Improved Composition for Sol-Gel Rare-Earth Doped Planar Waveguides

A multilayer sol-gel process has been developed in order to make highly doped rare-earth planar waveguides on silica or silicon substrates.Starting with a small range of constituents, such as SiO₂, TiO₂, P₂O₅ and Al₂O₃, we show that a large variety of gel compositions, with different spectroscopic behaviour, can be made when doped with rare-earths.We have doped the sol-gel films with neodymium and we have optimized their compositions by measuring the neodymium fluorescence lifetime. For a composition with 10 atom% of phosphorous, the lifetime evolution with neodymium concentration was studied and a quenching concentration was found at 1% of neodymium. We have also shown the strong influence of phosphorous or aluminium in the sol composition on the fluorescence lifetime, for a given neodymium concentration. First results on similar planar waveguides, doped with erbium, are also presented.The stability of the fluorescence lifetime over a long period of time is an other important point to be checked for these new materials: the lifetime evolution over a 9 months measurement period is presented.