TiO2-based thin films for photonics

The use of the sol-gel process to produce optical planar waveguide is attracting considerable interest. In this work we present the preparation and characterization of Er-doped waveguide based on SiO2-TiO2 system. (100-x)SiO2-(x)TiO2-0.5Er2O3 planar waveguides, with 7?x?20 have been prepared by sol-gel route using the dip-coating technique. The thickness of the films was optimized to support a single propagating mode at 1550 nm, with a confinement coefficient higher than 0.75. The process of densification of the gel and the devitrification with the growth of TiO2 nanocrystals were studied by Raman scattering and X-ray diffraction. Devitrification is important only for x?15. However, even at the lowest TiO2 content the presence of nanocrystals was detected after full densification of the samples. Emission in the C telecom band was observed; the spectral width of the 4I13/2?4I15/2 transition of Er3+ slightly increases with the titania content. For x?12 most of Er3+ ions decay exponentially with a lifetime of about 8 ms.