Sol-gel-processed inorganic oxides: organic polymer composites for second-order nonlinear optical applications

A new class of promising composite materials consisting of sol-gel processed inorganic oxides and organic polymers has been developed over the last several years. These materials have been shown to be homogeneous, mechanically stable and have excellent optical properties. Second-order nonlinear optical properties are dependent upon the active chromophore being aligned within the structure. We report here the studies on the second-order nonlinear optical properties of a new oxide:polymer composite. A second-order chromophore, (N,N- diethylamino-(B)-nitrostyrene or DEANST) has been doped into a sol-gel/polymer composite comprised of polyvinylpyrrolidone (PVP) and silica. The removal of solvent from a simple sol-gel preparation causes a tremendous shrinkage of the pores of the matrix. In addition, this particular polymer is capable of being crosslinked at elevated temperatures. These two effects were used to retain the alignment of the chromophores within this unique host material. The second-harmonic generation technique was used as a function of time to ascertain the utility of this approach and to determine the precise roles of processing conditions and components necessary to bring about this effect. The results of this work indicate that this composite can preserve the alignment of DEANST to satisfactory levels, making it an excellent candidate for device applications.