Guest-Host Crosslinked Polyimides for Integrated Optics

Abstract

We report on our approach to the development of device-quality electro-optic materials. We have sought to optimize the optical losses and processing properties first, and later to functionalize the materials having learned how to synthesize and process them for devices. [1,2] We started with perfluorinated, preimidized fully aromatic polyimides. Preimidization makes processing doped polymer systems more flexible, by making functionalizing easier (no harsh imidization process) while allowing spin coating of soluble fully-imidized polymers. Fluorination increases solubility while decreasing optical loss and refractive index. Fully aromatic polymers allow for the best high temperature properties. We found that by introducing alkylated crosslinking groups which can be photo- or thermally activated, optical losses were further reduced, so that high quality waveguides could be fabricated. [1] Another advantage of the crosslinking groups is that they open up new processing capabilities. [2] For example, cross-linking allows for simple multilayer formation, permits a liquid etch process to define waveguides, and provides a chemical hook to which chromophores may be covalently attached. We have uncovered a number of issues relating to functionalization, such as increased optical loss due to long absorption tails in the chromophore and enhanced mobility of small chromophores. We have also studied poling issues related to multilayer films. We believe that this approach, focused on the processing and operation of devices, has led to a flexible material system which shows exceptional promise for the development of electro-optic polymer devices.