Erbium-activated monolithic silica xerogels and silica-titania planar waveguides: Optical and spectroscopic characterization

Recent results obtained for Er2O3-SiO2 monolithic xerogels and erbium activated SiO2-TiO2 planar waveguides are presented. Monolithic erbium-activated silica xerogels with erbium content ranging from 0 up to 40000 ppm were prepared by the sol-gel technique. Samples were densified by thermal treatment in air at 950 °C for 120 hours. The densification degree and the relative content of hydroxyl groups were studied by NIR absorption and Raman spectroscopies. Emission at 1.5 ?m. characteristic of the 4I13/2-> 4I15/2 transition of Er3+ ions, was observed at room temperature for all monolithic samples upon continuous wave excitation at 980 nm. For the 5000 Er/Si ppm doped xerogel, an intense photoluminescence was observed with a lifetime of 8 ms for the metastable 4I13/2 level. Passive and erbium-activated SiO2-TiO2 planar waveguides, monomode at 632.8 nm, were prepared by a dip-coating technique. Some parameters such as H2O content, intermediate and final thermal treatments, and the molar ratio TiO2/SiO2 were modified during the preparation of the solution m order to minimize the final content of residual hydroxyl groups and the phase separation between silica and titania. Raman spectroscopy was used to check the structural properties of the waveguides. A lifetime of 7 ms was measured'for the metastable 4I13/2 level in a 93SiO2-7.TiO2 planar waveguide activated by 10 000 ppm Er(Si+Ti). The best value of the attenuation coefficient was of 0.5 dB/cm at 632.8 nm.