Erbium-activated silica–titania planar waveguides on silica-on-silicon substrates prepared by rf sputtering

Erbium-activated silica-titania planar waveguides were prepared by radio-frequency (rf) sputtering technique. Silica-on-silicon substrates obtained by plasma-enhanced chemical vapor deposition (PECVD) and rf sputtering (RFS) were employed. The refractive indices, the thickness and the propagation losses of the waveguides were measured. The refractive index and the roughness of the silica substrates produced by RFS appear to be dependent on the thickness. Thermal annealing, which is a necessary condition to obtain light propagation, induces a decrease of the refractive index in the silica substrates. The waveguide deposited on PECVD substrate exhibits several propagating modes with an attenuation coefficient 1.7 dB/cm compared with 12.2 dB/cm measured for the waveguide deposited on silica substrate produced by RFS technique. Emission of the 4I13/2->4I15/2 transition with a 53 nm bandwidth was observed.