Optical and fluorescent properties of Y2O3 sol–gel planar waveguides containing Tb3+ doped nanocrystals

Terbium doped Y2O3 planar waveguides were fabricated by sol–gel process and dip-coating using yttrium acetate as precursor. Two different doping modes were compared, i.e. introduction in the sol of dispersed Tb3+ions from dissolved Tb(NO3)3, or of nanoparticles of Tb2O3 or [Y2O3:50% Tb] from an alcoholic suspension. The chemical and nanostructural properties were analyzed by infrared spectroscopy, transmission electron microscopy and X-ray diffraction. The Tb3+ fluorescence properties were studied as a function of temperature and atmosphere of the thermal treatments, and of the Tb3+ concentration. The fluorescence properties are discussed in relation to the quenching mechanisms induced by Tb4+ transformation, residual OH groups, and crystallites size and structure. Optical propagation losses of the Tb doped Y2O3 planar waveguides related to the doping modes and Tb3+ concentration are presented. Doping sol–gel films by nanoparticles is shown to be a valuable alternative to the conventional doping from dissolved terbium salt.