It is well known that the stimulated emission characteristics of RE ion depend on the surrounding host matrix in which the ions are incorporated. The surrounding ligand field can have a con- siderable influence on the optical absorption and stimulated emission cross-sections and fluorescence decay rates, hence, the quantum efficiency can be tuned for specific applications. The non-radiative processes include characteristic of the host and active ion concentration. Phosphate glass is an excellentmaterial for amplifier due to properties of good chemical durability, ion-exchan- geability, high gain coefficient, wide bandwidth capability, low up- conversion emission, high transparency, low melting point, low refractive index and low dispersion. Phosphate glass presents high solubility of RE ions allowing a high concentration of active ion into a small volume. Moreover, phosphate glasses have been proposed as laser hosts and solid state ionic conductors. However, if phosphate glasses are used as a laser ion host, they have drawbacks such as larger thermal expansion and lower fracture toughness than silicates.