High-performance photorefractive organic glasses: understanding mechanisms and limitations

Since the first observation of the photorefractive (PR) effect in polymers, extensive efforts have been directed toward understanding the physics of the PR process in these systems, as well as optimizing polymer composites and glasses for various applications. Despite remarkable progress both in elucidating the mechanisms and processes contributing to the PR effect and in designing organic materials with high gain and diffraction efficiency, simultaneously attaining high refractive index modulation, fast dynamics, and good thermal properties in one material remains a challenge. Monolithic glasses represent an attractive class of PR organic materials since they possess large nonlinearities and minimal inert volume, which enhances the performance without stability problems. In this paper, we present a complete study of monolithic glasses based on a promising new class of chromophores (containing 2-dicyanomethylen-3-cyano-5,5dimethyl-2,5-dihydrofuran, abbreviated as DCDHF-derivatives). We describe thermal, photoconductive, orientational, and photorefractive properties of these materials in both red and near infrared wavelength regions. By studying the temperature dependence of various parameters, we analyze the factors that affect photorefractivity in DCDHF-based materials.