Contents I. Introduction
As optical networks are spreading towards the final customer and the need of compact, low-cost and rugged systems capable of regenerating the optical signal becomes evident, integrated optical amplification devices are gaining increasing interest. Ideally, compact optical amplifiers should have high gain, small size, low cooperative upconversion and low pump power. Hence, much work has been devoted to the development of the optical materials suitable for these tasks. Recently Er3+/Yb3+ co-doped phosphate glasses are popular gain materials for optical amplifiers due to their capability for emission of radiation at the wavelength region [1]. In order to improve optical characteristics and chemical durability of phosphate glasses, an enormous amount of research has been done by introducing glass formers and modifiers into phosphate glass host [2]. Due to the presence of heavy metal compounds in the glass matrix, it is expected that the refractive index is higher, which will result in the increase of the stimulated emission cross section and the broadening of the bandwidth at , then improves the optical characteristics of phosphate glasses. In the meanwhile, the presence of lead halides can also significantly increase the glass formation regions and glass stability against devitrification. These are very important for producing high quality waveguide.
