Raman and optical absorption spectroscopic investigation of Yb-E...

Yb-Er codoped Na2O-Al2O3-P2O5-xSiO2 glasses containing 0-20 mol% SiO2 were prepared successfully. The addition of SiO2 to the phosphate glass not only lengthens the bond between P^{5+} and non-bridging oxygen but also reduces the number of P=O bond. In contrast with silicate glass in which there is only four-fold coordinated Si^{4+}, most probably there coexist [SiO4 tetrahedron and [SiO6] octahedron in our glasses. Within the range of 0-20 mol% SiO2 addition, the stimulated emission cross-secti