or in azobenzene containing polymeric films. Here, we report on dichroism that has been induced in a monomolecular layer of azo-silane molecules self assembled on a quartz glass substrate. The Weigert effect is studied in an azo-polyglutamate polymer for spun-cast polymer films and for LBK multilayer assemblies. It will be particularly emphisized that in contrast to the LBK structures, efficient photoselection can be achieved in the spun-cast films. Finally, photoisomerization of the push-pull azo-dye Disperse Red 1 (DR1) molecule, will be shown to create an appreciable alignment of DR1 chromophores chemically attached to the side chains of a high T_g (about 210 °C) rigid main chains polyimide polymer. This may be used to help poling this kind of polymers for second order nonlinear-optical effects.

© 1995 Optical Society of America