Abstract

Recently we have observed the formation of large amplitude and stable surface relief gratings directly produced on epoxy-based nonlinear optical polymer films with Disperse Orange 3 azobenzene side groups.¹ The surface relief gratings were produced upon exposure to an interference pattern of polarized laser beams at modest intensities without any subsequent processing steps. Very similar results of the formation of the surface relief gratings were also independently reported on an acrylate polymer with Disperse Red 1 azobenzene side groups by Rochon et al.² A surface modulation depth of more than 1000 Å has been observed. The intensities of the writing beams were well below the power required for ablation of the polymer. The gratings could be erased by heating the polymer above its glass transition temperature (T_g) and the writing and erasing cycles could be repeated. While it was already known that irradiation of a polarized laser beam could result in orientation of the azobenzene groups leading to birefringence in the polymer film,³-⁷ such a large surface change on the polymer film solely due to the alignment of molecules was not expected and seems to have its origins due to new optically induced processes which have not been explained so far. Large scale molecular motion and volume change due to reorientation seemed to be occurring simultaneously.

© 1995 Optical Society of America