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

Two 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 silica glass substrates. 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 by 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 at 1530 nm of the 4I13/2 → 4I15/2 transition of Er3+ ion was observed at room temperature upon continuous wave excitation at 981 and 514.5 nm. Back energy transfer from Er3+ to Yb3+ was demonstrated by measurement of Yb3+ emission upon Er3+ excitation at 514.5 nm. Effective excitation efficiency of Er3+ ions by co-doping with Yb3+ ions was shown by photoluminescence excitation spectroscopy.