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Silica-titania sol-gel planar waveguides were deposited on silica glass disks by spin coating. Fluorescence lifetimes as high as 375 μs were measured in neodymium-doped sol-gel planar waveguides and 1.78 ms for an erbium-doped film. Quenching was found to occur for the former at concentrations above 1 at. % of neodymium.

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Abstract. Spin-coating is one of the possible methods for the fabrication of optical planar waveguides. These have several applications in integrated optical devices, provided that their optical losses are below ~1 dB/cm. The attenuation is caused in part by surface and bulk scattering. The latter depends on the microstructure of the films and, more particularly, the porosity, which is studied here. A series of SiO2-TiO2 films were prepared from solutions containing different concentrations of ethanol. The influence of the ethanol/(Si + Ti)alkoxides volume ratio on the porosity was investigated by Ellipsometry, Infrared Spectroscopy, and Scanning Electron Microscopy. The porosity volume fraction was found to reach a minimum when the ethanol volume ratio is near 4.