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Microstructural features of a new hybrid organoaluminosilicate glass are described. The glass is prepared by low temperature acid catalyzed hydrolysis and polycondensation of organoalkoxides. This sol-gel method produces transparent materials for one-step, crack-free thin film formation suitable for fabrication of passive and active optical waveguides. Aluminum NMR reveals that the inclusion of erbium ions affects the structure of the glass by controlling the distribution of aluminum between tetrahedral and octahedral coordination sites in the lattice. The distribution appears to follow the 'aluminum avoidance principle' enunciated by Lowenstein. We also find that choice of the erbium ion precursor markedly affects the structure of the glass. This was demonstrated by comparing Er3+ derived from the nitrate and the double alkoxide, Er[Al(isopropoxide)4]3. The latter compound, when mixed in pre-hydrolyzed organosiloxane media, forces aluminum to retain its tetrahedral coordination geometry. This is not so when erbium originates from the nitrate. Evidence from NMR, Raman and transmission electron microscopy suggests that the erbium ion is rather homogeneously dispersed in the glasses. This suggests that clustering of the rare earth may have been defeated in this system. Because the glass contains a photosensitive moiety, erbium-doped channel waveguides can be prepared by direct photoinscription.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. |
