Erbium-activated silica-titania planar waveguides

(100 - x) SiO2-(x)TiO2-ErO3/2 planar waveguides, with 7 less than or equal to x less than or equal to 20 have been prepared by sol-gel route using the dip-coating technique. The thickness of the films was optimized to support a single propagating mode at 1550 nm, with a confinement coefficient higher than 0.75. The process of densification of the gel and the devitrification with the growth of TiO2 nanocrystals were studied by Raman scattering. Devitrification is important only for x greater than or equal to 15, but it was not possible to obtain full densification of the samples, even at the lowest TiO2 content, without the appearance of nanocrystals. Emission in the C telecom band was observed; the spectral width of the I-4(13/2)-->I-4(15/2) transition of Er3+ slightly increases with the titania content. For x less than or equal to 12 most of Er3+ ions (about 65%) decay exponentially with a lifetime of about 8 ms.