Approaches to polymeric nonlinear optical materials. Theoretical and synthetic design strategies

Two aspects of the rational construction of polymeric frequency doubling materials are described. First, a computationally effecient SCF-LCAO MECI π-electron theoretical approach has been developed to aid in chromophore design and to better understand molecular electronic structure/architectural features which give rise to high quadratic molecular optical nonlinearities (β). Selected high-β chromophores are then covalently linked via several synthetic procedures to robust, glassy, film-forming chloromethylated or hydroxylated polystyrenes. By this procedure, it is possible to achieve very high chromophore densities in polymeric films with good optical transparency and chemical stability characteristics. Coating of these polymers onto conductive glass, followed by electric field poling near T_g yields robust films with high persistent SHG efficiencies. As an example, films of poly(p-hydroxystyrene) functionalized with N-(4-nitrophenyl)-L-prolinol exhibit d₃₃ as high as 18 × 10^-9 esu at 1.06 μm (16 times the corresponding value for KDP).