Raman and optical absorption spectroscopic investigation of Yb-Er codoped phosphate glasses containing SiO_2

Yb-Er codoped Na_2O-Al_2O_3-P_2O_5-xSiO_2 glasses containing 0-20 tool% SiO_2 were prepared successfully. The addition of SiO_2 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 SiO_4] tetrahedron and SiO_6] octahedron in our glasses.Within the range of 0-20 tool% SiO_2 addition,the stimulated emission cross-section ...