Department of Physics

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MS student Suman Rijal's Thesis Defense on June 9, 2017

May 22, 2017

THESIS DEFENSE
Speaker: Suman Rijal
Date: Friday, June 9
Time: 2:00 pm
Room: Currens Hall 336

Effect of Host Glass and Semiconducting Nanoparticles on the Optical Properties of Rare Earth Ions in Lead/Bismuth Telluroborate Glasses

Abstract:

The optical properties of rare earth ions (RE) Sm3+ in bismuth telluroborate and lead telluroborate glasses are studied as a function of glass composition with Bi2O3 content (29.5 to 59.5 mol%) and PbO (29.5 to 49.5 mol%). We also studied the effect of semiconducting nanoparticle CdSe on the absorption and fluorescence emission of Sm3+ in both bismuth and lead telluroborate glasses for different annealing hours (3 to 26 hrs.). Optical absorption is used to calculate the absorption coefficient and the number density of rare-earth (RE) ions is calculated from the measurement of the glass density. Optical absorption and fluorescence spectra of these RE doped bismuth and lead telluroborate glasses are analyzed using Judd-Ofelt theory. The compositional dependence of Judd-Ofelt intensity parameters, ©_t (t=2,4,6,) are determined and then used to calculate the radiative transition probability of the excited states, the total radiative transition probability, branching ratios, and radiative lifetime of the glasses. These intensity parameters represent changes in the symmetry of the ligand field at the Sm3+ site (due to structural group changes and changes in Sm-O covalency). From the fluorescence spectra, obtained using 404 and 488 nm excitation wavelength, the stimulated emission cross-section of the excited states is calculated as a function of glass composition. In all the glass systems studied, it is found that the optical properties are strongly influenced by structural changes arising from compositional variation and size of nanoparticles. The color coordinates corresponding to the prominent emissions of the glass samples are determined by using the CIE Color Matching Function Calculator. The purity of these colors is also measured using the CIE color coordinate diagram. The emission color for our glass samples lies at the edge of white and orange.

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