Material optimization for electro-optic modulation and cascading

A large effort has been devoted to the preparation of organic polymeric materials for electro-optic modulation and more recently for cascading based processes. These materials contain push-pull chromophores either incorporated as guest in a high T_g polymeric matrix (doped polymers) or grafted onto the polymeric matrix. These systems present several advantages but require significant improvement at the molecular level - by designing optimized chromophores with very large molecular figure of merit specific to each application targeted. The sol-gel route was used to prepare hybrid organic-inorganic materials, for the fabrication of amorphous solids of various shapes (bulk, thin films…). The results obtained on optimized chromophore-doped poled thin films emphasize that intermolecular interactions have to be taken into account, as already pointed out by Dalton and coworkers. By combining a molecular engineering strategy for getting large molecular figure of merit and by controlling the intermolecular dipole-dipole interactions via both tuning the push-pull chromophore concentration and the incorporation of screening carbazole moieties in high concentration. This strategy allows us to obtain a r₃₃ coefficient of about 15 pm/V at 633 nm with the classical DR1 azo-chromophore and a r₃₃ of about 50 pm/V at 831 nm for a new optimized chromophore structure. In parallel, these thin films are being processed to be used as passive components for integrated optics.