This work reports on the preparation of erbium and ytterbium co-doped SiO 2 :HfO 2 single mode planar waveguides using the sol-gel method. Silica nanoparticles were prepared from tetraethylorthosilicate in basic media and the films were characterized by transmission electron microscopy, scanning electron microscopy, mechanical profilometry, M-lines spectroscopy based on prism coupling technique, X-ray diffractometry, infrared spectroscopy and photoluminescence spectroscopy. The film thicknesses and the refractive indexes were adjusted in order to satisfy a future efficient coupling to single mode optical fiber. Films suitable for both weak and strong light confinement were prepared varying hafnia concentration into the silica matrix . The lifetime values of erbium 4 I 13/2 state were measured in order to investigate the influence of clustering and hydroxyl groups on the fluorescence quantum efficiency of the 4 I 13/2 level, responsible for the emission at 1.55 lm attributed to the 4 I 13/2 ! 4 I 15/2 transition. The high lifetime values suggest the absence of erbium clusters and the elimination of hydroxyl groups by rapid thermal process.