Chapter 22 - Photobleached Gratings in Electro-Optic Waveguide Polymers

Abstract

This chapter reviews some of the efforts of the Guided Wave Optics Laboratory (GWOL) related to the writing of holographical gratings in materials that are suited to fabrication of long lifetime electro-optic (EO) waveguide devices. The process of photobleaching involves chemical reaction within the chromophore molecules in the photosensitive system. The microscopic mechanism of the photochemical reaction is likely to consist of dissociation followed by diffusion of the dissociated chromophore out of the film. The photochemical reactions inside the dye-doped polymers are complicated and have been the subject of research for many years. The chapter discusses how photobleaching of EO polymers can be used as part of the fabrication process. EO polymers are generally EO due to the alignment of the chromophore molecules with which they have been doped. Index changes in the chromophore (dye) doped polymer can be caused by the breaking of electronic bonds in the chromophore molecules. The breaking of dye molecule bonds removes absorption bands, thereby reducing the perception of color in some dye systems. The bond breaking or bleaching of the dye molecules can be induced by illuminating the polymer with light that is resonant with an isomerization reaction in the chromophore molecule. Experimental results of photobleaching studies at GWOL are also presented.