Sol–gel planar waveguides for integrated optics

Abstract Er 3+ -doped silica–titania based planar waveguides with a composition 72SiO 2 –18TiO 2 –9AlO 1.5 – x ErO 1.5 – y YbO 1.5 (in mol%) have been prepared by sol–gel processing, using multilayer spin-coating deposition on silica glass or silica-buffered single crystal Si substrates. Their optical properties were measured, including the measurement of the refractive index at 633 nm by ellipsometry, the optical loss by prism coupling at different wavelengths and the Er 3+ fluorescence spectra and lifetimes at 1.54 μm. The optical loss at 633 nm varied from ca. 0.7 to 1.0 dB/cm, the Er 3+ emission at 1.54 μm had a full width at half maximum of ∼55 nm and the corresponding lifetimes varied between 3 and 6 ms, depending on the Er concentration and the residual OH level in the films, which was estimated by FTIR to be less than 200 ppm in the best cases.