Non-radiative relaxation in Ta-doped silica fibres

We describe the properties of tantalum-doped silica fibers which have been doped with thulium and produced by a normal solution doping technique. In silica fibers, non-radiative decay almost quenches luminescence from several of the Tm levels, notably the 3F4 level at 800 nm, and the 1H4 level at 2µm. The properties of these levels are a sensitive test of multiphonon decay rates in the host. We observe fluorescence decay components from these levels in Tm-doped tantalosilicate fibers which are significantly longer than those observed in Tm-doped germanosilicate or aluminosilicate fibers. This is interpreted as the formation of a low-vibrational-energy microenvironment around the rare earth