We report here measurements of the orientational and frequency dependence of the anomalously large second-order nonlinear optical (NLO) susceptibilities observed in guest−host DANS [4-(N,N-dimethylamino)-4‘-nitrostilbene]/PMMA [poly(methyl methacrylate)] films poled in an “in-plane” electrode configuration. The resonant response is sharply peaked (fwhm decreases by a factor of 4) in comparison to identical samples poled by standard corona field techniques. Additionally, these anomalous susceptibilities, which are oriented normal to the electric poling field, exhibit unusually strong features at long wavelengths where the linear absorption is low. We also report the first direct experimental EPR evidence for nitrogen-centered cation radicals, hence the creation of charged chromophores trapped in the polymeric matrix by charge injection from the poling electrodes. These observations are in qualitative agreement with the very large NLO response magnitudes and distinct spectral features predicted by sum-over-states perturbative calculations performed for positively charged centrosymmetric chromophore dimers and provide strong computational evidence that the observed anomalous NLO response is due to charged chromophore aggregates.

This contribution presents a quantum chemical investigation of the nonlinear optical response of charged centrosymmetric aggregates of the archetypical chromophore p-nitroaniline using an ab initio supermolecular approach. Localized hole states, responsible for aggregate nonlinearity, are predicted to be more stable than delocalized states. The calculated aggregate hyperpolarizabilities are consistently larger than in the isolated chromophore, and the mechanism giving rise to the nonlinearity is essentially “intramolecular” in nature. The aggregate formation is predicted to stabilize the positive charge and to enhance the nonlinearity. Moreover, the calculations reveal that a (formally) centrosymmetric charged aggregate can possess a substantial dipole moment the principal axis of which is oriented perpendicular to the principal hyperpolarizability tensor; the dipole moment arises because electron localization breaks the charge distribution symmetry. These results explain a number curious features of chromophoric polymer films which are electric field poled with an “in-plane” electrode geometry.

Self-assembled chromophoric multilayers having large second-order optical nonlinearities can be combined with linear guiding materials such as polymethylmethacrylate to produce two-component frequency doublingwaveguides. This approach introduces considerable flexibility in optimizing the trade-off between the overlap of waveguide mode profiles and linear absorption. Extremely low waveguide propagation losses can be achieved because electric field poling and the accompanying poling-induced optical scattering are obviated.

Various methods have been used to synthesize Ba(THD)₂ and its molecular structure has been studied using nuclear magnetic resonance. Compared with Raman and infrared spectroscopy it was found that NMR is very useful to determine quantitatively the decomposition through aging of Ba(THD)₂. The transport kinetics of Ba(THD)₂ has been studied under experimental conditions of a OMCVD reactor. It has been found that the freshly prepared Ba(THD)₂ by the reaction of Ba metal with THD ligand in anhydrous conditions with subsequent crystallization from methanol transported quantitatively without decomposition. A simple model shows that the transport kinetics corresponds to a diffusion controlled process.

Assembling quinolinium-based chromophores on silicon surfaces provides a new route to electronic control over such semiconducting surfaces. The two-step process by which the molecules are grafted on to the surface involves first coupling the organic functionality to silicon, followed by chromophore anchoring. These synthetic steps are monitored by XPS, UV-Vis and FTIR spectroscopies. Using contact potential difference measurements we found that the electron affinity of the modified silicon is a function of the molecule's dipole moment. The same technique shows a pronounced effect of the sub-nanometer siloxane-based, coupling-agent, layer by itself on the band bending and band-bending modification as function of chromophore adsorption.

In the present work we describe the design, syntheses, and use of a new barium metalloorganic precursor for barium titanate thin film deposition. Barium-containing thin films deposited by different deposition methods are widely used for various applications in optics and electronics. An important goal for applications is concerned with the production of stable, fluorine free barium-metalloorganic precursor materials, to obtain better performance photonic devices. We describe an alternative barium-metalloorganic precursor based on a calixarene ligand, its application to dip coating and thin film growth of the BaO−TiO2 family of compounds, and studies of these films by second harmonic generation. The BaTiO3 films showed promising nonlinear optical response for guided wave-applications.

We report measurements of the frequency dependence of anomalous second-order electric susceptibilities of polymer films containing hyperpolarizable chromophore guest molecules and poled using coplanar electrodes. The frequency dependence, polarization dependence, and magnitude of the observed second-order susceptibilities are radically different from those of conventional corona-field poling experiments and cannot be explained by isolated chromophore models. These observations and the results of sum-over-states perturbative electronic structure calculations argue for the importance of positively charged chromophore aggregates.