Nonlinear optical materials characterization studies employing photostability, hyper-Rayleigh scattering, and electric field induced second harmonic generation techniques

Several electro-optic (EO) chromophores were characterized using a photobleaching test setup, hyper-Rayleigh scattering (HRS), and electric field induced second harmonic generation (EFISH). Photostability figure-of-merits, B/sigma, were determined for EO materials at 1.55 mum. A newly developed model that better describes chromophore photodecomposition was used to determine the B/sigma of several chromophores; many of these chromophores were found to have more than one photodegradation pathway and thus, more than one photostability B/sigma value. The rate of EO material photodecomposition was affected by the addition of singlet oxygen quenching materials. Photobleaching tests conducted in an inert atmosphere greatly enhanced EO material photostability. These results, along with those of the singlet oxygen quencher addition, suggest that photooxidation is the primary pathway for chromophore decomposition. Systematic studies of a number of EO polymer systems were performed, where parameters such as polymer host and chromophore architecture were varied. Estimations of device lifetimes based on photostability figure-of-merits were calculated. HRS and EFISH were employed to measure the first-order molecular hyperpolarizability, beta, of several EO chromophores. Theoretically calculated beta-values were compared to experimentally measured beta-values in order to verify computational results and define structure-function relationships of chromophores with varying chemical architectures. Hyperpolarizabilities of four common EO chromophores were measured using HRS and EFISH; both techniques were found to give rise to similar beta-values. The dependence of beta and mubeta on dielectric environment (epsilon) was investigated for YLD156 and CLD-1 in various solvents and compared to theory.