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We study the structural and infrared-to-visible upconversion fluorescence properties of Er3+/Yb3+-codoped lead-free germanium-bismuth glass. The structure of lead-free germanium–bismuth–lanthanum glass is investigated by peak-deconvolution of Raman spectroscopy. Intense green and red emissions centred at 525, 546, and 657 nm, corresponding to the transitions 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2, respectively, are observed at room temperature. The quadratic dependence of the 525, 546, and 657 nm emissions on excitation power indicates that a two-photon absorption process occurs under 975 nm excitation.

Frequency upconversion fluorescence property of Er3+-doped oxychloride germanate glass is investigated. Intense green and red emissions centred at 525, 546, and 657 nm, corresponding to the transitions 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2, respectively, were simultaneously observed at room temperature. The quadratic dependence of the 525, 546, and 657 nm emissions on excitation power indicates that a two-photon absorption process occurs under 975 nm laser diode (LD) excitation. The Raman spectrum investigation indicates that oxychloride germanate glass has the maximum phonon energy at ~805 cm−1. The thermal stability of this oxychloride germanate glass is evaluated by differential scanning calorimetry, and thermal stability factor ΔT (ΔT = Tx−Tg) is 187 degrees C. Intense upconversion luminescence and good thermal stability indicate that Er3+-doped oxychloride germanate glass is a promising upconversion laser material.

A tellurite fibre of TeO2–ZnO–La2O3–Li2O glass codoped with 20000 ppm ytterbium and 5000 ppm erbium was fabricated by the suction casting and rod-in-tube technologies. The absorption spectrum of Er3+/Yb3+ -codoped bulk glass has been measured. From the Judd–Ofelt intensity parameters, the spontaneous emission probability and radiative lifetime τrad of Er3+:4I13/2→4I15/2 transition for the bulk glass have been calculated. The emission fluorescence spectra and lifetimes around 1.5μm and subsequent upconversion fluorescence in the range of 500–700nm were measured in fibres and compared with those in bulk glass. The changes in amplified spontaneous emission with fibre length and pumping power was also measured. It was found that the emission spectrum from erbium in fibres is almost twice as broad as the corresponding spectrum in bulk glass when pumped at 980nm.

Erbium-doped TeO2-based oxysulfide glasses have been prepared in argon atmosphere in graphite crucibles. The results of thermal analysis and spectroscopic properties of Er3+ have been studied in terms of sulfide influence. As a function of composition, we have measured principally the optical absorption, spontaneous emission and lifetime of the materials. Judd–Ofelt theory was introduced to calculate bandwidth and emission cross-section of Er3+. The results demonstrate that addition of sulfide in tellurite glasses results in broad emission spectra, with high emission cross-section, slightly low emission lifetime and a comparatively high thermal stability as pure oxide glasses.

New oxyfluoride glasses and glass ceramics co-doped with Nd3+, Yb3+ and Ho3+ were prepared. The upconversion of infrared radiation into green fluorescence has been studied for Nd3+, Yb3+ and Ho3+ in the transparent oxyfluoride glass ceramics. At room temperature very strong green upconversion luminescence due to the Ho3+: (5F4, 5S2)→5I8 transition under 800 nm excitation was observed in the glass ceramics. The intensity of the green upconversion luminescence in a 1mol% YbF3-containing glass ceramic was found to be about 120 times stronger than that in the precursor oxyfluoride glass. The reason for the highly efficient Ho3+ upconversion luminescence in the oxyfluoride glass ceramics is discussed. The upconversion mechanism is also investigated.

New oxyfluoride glasses and glass ceramic codoped with Nd3+, Yb3+ and Ho3+ were prepared. The x-ray diffraction analysis revealed that the heat treatments of the oxyfluoride glasses could cause the precipitation of (Nd3+, Yb3+, Ho3+)-doped fluorite-type crystals. Very strong green up-conversion luminescence due to the Ho3+: (5F4, 5S2)→5I8 transition under 800-nm excitation was observed in these transparent glass ceramics. The intensity of the green up-conversion luminescence in a 1-mol% YbF3-containing glass ceramic was found to be about 120 times stronger than that in the precursor oxyfluoride glass. The reason for the highly efficient Ho3+ up-conversion luminescence in the oxyfluoride glass ceramics is discussed.

A complete set of spectroscopic parameters, including Judd-Ofelt parameters, radiative transition probabilities, radiative lifetime, branching ratios and integrated absorption cross section, have been calculated for Tm3+- doped fluoroaluminate (AYF) glass, based on the measured absorption spectra. The mechanism of Tm3+→Tm3+ and Yb3+Tm3+ energy transfers and fluorescence properties have been investigated in both Tm3+ single-doped and Yb3+/Tm3+ double-doped AYF glasses. The cross-relaxation process, 3F4+3H6→23H4, is proved, which makes the optimum Tm3+ concentration of 1.77µm fluorescence (3H4→ 3H6) much higher than 1.45µm fluorescence (3F4→ 3H4) in Tm3+:AYF glasses. In Yb3+/Tm3+:AYF glasses, a stronger concentration quenching is found for the 476nm emission than that for the 797nm emission and is discussed under the 970nm-excitation.

Three kinds of Er3+-doped tellurite glasses with different hydroxyl groups are prepared by the conventional melt-quenching method. Infrared spectra are measured to estimate the exact content of OH? groups in samples. The maximum phonon energy in glasses are obtained by measuring the Raman scattering spectra. The strength parameters ?t (t = 2,4,6) for all the samples are calculated and compared. The nonradiative decay rate of the Er3+ 4I13/2?4I15/2 transition are calculated for the glass samples with different phonon energy and OH? group contents. Finally, the effect of OH? groups on fluorescence decay rate of Er3+ is analysed, the constant KOH?Er of TWN, TZPL and TZL glasses are calculated to be 9.2?10?19?cm4s?1, 5.9?10?19?cm4s?1, and 3.5?10?19?cm4s?1, respectively.

The effects of F− ions in a germanium–lead–tellurite glass system on the spectral and potential laser properties of the Yb3+ are investigated. The absorption spectra, lifetimes, the emission cross-sections and the minimum pump intensities of the glass system with and without F− ions have been measured and calculated. The results show that the fluorescence lifetime and the minimum pump intensity of Yb3+ ions increase evidently, which indicates that germanium–lead–oxyfluoride tellurite glass is a promising laser host matrix for high power generation. FT-IR spectra were used to analyse the effect of F− ions on OH− groups in this glass system. Analysis demonstrates that addition of fluoride removes the OH− groups and results in improvement of fluorescence lifetime of Yb3+.

Novel Er3+ doped TeO2-based glasses containing PbS have been prepared in argon atmosphere in carbon crucibles. The thermal analysis and spectroscopic properties of those glasses have been considered in terms of sulfide influence. Judd–Ofelt theory is introduced to calculate the bandwidth and the emission cross-section. The results demonstrate that addition of PbS into tellurite glasses results in increasing bandwidth from 71.8 to 78.4 nm, for improving emission cross-section from 6.6 to 8.1×10−21 cm2 and slightly decreasing emission lifetime from 3.4 to 3.1 ms compared to pure oxide glass.

The upconversion properties of Tm3+/Yb3+-codoped lead chloride tellurite glass under 980 nm excitation were investigated. The intense blue (476 nm) emission and weak red (649 nm) emission corresponding to the 1G4→3H6 and 1G4→3H4 transitions of Tm3+ ions, respectively, were simultaneously observed at room temperature. The dependence of upconversion intensities on excitation power and the possible upconversion mechanisms are evaluated. The intense blue upconversion luminescence of Tm3+/Yb3+-codoped lead chloride tellurite glass can be used as potential host material for the development of blue upconversion optical devices.

We present the characterization of amplified spontaneous emission (ASE) from newly fabricated Er3+-doped tellurite fibres. When pumped at 980 nm, a very broad erbium ASE in the range 1450–1650 nm is observed. The changes of ASE with regard to fibre lengths and pumping power were measured. The output of 2 mW from an Er3+-doped tellurite fibre ASE source is obtained with the pump power of 540 mW.

New multi-component Yb:zinc–tungsten–tellurite glasses (70TeO2-(20-x) ZnO-xWO3-5La2O3-2.5 K2O-2.5 Na2O-1.0 Yb2O3 (x = 0, 15 mol%) have been presented. Thermal stability and spectroscopic properties of Yb3+ ions have been measured. The results show that TZW2 glass (x = 15 mol%) has thermal stability (Tx−Tg>160 degrees C with Tx being the onset crystallization temperature and Tg the glass transition temperature) better than TZN glass and that the stimulated emission cross-section of 1.32 pm2 for the 2F5/2→2F7/2 transition is higher than other laser glasses (QX, ADY, LY and FP), with the measured fluorescence lifetime of 0.93 ms and the broad fluorescence effective linewidth of 74.5 nm. Evaluated from the good potential laser parameters, TZW2 glass with both the minimum pump intensity (0.92 kW/cm2) and gain parameter (1.23 pm2ms) is promising for miniature solid fibre lasers or high-peak power lasers, as well as tunable lasers.