J. Phys. IV France 04 (1994) C4-341-C4-344
Fluorescence of Eu3+ ions in TiO2 optical planar waveguides fabricated by the sol-gel methodM. BOUAZAOUI1, M. BAHTAT2, A. BAHTAT3 and J. MUGNIER3
1 Laboratoire de Spectroscopie Hertzienne, URA 249 du CNRS, Université Lille I, Bât. P5, 59655 Villeneuve d'Ascq, France
2 Laboratoire du Traitement du Signal et Instrumentation, URA 842 du CNRS, Faculté des Sciences, 23 bd du Dr. P. Michelon, 42023 Saint-Etienne, France
3 Laboratoire de Physico-Chimie des Matériaux Luminescents, URA 442 du CNRS, Université Lyon I, 43 Bd du 11 Novembre 1918, 69622 Villeurbanne, France
In recent years, rare-earth-doped optical planar waveguides have attracted considerable attention owing to their potential use in the field of integrated optics. To this end, several processes have been employed to produce rare-earth-doped waveguides. Here, we report on the fluorescence of europium trivalent ions in TiO2 planar waveguides fabricated by using the sol-gel method and the dip-coating procedure. 2-mol % Eu3+ : TiO2 films were deposited on optically polished pyrex substrates. These films are 80 nm thick and their refractive index is ranging from 1.8 to 2.1 depending on the annealing temperature (100°C-600°C). The fluorescence of Eu3+ ions was obtained by the excitation in the 5D2 level with an Argon ion laser (wavelength = 465.8 nm). At room temperature, the fluorescence spectra were recorded for different annealing temperatures. A correlation was seen between the luminescence spectra and the structural evolution of the gel network. Indeed, it was observed that heat treatment increases the Stark splitting which partially removes the transitions J-degeneracy, indicating that Eu3+ ions occupy low-symmetry sites and are more embedded in the TiO2 gel (densification of the TiO2 gel). Furthermore, it was observed that increasing the annealing temperature entails a high frequency shift and a broadening of the [MATH] transition, which shows that Eu3+ ions occupy more distorted sites. these observations are in good agreement with results obtained by waveguide Raman spectroscopy.
© EDP Sciences 1994