Theoretical study of second-order non-linear optical properties of pyrromethene dyes for photonic application

Second-order non-linear optical properties and the ground state dipole moment of 2, 6-, and 8-substituted dipyrromethene-BF2 complexes were evaluated using ab initio quantum mechanical methods and compared with those of a standard push-pull chromophore. The theoretical values obtained are discussed in terms of the different contributions of each spatial region using the electron density derivatives with respect to an applied electric field. As results, an origin for the second hyperpolarizability and a methodology for improving the performance of these compounds are proposed. The two-level model has been use to study the electro-optic properties of the substituted dipyrromethene-BF2 complexes, and the applicability of this method has been discussed in terms of the electron density derivatives.