Although the success of demonstrating tellurite glass as a waveguide material in many applications, including tellurite fiberization, Nd<sup>3+</sup>-doped tellurite fiber laser, and 1.5 μm ultra-broad band Er<sup>3+</sup>-doped optical amplifier, the advance of tellurite is still necessary in the areas of improving the quality of waveguide and understanding the correlations among processing, structure, and desired property, such as nonlinearity, rare-earth spectroscopy, nanocrystalline doping, and microstructured holey fiber. In the paper, we report some initial experimental results on fiberization processing of KNbO<sub>3</sub>-Na<sub>2</sub>O-ZnO-TeO<sub>2</sub> and Er<sub>2</sub>O<sub>3</sub>-WO<sub>3</sub>-TeO<sub>2</sub> systems. The report, in particular, focuses on the thermal characteristics of these glasses.
There is strong need for low cost, optically active materials whose high electro-optic (EO) and second harmonic generation (SHG) properties can be engineered flexibly, in bulk and fiber forms. Therefore, we have fabricated transparent ferroelectric composites consisting of strontium barium niobate crystallites in a refractive index compatible tellurium oxide (TeO<sub>2</sub>) glass matrix. Several glass compositions, in the series x SrO-(10-x) BaO-y (Nb<sub>2</sub>O<sub>5</sub>)-(90-y) TeO<sub>2</sub> (where x=2.5, 5 and 7.5 and y = 10, 15, 20 and 25), have been prepared by a conventional melt quenching technique. The compositions have been selected on the basis of thermal stability data obtained from differential thermal analysis (DTA). X-ray diffraction studies indicate ferroelectric phase formation in the controlled crystallized glasses. The non-centrosymmetric nature of the crystallized regions has been monitored via observing the second harmonic signal.