Nanostructured Er3+-doped SiO2–TiO2 and SiO2–TiO2–Al2O3 sol–gel thin films for integrated optics

Abstract The nanostructured multilayer silica–titania or silica–titania–alumina films doped with Er3+ were prepared by sol–gel method. The sol–gel method is a flexible and convenient way to prepare oxide films on several types of substrates, and for this reason it was extensively investigated for optical waveguides fabrication. The selected molar composition was 90%SiO2–10%TiO2 or 85%SiO2–10%TiO2–5% Al2O3 and 0.5% Er2O3. The films were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Spectroellipsometry (SE), as well as by Atomic Force Microscopy (AFM) and photoluminescence (PL). The films deposited on Si/SiO2 substrate by dip-coating or spin-coating, followed by annealing at 900 °C, presented homogenous and continuous surface and good adherence to the substrate. Differences were noticed in the structure and properties of the prepared films, depending on the composition and the number of deposited layers. Channel optical waveguides were obtained by patterning Er3+-doped SiO2–TiO2 and SiO2–TiO2–Al2O3 sol–gel layers deposited on oxidized silicon wafers.