Photoluminescence of erbium-doped silicate sol-gel planar waveguides

Er3+-doped silica-titania planar waveguides, prepared by sol-gel processing, have a tendency to exhibit a reversible photoluminescence (PL) quenching phenomenon at 1.5 ?m, when they are not fully densified. In the present paper, the presence of porosity and OH species associated with a simultaneous decrease in the Er3+ PL intensity and lifetime are followed in detail by infrared and m-line spectroscopies. Different chemical compositions and EtOH/precursor ratios, as well as optimized heat treatments, have been used in order to ensure the preparation of fully densified waveguides with enhanced spectroscopic properties. Both the Er3+ PL spectra and the fluorescence lifetimes at 1.5 ?m have been determined in the SiO2-TiO2-AlO1.5-ErO1.5, SiO2-HfO2-AlO1.5-ErO1.5 and SiO2- HfO2-TiO2-AlO1.5-ErO1.5 systems, as a function of the matrix composition and Er3+ ion concentration. These waveguides, densified at 900oC, appear to offer the best performance in terms of stability and strength of the PL signal.