Extended X-ray Absorption Fine Structure (EXAFS) Analysis of Novel High Laser Media

Rare earth-doped phosphate glasses are useful for a variety of optical and optoelectronic applications including high energy/high power ($\sim $10$^{15}$ watt) Lasers. Binary (R$_{2}$O$_{3})_{x}$(P$_{2}$O$_{5})_{1-x}$ glasses can be prepared in the compositional range 0 $\le $ x $\le \quad \sim $0.30. Atomic-scale structure, especially the coordination environment of R$^{3+}$ ions, play a major role in determining optical/physical characteristics. We have investigated the R$^{3+}$ local environment of Praseodymium and Neodymium ultraphosphate and meta phosphate(REMP) glasses using extended X-ray absorption fine structure technique. For both Nd and Pr phosphate glasses, nearest neighbor (oxygen) coordination decreases with increasing RE concentration. For the first oxygen shell the RE-O distance ranges between 2.38-2.40 {\AA} and 2.39-2.46 {\AA} for Nd and Pr respectively. The second co-ordination shell around the RE ions consists of phosphorus ions, with RE-P distance about 3.4-3.5 {\AA} and co-ordination numbers ranging from 1.5 to 3. There exists an Oxygen shell (third shell) about 4.1 {\AA} from RE ion for both Nd and Pr phosphate glasses.