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A detailed study of the spectroscopic properties of PbF2+GeO2+WO3 glass ceramics doped with Tm3+ and codoped with Tm3+ and Yb3+ ions upon 680 nm dye laser light excitation has been made. The absorption, up-conversion emission, excitation, and time-resolved spectra were measured as a function of TmF3 and YbF3 concentrations at room temperature. An enhancement of blue emission centered at 478 nm in the codoped sample was observed. The optium concentrations of TmF3 and YbF3 for this blue emission are about 0.2 and 15 mol %, respectively. It is suggested that the results are due to energy transfer between Yb3+ and Tm3+ ions. Measured oscillator strengths and radiative rates for several transitions are compared with calculated values using the Judd–Ofelt theory with reasonable agreement between theory and experiments for sample doped with Tm3+ ions.

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