Fabrication by rf-sputtering processing of Er3+/Yb3+-codoped silica-titania planar waveguides

Er3+/Yb3+-codoped 92SiO2-8TiO2 planar waveguides, with 1.2 mol% Er and molar ratio Er/Yb of 2, were fabricated by rf-sputtering technique. The active films were deposited on silica-on-silicon and v-SiO2 substrates. The parameters of preparation were chosen in order to optimize the waveguides for operation in the NIR region with particular attention to the minimization of the losses. The thickness of the waveguides and the refractive index at 632.8 and 543.5 nm were measured by an m-line apparatus. The losses, for the TE0 mode, were evaluated at 632.8 and 1300 nm. The structural properties were investigated with several techniques such as Secondary Ion Mass Spectrometry, Energy Dispersive Spectroscopy and Raman Spectroscopy. All waveguides were single-mode at 1550 nm. An attenuation coefficient of 0.5 dB/cm at 632.8 nm and 0.1 dB/cm at 1300 nm were measured. The emission of 4I13/2 -> 4I15/2 of Er3+ ion transition with a 40 nm bandwidth was observed upon excitation at 981 and 514.5 nm in the TE0 mode. Back energy transfer from Er3+ to Yb3+ was demonstrated. Photoluminescence excitation spectroscopy was used to obtain information about the effective excitation efficiency of Er3+ ions by co-doping with Yb3+ ions.