Optical properties of SiO2-TiO2 thin film waveguides obtained by the sol-gel method and their applications for sensing purposes

Optical properties of silica-titania thin films prepared by the sol-gel technique are presented. The layers were deposited on glass slides or silica wafers by a dip coating process. Samples were prepared from different mixtures of silica and titania alkoxides. The stable, crack-free and transparent coatings were obtained after heating in the air at 60 °C and 500 °C. The layers coated on oxidized silica plates (on SiO2 optical substrate layers) can be used as planar waveguides. Coupling light into silica-titania thin films was possible by applying grating couplers. This functional device, fabricated by the holographic method, allows to couple laser light in and out of the planar waveguides by exciting various waveguide modes. The possibility of using silica-titania thin films with entrapped sensing molecules as an optical waveguide sensor is also discussed.