Designing electro-optical polymer films: optical loss vs EO activity vs stability

Electro-optic (EO) polymer films for use in optical modulators and switches continue to show promise for lowering costs, increasing bandwidth, and allowing high levels of monolithic integration. Now more emphasis must be placed on designing EO polymer films with low optical loss while maintaining adequate EO coefficient and thermal stability. Recently demonstrated, highly rigid and polarizable polymers have quite high thermal stability, but their optical clarity has suffered. The higher optical loss in films of these highly rigid polymers is an unsolved problem at this point. Furthermore, electric-field-poled films of these rigid polymers often have lower EO coefficients, which may be due to higher electrical conductivity at poling temperature that prevents the build- up of an adequate electric field across the film. Crosslinking of moderately rigid, fluorine-containing films may provide the best compromise of thermal stability, optical clarity and EO coefficient.