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Nd 3+ was introduced into Er 3+ doped tellurite glass with composition of TeO 2 Nb 2 O 5 ZnO Na 2 O to improve the 2.7 μm band fluorescence upon the excitation of 800 nm LD. The DSC curve and Raman spectrum were measured to characterize the thermal stability and vibration nature of glass host. The absorption spectra, visible, near- and mid-infrared fluorescence emission spectra were measured to evaluate the effects of Nd 3+ introduction on the spectroscopic properties especially the 2.7 μm band fluorescence of Er 3+ . It is shown that the prepared tellurite glass exhibits a large glass transition temperature and no obvious crystallization peak is observed in the measured temperature range of 200–550 °C. Moreover, the introduction of Nd 3+ significantly improves the 2.7 μm band fluorescence intensity through joint energy transfer processes between the relevant excited levels of Er 3+ and Nd 3+ , and the energy transfer mechanisms are further investigated in detail by calculating energy transfer micro-parameters and efficiency. The excellent thermal stability and strong 2.7 μm fluorescence emission aroused by adopting codoping scheme indicate that the prepared Er 3+ /Nd 3+ codoped tellurite glass is a potential glass medium applied for the 2.7 μm mid-infrared band lasers. [ABSTRACT FROM AUTHOR]

Highlights: [•] Tm3+/Ho3+/Yb3+ codoped tellurite glasses were prepared using melt-quenching method. [•] The structure behavior, thermal stability and multicolor emission were investigated. [•] The thermal stability of prepared glass increased with rare-earth doped concentration. [•] The multicolor emission was demonstrated by adjusting rare-earth doped concentration. [•] The quantitative study of phonon-assisted energy transfer mechanism was presented. [ABSTRACT FROM AUTHOR]

Highlights: [•] Er3+/Yb3+/Ce3+ tri-doped tellurite glasses containing WO3 were prepared. [•] The structure behavior and 1.53μm band luminescence properties were investigated. [•] Introduction of WO3 improves 1.53μm fluorescence due to enhanced energy transfer. [•] The ET mechanisms were investigated via calculating micro-parameters. [ABSTRACT FROM AUTHOR]

Abstract: Er3+ single doped and Er3+/Tm3+ co-doped tellurite glasses with composition of TeO2–ZnO–Na2O were prepared by the melt-quenching method, and the absorption and fluorescence spectra were measured. The intensity parameters (t =2, 4, 6), spontaneous radiative transition rates A, fluorescence branching ratios β and radiative lifetimes of Tm3+ ions were calculated from the measured absorption spectra based on the Judd–Ofelt theory, and the luminescence properties of samples with different doped concentration of Er3+–Tm3+ ions were investigated from the measured fluorescence emission spectra under the 800nm LD excitation. It was shown that the 1.53μm fluorescence emission intensity of Er3+ ions decreases with the increasing of Tm3+ ion doped concentration, while the 1.85μm fluorescence emission intensity of Tm3+ ions increases accordingly. The energy transfer mechanisms between Er3+ and Tm3+ ions were investigated to explain the fluorescence varying behavior, and it indicates that phonon-assisted non-resonant energy transfers from Er3+ to Tm3+ ions play a very important role in the 1.85μm fluorescence emission of Tm3+ ions. The energy transfer coefficient and phonon contribution for the existed energy transfer process between Er3+ and Tm3+ ions were calculated and analyzed. Meanwhile, the 1.85μm band stimulated absorption, emission cross-sections and gain coefficient of Tm3+:3F4 → 3H6 transitions were also obtained and analyzed. The research shows that Er3+/Tm3+ co-doped TeO2–ZnO–Na2O glass is a promising host material applied for 1.85μm band solid lasers and amplifiers. [Copyright &y& Elsevier]

• The high content (6.0 mol%) Er3+ ions doped ZrF 4 -BaF 2 -LaF 3 -AlF 3 -NaF (ZBLAN) fluoride glass sample with low OH- concentration (0.013 cm−1) was prepared. • The radiative trapping effect of Er3+ ions with different sample size has been investigated. • The numerical modeling results showed the mid-infrared output-laser improved greatly and even exceeded the Stokes limit. The influence of radiation trapping effect on the fluorescence and decay of the heavy concentration Er3+ doped ZBALN glass were investigated, and numerical simulation proves that high-slope efficiency 2.7 µm laser output can be achieved. ga1 The ZBLAN glass with high content of Er3+ was prepared and studied. The glass has a wide infrared transmittance range of 2.5–8.0 µm, which means a lower maximum phonon energy. By testing and analyzing the fluorescence spectrum and lifetime curves under different penetration depths, the intrinsic emission spectrum and lifetime of the sample are obtained without the influence of sub-absorption. Under 980 nm excitation, the maximum emission cross section and the lifetime of 2.7 µm are 6.10 × 10−21 cm2 and 6.49 ms, indicating that high-concentration doping has a larger laser quality factor. According to the rate equation and transmission equation, cascaded and non-cascaded fiber laser models are established to conduct research on 2.7 µm fiber lasers. The slope efficiency can reach 40.38% at a pump wavelength of 980 nm and a fiber background loss of 0.1 dB/m. The high emission cross section, long fluorescence lifetime and high slope efficiency output make ZBLAN glass heavily doped with Er3+ an ideal host material for mid-infrared lasers. [ABSTRACT FROM AUTHOR]