Novel organometallic nanomaterials exhibiting high nonlinearities including photorefraction at telecommunication wavelengths

Novel unique organometallic nanomaterials with high nonlinearities of various types (nonresonant, resonant, photorefractive) have been prepared. Two main kinds of nanomaterials actualizing the different nonlinear-optical processes have been created: 1) polymeric photorefractive nanocomposites with very low glass transition temperatures (ca. 8 deg C) based on poly[ethynediyl-arylene-ethynediyl-silylene]s and sensitive in the visible (633 nm) and near-infrared region (1000-1500 nm) have been developed. The TEM investigations of the composite thin films have revealed self-oganized lamellar structures. The red shift of the absorption spectra and the appearance of a long absorption tail in the near IR region in the case of the films (unlike the solutions) confirm the essentially pi-stacking mechanism in the formation of the supramolecular assembly. The mechanism of self-organization into lamellar phases is discussed. 2) chromium-containing polymeric nanocomposites of high optical and mechanical quality have been prepared. They contain bis-arenechromium complexes covalently bonded to polyacrylonitrile macrochains. The conditions of film-casting give rise to the formation of conjugated polynaphthyridine-type structures inside the polymeric matrix as a result of cyclization of the acrylonitrile units. In addition, the TEM investigations of the films showed that nanosize particles (20-30 nm), containing chromium are formed in the material. These materials exhibit record Kerr-type cubic nonlinearities (chi3 = -2.5×10 -10 esu) suggesting a pi-stacking mechanism giving rise to self-organized supramolecular structures. Our theoretical calculations show that the level of nonresonant optical nonlinearity should in principle allow actualizion of fast optical switching with speeds suitable for modern optical connection systems (100 Gbit/s).