Diffraction Gratings in Hybrid Sol‐Gel Films: On the Understanding of the Relief Generation Process

Abstract

AbstractHybrid organic‐inorganic materials based on the sol‐gel synthesis of an organically modified silicon alkoxide have demonstrated their great potential for optical applications. They offer a high versatility in terms of chemical, physical properties and macroscopic shape molding of the final component. Recently, a photolithographic process allowed the generation of relief optical elements without requiring a wet treatment to reveal the latent image. It enabled a low cost, simple and quick method for the fabrication of integrated optical components. The aim of the present paper is to give new insights into the mechanisms of surface self‐corrugation leading to gratings generation in hybrid sol‐gel films. A study of the relief formation was led by giving particular attention to the kinetic aspects of the polymerization of the organic component. The control of the CC double bonds conversion of methacrylate functionalized alkoxides in case of photopolymerization is therefore an essential issue to tailor material properties. The study also focuses on the influence of physico‐chemical parameters that govern the relief generation and underlines the particular role of temperature. Kinetics of surface corrugation point out the importance of strain relaxation, mass‐transfer by flowing and organic network formation during the photolithographic process. Some illustrations of the generated diffraction gratings are given. Interferogram of the diffraction grating obtained after 120 s exposure through a chromium mask.magnified imageInterferogram of the diffraction grating obtained after 120 s exposure through a chromium mask.