Intense Frequency Upconversion Emission of Rare Earth Codoped Lead Bismuth Gallium Borate Glasses

Abstract

In order to develop efficient upconversion laser materials in the visible region an active lead borate matrix codoped with Tm3+/Yb3+ rare earth ions has been studied extensively. Optical absorption, DSC, FTIR and photoluminescence spectra of these glasses have been studied. Judd-Ofelt theory has been applied to the f ↔ f transitions for evaluating Ω2, Ω4 and Ω6 parameters. Radiative properties like branching ratio βr and the radiative life time τR have been determined on the basis Judd–Ofelt theory. Taking advantage of the high absorption transition probability of the Yb3+ ions, these ions are excited with 980 nm radiation from a commercial laser diode and subsequently de-excited by efficiently transferring energy to the Tm3+ ions. The spectra exhibited two emission bands centered at 468 nm and 654 nm due to 1G4 →3H6 and 1G4 → 3H4 transitions, respectively. The results obtained are discussed quantitatively based on the energy transfer between Yb3+ and Tm3+. Comparing the obtained values to those reported in other Tm3+/Yb3+ doped materials, the lead bismuth gallium borate glasses doped with 0.2 mol% of Yb2O3 ions 0.6 mol% of Tm2O3 can be considered excellent candidates for developing blue upconversion laser materials in the visible region.