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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]

Abstract: Relative to the Er3+:gold-nanoparticle (Er3+:Au–NP) axis, the polarization of the gold nanoparticle can be longitudinal (electric dipole parallel to the Er3+:Au–NP axis) or transverse (electric dipole perpendicular to the Er3+:Au–NP axis). For longitudinal polarization, the plasmon resonance modes of gold nanoparticles embedded in Er3+-doped germanium–tellurite glass are activated using laser lines at 808 and 488nm in resonance with radiative transitions of Er3+ ions. The gold nanoparticles were grown within the host glass by thermal annealing over various lengths of time, achieving diameters lower than 1.6nm. The resonance wavelengths, determined theoretically and experimentally, are 770 and 800nm. The absorption wavelength of nanoparticles was determined by using the Frohlich condition. Gold nanoparticles provide tunable emission resulting in a large enhancement for the 2H11/2 → 4I13/2 (emission at 805nm) and 4S3/2 → 4I13/2 (emission at 840nm) electronic transitions of Er3+ ions; this is associated with the quantum yield of the energy transfer process. The excitation pathways, up-conversion and luminescence spectra of Er3+ ions are described through simplified energy level diagrams. We observed that up-conversion is favored by the excited-state absorption due to the presence of the gold nanoparticles coupled with the Er3+ ions within the glass matrix. [Copyright &y& Elsevier]

Abstract: We report a systematic study of the localized surface plasmon resonance effects on the photoluminescence of Er3+-doped tellurite glasses containing Silver or Gold nanoparticles. The Silver and Gold nanoparticles are obtained by means of reduction of Ag ions (Ag+ →Ag0) or Au ions (Au3+ →Au0) during the melting process followed by the formation of nanoparticles by heat treatment of the glasses. Absorption and photoluminescence spectra reveal particular features of the interaction between the metallic nanoparticles and Er3+ ions. The photoluminescence enhancement observed is due to dipole coupling of Silver nanoparticles with the 4I13/2 → 4I15/2 Er3+ transition and Gold nanoparticles with the 2H11/2 → 4I13/2 (805nm) and 4S3/2 → 4I13/2 (840nm) Er3+ transitions. Such process is achieved via an efficient coupling yielding an energy transfer from the nanoparticles to the Er3+ ions, which is confirmed from the theoretical spectra calculated through the decay rate. [Copyright &y& Elsevier]

Abstract: Processes of energy transfer in Er3+–Tm3+ co-doped tellurite glasses has permitted to obtain an expanding broadband emission in the near-infrared region covering the bands S, C+L and U of the optical telecommunications and extending up to the 1700–1900nm range under excitation by a 976nm laser diode. This widening of the emission band is achieved through an integrated emission, where the Er3+ ions act as donor and the Tm3+ ions as acceptor following the route (Er3+)4I11/2→(Tm3+)3H5, (Er3+)4I13/2→(Tm3+)3H4 and (Er3+)4I13/2→(Tm3+)3F4. The relative intensity emission and lifetime of the 4I13/2→4I15/2 transition of the Er3+ ions decrease with increasing the Tm3+ concentration. Besides, high Tm3+ concentrations produce an emission quenching for the 3H4→3F4 and 3F4→3H6 radiative transitions, due to cross-relaxation between Tm3+ ions. These effects are studied by means of probability and quantum yield of the energy transfer. The most intense and widest emission band is measured in the glass co-doped with 0.075 and 1mol% of Tm2O3 and Er2O3, respectively. [Copyright &y& Elsevier]