Er3+/Yb3+ activated silica-hafnia planar waveguides for photonics fabricated by rf-sputtering

Er3+/Yb3+-codoped 95.8 SiO2 - 4.2 HfO 2 planar waveguide was fabricated by the rf-sputtering technique. The sample was doped with 0.2 mol% Er and 0.2 mol% Yb. The thickness and the refractive indices of the waveguide were measured by an m-line apparatus operating at 543.5, 632.8, 1319 and 1542 nm. The losses, for the TE0 mode, were evaluated at 632.8, 1319 and 1542 nm. The structural properties were investigated with energy dispersive spectroscopy and Raman spectroscopy. The waveguide had a single-mode at 1.3 and 1.5 ?m and an attenuation coefficient of 0.2 dB/cm at 1.5 ?m was obtained. The emission of 4I 13/2 -> 4I15/2 of Er3+ ion transition with a 42 nm bandwidth was observed upon excitation in the TE 0 mode at 980 and 514.5 nm. The 4I13/2 level decay curves presented a single-exponential profile, with a lifetime of 4.6 ms. Back energy transfer from Er3+ to Yb3+ was demonstrated by measurement of Yb3+ emission upon Er3+ excitation at 514.5 nm. Photoluminescence excitation spectroscopy was used to obtain information about the effective excitation efficiency of Er3+ ions by co-doping with Yb ions. Channel waveguides in rib configuration were obtained by etching the active film by a wet etching process. Scanning Electron Microscopy was used to analyze the morphology of the waveguides.