Nonlinear Optical Susceptibilities of Poled Guest−Host Systems: A Computational Approach

Abstract

Linear and nonlinear optical susceptibilities of poled guest−host polymer systems are calculated, using structures simulated by molecular dynamics. Three systems are investigated, each consisting of a poly(methyl methacrylate) (PMMA) matrix and doped with either of the one-dimensional nonlinear optical (NLO) chromophores N,N-dimethyl-p-nitroaniline (DPNA) and 4-(dimethylamino)-4‘-nitrosilbene (DMANS) or the two-dimensional NLO chromophore N,N‘-di-n-propyl-1,5-diamino-2,4-dinitrobenzene (DPDADNB). The electrical properties of the NLO chromophores are computed at the ab initio level, including correlation at the second-order Moller−Plesset (MP2) theory and frequency dispersion at the restricted Hartree−Fock (RHF) level, and with density functional theory (DFT). The permanent local fields in the bulk are small; however, their effects on the first hyperpolarizabilities are comparably large. Refractive indices and second-order susceptibilities corresponding to second harmonic generation (SHG) are calculated us...