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Abstract: A highly stable second-order nonlinear optical multilayer film was constructed on insulating substrates using the electric-field-induced layer-by-layer assembly technique. The substrates used in this method could be arbitrary. In another, the substrates could be modified with polyanion solution by spin coating as cladding layer. Then, the nonlinear optical multilayer films were assembled on the cladding layer directly by the electric-field-induced layer-by-layer assembly technique. The resulting cross-linked multilayer films fabricated by this method displayed high optical transparency, good thermal stability, and excellent nonlinear optical properties which can be made into waveguide devices directly. [Copyright &y& Elsevier]

In this paper, a new type of single-mode embedded dye-doped electro-optic (EO) polymeric waveguide switch based on cross-linkable negative photoresist was successfully designed and fabricated using direct photodefinition technique. The optical properties of the UV cross-linkable poled polymer were characterized. By optimizing the poling temperature and the dopant levels of Disperse Red 1, the DR1/SU-8 material showed excellent photostability and exhibited an EO coefficient, \gamma33, of 25 pm/V. The characteristic parameters of both the waveguide and the electrode were carefully designed and simulated by MATLAB program. The Mach–Zehnder interferometer switch on-off time obtained was about 6 \mus. The new fabrication technique is a simple, rapid, and controllable process. The easy-to-fabricate waveguide structure is suitable for planar active lightwave circuit applications. The dye-doped polymer photosensitive waveguide devices will be very useful in realizing EO modulators and switches. [ABSTRACT FROM AUTHOR]

Abstract: This work focused on the development of a novel method for molecular level assembly and processing of inorganic–organic hybrid second-order nonlinear optical (SONLO) multilayer films. Aromatic diazo group linked silicon sol was first synthesized and used as a polycation. This oligomer was assembled into inorganic–organic hybrid SONLO multilayer films by electric-field-induced layer-by-layer assembly technique with a low molecular weight chromophore molecule as an anion. After UV irradiation, the electrostatic interaction between layers converted to covalent bonds. Large second-harmonic generation signal of the assembled film was observed, which confirmed that the chromophore in the film had a high degree of molecular orientation as assembled under the electric field. As the cross-linked structure and silicon oxygen meshwork in the films, the resulting inorganic–organic hybrid multilayer films displayed good thermal and chemical stability, and excellent NLO properties. [Copyright &y& Elsevier]

A novel method for the preparation of thin films of Ag nanoparticles is reported. Using mercaptoacetic acid as the stabilizing agent, AgI nanoparticles were prepared in aqueous solution. And based on electrostatic interactions, the thiol-passivated AgI nanoparticles were assembled in a self-assembled film by alternative deposition with a cationic polyelectrolyte. Then the AgI nanoparticles in the composite film were reduced by NaBH4, which resulted in the formation of a thin film of Ag nanoparticles. UV-visible spectra and X-ray photoelectron spectroscopy data confirmed the transformation from AgI to Ag. Atomic force microscopy (AFM) showed that the formed Ag nanoparticles distributed on the film homogeneously. Surface-enhanced Raman spectroscopy (SERS) measurement indicated that the prepared thin films could be used as effective SERS substrates. The reduction process was also carried out by UV light at selective surface regions, which resulted in the formation of patterned nanoparticle arrays. [Copyright &y& Elsevier]