Er3+/Yb3+-activated silica titania planar waveguides for EDPWAs fabricated by rf-sputtering

Er3+/Yb3+-codoped silica titania planar waveguides, with 1 mol% Er and molar ratio Yb/Er of 2, were fabricated by rf-sputtering technique. The active films were deposited on silica-on-silicon substrates, obtained by plasma-enhanced chemical vapor deposition, and v-SiO2. Sputtering deposition was performed by using a 4" silica target, TiO2 discs and pieces of metallic ytterbium and metallic erbium. Various parameters of preparation were varied in order to optimize the waveguides for operation in the NIR region with particular attention to the minimization of the losses and the increasing of the luminescence efficiency of the metastable 4I13/2 state of the Er3+ ion. After thermal annealing at 600°C for 6 hours the waveguides exhibited several well confined TE and TM propagating modes at 633 nm and one mode at 1550 nm. The thickness of the waveguides and the refractive index at 632.8, 543.5 nm and 1300 nm were measured by an m-line apparatus. The losses, for the TE0 mode, were evaluated by photometric detection of the light intensity scattered out of the waveguide plane and an attenuation coefficient of 0.5 dB/cm at 632.8 was measured. The structural properties were investigated with several techniques such as SIMS, EDS and Raman. Waveguide luminescence spectroscopy was used to study the 4I13/2 --> 4I15/2 transition of Er3+ ion. The emission at 1530 nm was observed at room temperature upon continuous wave excitation at 978 nm with a spectral width of the emission band of 37 nm. A lifetime of 7.2 ms for the metastable 4I13/2 level was measured.