Physics Seminar
Physics seminar Sept. 23 on “Lasting Media Based on Novel Vitreous Rare Earth Phosphates: High Energy X-Ray Diffraction and X-Ray Absorption Spectroscopy Studies”
A physics seminar on “Lasting Media Based on Novel Vitreous Rare Earth Phosphates: High Energy X-Ray Diffraction and X-Ray Absorption Spectroscopy Studies” will be held Friday, Sept. 23 from 2:30 to 3:20 p.m. in Hagen Hall 325. The speaker is Dr. Kanishka Marasinghe from the University of North Dakota.
High energy/power lasing media based on vitreous rare earth phosphates (VREPs) are the materials of choice for a wide range of applications including fusion energy research and directed energy weapons. However, lasing efficiency of REPG depends heavily on their atomic structure, especially the coordination environment of rare earth ions, which is highly dependent on many factors including concentration and type of are earth ions and processing conditions. We have studied the atomic-scale structure of a series of rare earth doped sodium phosphate glasses with compositions (R2O3)x(Na2O)y(P2O5)1-x-y where R = Nd, Eu and Dy, 0.04 < x < 0.13, and x + y ~ 0.4 using high energy X-ray diffraction (HEXRD) and X-ray absorption (XAS) techniques. Structural features such as inter-atomic distances and coordination numbers and their dependence on the concentration and type of the rare-earth ion have been obtained by analyzing pair and radial distribution functions. Emission spectra of these materials have also been measured. Our studies suggests that the [O]/[P] ratio of these materials is primarily responsible for dictating the coordination environment of rare earth ions. When this ratio is in the 2.9-3.0 range, rare-earth coordination environment undergoes a significant change. Emission spectra show that their florescence efficiency decreases with increasing rare-earth content even at relatively low concentrations (0.05 < x < 0.25) suggesting that concentration quenching of lasing action may be present even at these concentrations.