TiO₂/SiO₂/ORMOSIL hybrid material planar waveguides prepared at low temperature by sol-gel processing

We report the preparation of sol-gel derived planar waveguides from high titanium content hybrid materials. By incorporating organic molecules into the inorganic TiO₂-SiO₂ sol-gel glass matrix, porous-free waveguide films are obtained with low temperature heat treatment. The single spin-on thickness is measured to be more than 1.7 μm, enough to support light guiding and the refractive index of the film is found to depend on the heat treatment temperature. We also studied the microstructural and optical properties of the waveguide films using atomic force microscopy, ellipsometry, thermal gravimetric analysis, and UV-visible spectroscopy. Based on these experimental results, we found that heat-treatment at a temperature about 100°C is sufficient to produce a relatively dense film with high transmission in the visible and near infrared range. We believe that this process is very useful for the fabrication of passive photonic circuits on temperature sensitive substrates such as III-V compound semiconductors. Meanwhile, it has also been noted that a purely inorganic and crack-free silica-titan films could be obtained after baking the hybrid material film at 500°C or higher.