Enhanced spectroscopic properties at 1.5 mm in Er3+/Yb3+-activated silica-titania planar waveguides fabricated by rf-sputtering

Two Er3+/Yb3+-codoped 94SiO(2)-6TiO(2) planar waveguides were fabricated by the rf-sputtering technique. One sample was doped with I mol% Er and the other was also doped with ytterbium, with a molar ratio Yb/Er = 2. The thickness and the refractive index of the waveguides were measured by an m-line apparatus operating at 632.8 and 543.5 nm. 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 1300 and 1550 nm. An attenuation coefficient of 0.5 dB/cm at 632.8 nm and a lifetime of the I-4(13/2) metastable state of 7.2 ms were measured. Upon cw excitation at 978 nm, an increase of the 1.53 mum luminescence intensity larger than two-fold was detected in the Yb3+/Er3+-codoped waveguide with respect to the waveguide doped only with Er3+.