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Optical properties of a neodymium (Nd3+) doped glass having composition based on the (Ga2S3)–(GeS2) system are reported. Transition probabilities, radiative lifetimes, and branching ratios related to Nd3+ levels were determined. Frequency upconversion (UC) luminescence due to nonresonant excitation at 1064 nm was observed at ≈535, ≈600, and ≈670 nm. The dependence of the UC intensity on the laser intensity and on the Nd3+ concentration as well as the dynamics of the luminescence process were studied. The results indicate that two-photon absorption by isolated Nd3+ ions and energy transfer among pairs of Nd3+ ions contribute to the UC luminescence. [ABSTRACT FROM AUTHOR]

Abstract: The luminescence properties through up-conversion emission process of Er3+–Tm3+-codoped germanium–tellurite glasses was carefully investigated by using UV–visible–near-infrared absorption spectroscopy, emission spectroscopy and lifetime measurement under near-infrared laser diode excitation at 976nm. The glass samples were prepared by the conventional melt-casting technique. The Er3+ and Tm3+ ions act in this glass matrix as donor and acceptor, respectively, and can generate under 976nm laser excitation a visible emission tunable from the green to the red color by varying the Tm3+ ion concentration. Two mechanisms are involved to obtain this up-conversion emission and its tunability from the green to the red light: (i) the excited state absorption (ESA) of Erbium ions Er3+:(4I11/2 → 4F7/2) and; (ii) the energy transfers (ETs) between Erbium Er3+ and Thulium Tm3+ ions. Such processes were studied by means of quantum efficiency and ET probability. It was verified that both of them depend on the Tm3+ ion concentration. The relative intensity of the red emission was increased up to 2.6 times for the glasses containing 0.1mol% and 1.0mol% of Thulium oxide Tm2O3 if compared with the Erbium Er3+ single doped glass. The spectroscopic study presented in this work has permitted to fully describe the color rendering, ranging from green to red through yellow and orange, of the light emitted by the Er3+–Tm3+-codoped germanium–tellurite glasses under a low power laser diode excitation at 976nm (30mW). [Copyright &y& Elsevier]