Lisha Zhao

Electric-field-induced layer-by-layer fabrication of inorganic–organic hybrid second-order nonlinear optical films

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.

Electric-field-induced fabrication of covalently linked second-order nonlinear optical multilayer films on nonconductive substrates

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.