Investigation of Er3+ coordination in zinc-lead tellurite bulk glasses and silica-hafnia glass ceramics waveguides

We present a comparison of the local structure of erbium in zinc-lead tellurite glasses and in silica-hafnia glass ceramics waveguides prepared using the melt quenching or sol-gel and dip coating techniques respectively. The local environment of Er3+ions was probed using the extended x-ray absorption fine structure (EXAFS) at the L3-edge of erbium at room temperature. Significative differences in the first Er-O coordination shells are evidenced. In tellurite glasses, independently on the ZnO/PbO content, the erbium co-ordination number (N) is constant at about 6.5, the distance (R) remains the same at 2.34 A and the Debye-Waller (σ2) is about 0.0150 A2. On the other hand, N is lower at about 5.2 for all the silica-hafnia waveguides, whereas the Er-O distance and the DW factors are changed with time and temperature of thermal annealing.