•Nd3 + doped tellurite glass with and without WO3 oxide was prepared using melt-quenching method.•Three 0.9, 1.06 and 1.34 μm emissions increase greatly with the addition of WO3 oxide.•The great increase of near-infrared emission is mainly attributed to the enhanced MPR.•Nd3 + doped tellurite glass with WO3 oxide is promising for near-infrared lasers and amplifiers.Tellurite glasses with different concentrations of Nd3 + ions and WO3 oxide were prepared using melt-quenching technique. The prepared glasses were characterized by the absorption spectrum, emission spectrum, Raman spectrum, fluorescence decay curve and DSC curve measurements, together with Judd-Ofelt intensity parameter, radiative transition probability and fluorescence branching ratio calculations to reveal the effects of Nd3 + and WO3 concentration on the structure, photo-luminescence and thermal stability. Under the excitation of 808 nm LD, three near-infrared band fluorescence emissions at around 0.9, 1.06 and 1.34 μm, corresponding to the transitions from the 4F3/2 → 4I9/2, 4I11/2 and 4I13/2 levels respectively, are observed, and the fluorescence intensities increase with the increase of doped Nd3 + concentration up to 0.6 mol%. Furthermore, the fluorescence intensities continue to increase greatly with the introduction of WO3 oxide. Compared with 0.6 mol% Nd3 +-doped glass without WO3 oxide, the luminescent intensity of 1.06 μm band increases by about 95% in the glass with 9 mol% amount of WO3, which is mainly attributed to the rapid population of Nd3 + ions in the excited level 4F3/2 due to the enhanced multi-phonon relaxation process with the increased phonon energy of glass host. Therefore, the enhanced luminescent intensity as well as the good thermal stability demonstrated by DSC curve indicate that the prepared 0.6 mol% Nd3 +-doped tellurite glass with 9 mol% amount of WO3 oxide is a potential gain medium applied for near-infrared band solid-state lasers and fiber amplifiers.

•Pr3+-doped tellurite glass with Ag NPs was prepared using melt-quenching technique.•The spectroscopic property was analyzed by the modified Judd-Ofelt theory.•The ultra-broadband emission (1250–1650 nm) of Pr3+ was obtained under 488 nm pump.•The ultra-broadband fluorescence increased greatly with the introduction of Ag NPs.•The fluorescence enhancement is mainly due to the increased LEF induced by Ag NPs.Pr3+-doped tellurite glasses containing metallic silver NPs were synthesized by the conventional melt-quenching technique. Structural, thermal and optical properties of the synthesized glass samples were characterized by X-Ray diffraction (XRD) curves, Raman spectra, differential scanning calorimeter (DSC) curves, transmission electron microscopy (TEM) images, UV/Vis/NIR absorption and near-infrared fluorescence emission spectra. The XRD curves confirmed the amorphous structural nature of the synthesized glasses, the Raman spectra identified the presence of different vibrational groups, the DSC curves verified the good thermal stability, and the TEM images revealed the nucleated silver NPs with average diameter about 10 nm dispersed in the glass matrix and its surface Plasmon resonance (SPR) absorption band was located at around 510 nm. Besides, Judd-Ofelt intensity parameters Ωt(t = 2, 4, 6) and other important spectroscopic parameters like transition probability, radiative lifetime, branching ratio were calculated to evaluate the radiative properties of Pr3+ levels from the measured optical absorption spectra. It was found that Pr3+-doped tellurite glasses could emit an ultra-broadband fluorescence extending from 1250 to 1650 nm under the 488 nm excitation, and this fluorescence emission increased further with the introduction of silver NPs. The enhanced fluorescence was mainly attributed to the increased local electric field around Pr3+ induced by silver NPs. The present results demonstrate that Pr3+-Ag codoped tellurite glass is a promising candidate for the near-infrared band ultra-broadband fiber amplifiers covering the expanded low-loss communication window.

•Ag NPs was embedded into Er3+/Tm3+/Yb3+ doped tellurite glass prepared by melt-quenching method.•The 1.81 μm band fluorescence of Tm3+ increased greatly with the embedding of Ag NPs.•The increased fluorescence is mainly attributed to the enhanced local field induced by Ag NPs.•The enhanced field promotes the radiative transition demonstrated by fluorescence dynamics.•The ET mechanism including micro-parameters between Er3+ and Tm3+ were presented.Metallic silver nanoparticles (Ag NPs) with various concentrations were embedded into Er3+/Tm3+/Yb3+ tri-doped tellurite glasses prepared using melt-quenching and heat-treated techniques. Heat-treatment at temperature above the glass transition temperature induced the nucleation and growth of near-spherical shape silver NPs confirmed by the transmission electron microscopy (TEM) images, and the average diameter of silver NPs was about 10 nm. The thermal stability, structural and optical properties of the prepared glasses were characterized by the differential scanning calorimeter (DSC) curves, X-ray diffraction (XRD) patterns, absorption spectra, luminescence spectra and fluorescence decay curves. The DSC curves displayed that the prepared glasses possess good thermal stability with ∆T larger than 138 °C while the XRD patterns indicated the amorphous structural nature. Under the excitation of 980 nm LD, the luminescence spectra exhibited two intense near-infrared band fluorescence at 1.81 and 1.53 μm in the wavelength range of 1400–2200 nm, which are originated from the Tm3+:3F4 → 3H6 and Er3+:4I13/2 → 4I15/2 transitions respectively. With the embedding of 0.5 mol % amount of silver NPs, the 1.81 μm band fluorescence of Tm3+ increased significantly by about 70%, mainly due to the local electric field enhanced effect induced by silver NPs on the basis of energy transfers from Er3+ to Tm3+ ions, and the energy transfer efficiency, micro-coefficient and critical radius were calculated to elucidate the interaction mechanism between Er3+ and Tm3+ ions. Additionally, the intensity parameters Ωt(t = 2, 4, 6) and radiative properties of Tm3+ such as the transition probabilities, radiative lifetimes and branching ratios were calculated from the measured absorption spectra based on Judd-Ofelt theory. The present results indicate that the Er3+/Tm3+/Yb3+ tri-doped tellurite glass with an appropriate amount of silver NPs is a promising luminescent material applied for the near-infrared band solid-state lasers and fiber amplifiers.

•Er3+/Yb3+ codoped tellurite glass with Ag NPs was prepared by melt-quenching method.•Ag NPs with mean diameter of ∼11.4 nm was synthesized in glass heat-treated for 24 h at 370 °C.•The synthesized Ag NPs greatly enhanced 1.53 μm band fluorescence intensity of Er3+.•The fluorescence improvement was mainly attributed to the enhanced local field induced by Ag NPs.•The enhanced field was demonstrated by comparing the emission spectra of hypersensitive probe Eu3+.Improving the spectroscopic properties of rare earth (RE) doped glass materials is a challenging task. In the present work the metallic silver nanoparticles (Ag NPs) were embedded into Er3+/Yb3+ codoped tellurite glasses with composition TeO2–Bi2O3–TiO2, prepared using melt-quenching and subsequent heat-treated techniques, and the improved effect of Ag NPs on the 1.53 μm band fluorescence of Er3+ ions was investigated. About 24 h heat-treatment of Er3+/Yb3+ codoped tellurite glass containing 1 mol % amount of AgNO3 at the temperature 370 °C yielded the well-dispersed and near-spherical Ag NPs with ∼11.4 nm average diameter as evidenced by transmission electron microscopy (TEM) image. The intense 1.53 μm band fluorescence was observed in the prepared Er3+/Yb3+ codoped tellurite glasses under the excitation of 980 nm and was further improved with the presence of Ag NPs in the glass matrix, which is attributed to the enhanced local electric field around doped RE ions induced by Ag NPs and the possible energy transfer from Ag NPs to Er3+ ions. The enhanced local electric field was well demonstrated by comparing the variation of emission spectra of hypersensitive probe Eu3+ ions in tellurite glasses with and without Ag NPs. From the Judd-Ofelt analysis, it was also found that the value of Ω6Ω6 intensity parameter increased slightly with the increase of Ag NPs concentration in a certain range, also confirming the possibility of realizing strong fluorescence emission. In addition, the amorphous structural nature was demonstrated by the measured X-ray diffraction (XRD) patterns with no sharp diffraction peak. The enhanced 1.53 μm band fluorescence indicates that the Er3+/Yb3+ codoped tellurite glass with an appropriate amount of Ag NPs is a promising candidate for the development of Er3+-doped fiber amplifiers (EDFAs) applied in the WDM systems.

•Er3+/Nd3+ codoped tellurite glass was prepared by conventional melt-quenching method.•The prepared tellurite glass exhibited good thermal stability with ΔT > 170 °C.•The 2.7 μm fluorescence enhanced greatly owing to the energy transfers from Nd3+.•Quantitative study of energy transfer mechanism and phonon contribution was presented.Nd3+ was introduced into Er3+ doped tellurite glass with composition of TeO2Nb2O5ZnONa2O 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 Nd3+ introduction on the spectroscopic properties especially the 2.7 μm band fluorescence of Er3+. 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 Nd3+ significantly improves the 2.7 μm band fluorescence intensity through joint energy transfer processes between the relevant excited levels of Er3+ and Nd3+, 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 Er3+/Nd3+ codoped tellurite glass is a potential glass medium applied for the 2.7 μm mid-infrared band lasers.

•Yb3+/Nd3+/Tm3+ tri-doped tellurite glass was prepared using melt-quenching technique.•The prepared glass has improved thermal stability with ΔTΔT larger than 186 °C.•The tri-doped glass exhibits intense blue upconversion under the 980 nm excitation.•The prepared tri-doped glass reveals potential applications in blue fiber lasers.New Yb3+/Nd3+/Tm3+ tri-doped tellurite glasses (TeO2–Bi2O3–ZnO–Na2O) with improved thermal stability and intense blue upconversion emission were prepared by melt-quenching technique. The thermal stability and blue upconversion of glass samples were investigated by means of differential scanning calorimeter (DSC) and fluorescent spectrophotometer measurements. DSC results show that the prepared tellurite glasses have favorable thermal stability for fiber drawing and the difference (ΔT)(ΔT) between the estimated crystallization onset temperature (Tx)(Tx) and the transition temperature (Tg)(Tg) reaches about 186 °C, which is larger than that of some other tellurite glass hosts. Under the excitation of 980 nm laser diode (LD), the tri-doped glass samples exhibit an intense blue (~474, 485 nm) upconversion emission, which is attributed to the simultaneous contributions from Tm3+:1G4→3H6 and Nd3+:2G9/2→4I9/2 transitions, and the possible upconversion luminescent mechanism based on the energy transfers from Yb3+ is presented. The above results indicate that the new synthesized Yb3+/Nd3+/Tm3+ tri-doped tellurite glass is a promising candidate applied for the blue solid-state lasers.

•Ho3+/Tm3+ codoped WO3 modified tellurite glass was prepared using melt-quenching technique.•The prepared glass exhibits an obvious enhancement of 2 µm fluorescence with the addition of WO3.•The prepared glass exhibits an improved thermal stability (ΔTΔT>140 °C) with the addition of WO3.•The Ho3+/Tm3+ codoped WO3 modified tellurite reveals potential applications in 2 µm band laser.A certain amount of WO3 oxide was introduced into the Ho3+/Tm3+ codoped tellurite glass, and the absorption spectra, fluorescence spectra, Raman spectra, X-ray diffraction patterns and differential scanning calorimeter curves were measured to illustrate the enhanced effects of WO3 on the 2 µm fluorescence of Ho3+ and thermal stability of glass host. Under the excitation of 808 nm LD, the 2 µm fluorescence of Ho3+ increases obviously with the partial substitution of TeO2 by WO3 oxide, which is attributed to the enhanced energy transfer process from Tm3+:3F4 to Ho3+:5I7 level by providing a relatively large phonon energy. Meanwhile, the thermal stability of glass host increases accordingly, which is mainly attributed to the formation of thermal stability W=O bond. The intense 2 µm fluorescence together with good thermal stability indicates that Ho3+/Tm3+ codoped WO3 modified tellurite glass is a potential laser glass for efficient 2 µm emission.

•New Ho3+/Yb3+ codoped tellurite glass was prepared using melt-quenching method.•The thermal stability of glass sample increased with rare-earth doped concentration.•Codoping with Yb3+ led to intensive green and red upconversion of Ho3+ owing to ET.•ET mechanism was investigated by calculating micro-coefficient and phonon contribution.•The prepared Ho3+/Yb3+ codoped tellurite glass is suitable for visible-band fiber laser.New Ho3+/Yb3+ codoped tellurite glasses (TeO2–Bi2O3–ZnO–Na2O) prepared by melt-quenching technique were investigated to realize visible-band upconversion emissions applied for compact fiber lasers. The absorption spectra, upconversion emission spectra, differential scanning calorimetry (DSC) curves, X-ray diffraction (XRD) and Raman spectra were measured to characterize the spectroscopic properties of Ho3+, thermal stability and structural nature of glass hosts. Under the excitation of 980 nm laser diode (LD), the intense green (∼543 nm) and red (∼657 nm) upconversion emissions corresponding to 5F4(5S2) → 5I8 and 5F5 → 5I8 transitions of Ho3+ respectively are simultaneously observed. The power dependence study of upconversion intensities on excited pump power revealed that the Ho3+ population at 5F4(5S2) and 5F5 levels was originated from two-photon absorption process based on the energy transfer from Yb3+ to Ho3+. The energy transfer mechanism from Yb3+ to Ho3+ was investigated and relevant micro-parameters (energy transfer coefficient and critical radius) and phonon contribution ratio were presented. With the increase of Yb3+ doped concentration, both the green and red upconversion intensities enhanced greatly, meanwhile the thermal stability of glass hosts, characterized by the three characteristic temperatures, also got a slight improvement. Furthermore, the glass structure was briefly analyzed with the calculated Judd–Ofelt intensity parameters, the measured Raman spectra and XRD curves. The present results indicate that the new synthesized Ho3+/Yb3+ codoped tellurite glass with intense green and red upconversion emissions is a promising medium applied for the visible-band fiber lasers.

•Er3+/Ce3+ co-doped tellurite glass with B2O3 was prepared using melt-quenching method.•The large phonon energy induced by B2O3 promoted energy transfer from Er3+ to Ce3+.•1.53 μm fluorescence of Er3+ increased greatly with an enhanced phonon-assisted ET.•ET mechanisms were investigated quantitatively via calculating microscopic parameters.•1.53 μm band signal gain of Er3+/Ce3+ codoped tellurite glass fiber improved with B2O3.Er3+/Ce3+ co-doped and B2O3 modified tellurite glasses with initial composition of TeO2–GeO2–Li2O–Nb2O5 were prepared using melt-quenching technique for potential applications in Er3+-doped fiber amplifiers (EDFAs) and lasers. The absorption spectra, fluorescence spectra, up-conversion spectra, Raman spectra and differential scanning calorimeter (DSC) curves of glass samples were measured to evaluate the effect of B2O3 modification on the 1.53 μm band spectroscopic properties of Er3+, structural nature and thermal stability of glass hosts. It was shown that the introduction of an appropriate amount of B2O3 oxide can further improve the 1.53 μm band fluorescence emission through an enhanced phonon-assisted energy transfer (ET) from Er3+ to Ce3+ ions under the excitation of 980 nm, and the quantitative studies were carried out to elucidate the ET mechanism via calculating the microscopic parameters and phonon contribution ratios. Meanwhile, the thermal stability of glass hosts increases slightly with the introduction of B2O3 oxide. Furthermore, the 1.53 μm band optical signal amplification was simulated based on the rare-earth ion rate and light power propagation equations. An increment in signal gain by about 1.4 dB at 1532 nm was observed in the Er3+/Ce3+ co-doped tellurite glass fiber containing 6 mol% amount of B2O3 oxide, and the maximum signal gain reaches to 31 dB on a 50 cm fiber pumped at 980 nm with power 200 mW. The present results indicate that the prepared Er3+/Ce3+ co-doped tellurite glass modified by an appropriate amount of B2O3 oxide has good prospect as a gain medium applied for 1.53 μm band EDFAs and lasers.

•Er3+/Ce3+ codoped tellurite glass with Ag NPs was prepared by melt-quenching method.•Near-spherical Ag NPs with average diameter of ∼19 nm was synthesized in glass.•The introduced Ag NPs greatly enhanced 1.53 μm fluorescence intensity of Er3+.•Intense fluorescence is attributed to enhanced local field and ET from Er3+ to Ce3+.•The thermal stability of tellurite glass increased with the introduction of Ag NPs.The silver nanoparticles (Ag NPs) was introduced into Er3+/Ce3+ codoped tellurite glasses with composition of TeO2–ZnO–La2O3 and the effects of Ag NPs on the 1.53 μm band spectroscopic properties of Er3+ ions, structural nature and thermal stability of glass hosts were investigated. The absorption spectra, upconversion emission spectra, 1.53 μm band fluorescence spectra together with the X-ray diffraction (XRD) patterns, differential scanning calorimeter (DSC) curves and transmission electron microscopy (TEM) image were measured. It was found that the near-spherical shape Ag NPs with average diameter of about 19 nm dispersed uniformly in the glass matrix, and the Er3+/Ce3+ codoped tellurite glasses containing Ag NPs exhibited an obvious enhancement in the 1.53 μm band fluorescence, which is attributed to the intensified local electric field induced by Ag NPs and the possible energy transfer from Ag NPs to Er3+ ions. The enhanced effect of Ag NPs on the 1.53 μm band fluorescence was elucidated by the obtained large Judd–Ofelt intensity parameter Ω6 and the calculated quantum efficiency of Er3+:4I13/2 level. In addition, the thermal stability of prepared glass samples increased with the introduction of Ag NPs and the amorphous structural nature was demonstrated by the measured XRD patterns with no sharp diffraction peak. The present results indicate that the prepared Er3+/Ce3+ codoped tellurite glass with Ag NPs has good prospect as a gain medium applied for 1.53 μm band Er3+-doped fiber amplifiers (EDFAs).

•Er3+/Ce3+/Yb3+ co-doped tellurite glasses were prepared using melt-quenching method.•The prepared RE doped tellurite glasses exhibited good thermal stability with ΔTΔT>145 °C.•The 1.53 µm fluorescence of Er3+ increased greatly with the addition of Ce3+ and Yb3+.•The ET mechanisms between Yb3+/Er3+ and Er3+/Ce3+ were investigated quantitatively.Tellurite glasses (TeO2–ZnO–La2O3) doped with Er3+, Er3+/Ce3+ and Er3+/Ce3+/Yb3+ have been prepared using the melt-quenching technique, and the absorption spectra, fluorescence and up-conversion emission spectra together with the differential scanning calorimeter (DSC) curves and X-ray diffraction (XRD) patterns were measured to evaluate the effects of Ce3+ and Yb3+ introduction on the 1.53 µm band spectroscopic properties of Er3+, thermal stability and structural nature of glass hosts. The Judd–Ofelt intensity parameters ΩtΩt (t=2,4,6), spontaneous emission probabilities, radiative lifetimes and branching ratios of several Er3+ transitions were calculated from the measured absorption spectra based on the Judd–Ofelt theory. The co-doping with Ce3+ was effective on the suppression of up-conversion emission of Er3+ owing to the phonon-assisted energy transfer: Er3+:4I11/2+Ce3+:2F5/2→Er3+:4I13/2+Ce3+:2F7/2, while the co-doping with Yb3+ had the effect of obviously increasing the Er3+ population at 4I11/2 level via the resonant energy transfer: Yb3+:2F5/2+Er3+:4I15/2→Yb3+:2F7/2+Er3+:4I11/2, both of which contributed the effective enhancement of 1.53 µm fluorescence emission. The quantitative studies were carried out to elucidate the energy transfer mechanism by calculating the microscopic parameters and phonon contribution ratios. The glass transition temperature (TgTg), crystallization onset temperature (TxTx) and the difference ΔT(=Tx−Tg)ΔT(=Tx−Tg), which characterize the thermal stability of glass host, increased with the Ce3+ and Yb3+ co-doping and for all glass samples the value of ΔTΔT is larger than 145 °C. The glass structural nature was demonstrated from the measured XRD patterns with no sharp diffraction peaks. The results of the present work indicated that the prepared Er3+/Ce3+/Yb3+ co-doped tellurite glass is a potential material for developing broad-band and high-gain optical amplifiers and other optical devices.

•Ho3 +/Yb3 + co-doped tellurite glass containing silver NPs was prepared.•Introduction of silver NPs significantly enhanced upconversion emission of Ho3 +.•Addition of silver NPs increased the thermal stability of the prepared glass.•The ET mechanism from Yb3 +:2F5/2 to Ho3 +:5I6 level was investigated quantitatively.Ho3 +/Yb3 + codoped zinc-tellurite glasses containing silver nanoparticles (NPs) were prepared using the conventional melt-quenching technique. The detailed effect of silver NPs on the upconversion emission of Ho3 +, thermal stability and structure behavior of glass hosts was investigated from the measured absorption spectra, upconversion emission spectra, differential scanning calorimeter (DSC) curves, X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM) images. Two frequency upconversion emission bands centered at 546 nm (green) and 657 nm (red) corresponding to Ho3 + transitions of 5F4(5S2) → 5I8 and 5F5 → 5I8, respectively, are simultaneously observed under the 980 nm excitation at room temperature. It is shown that the introduction of silver NPs can further improve the upconversion emissions of Ho3 +and thermal stability of glass host, while the glass structure maintains the amorphous nature. The enhanced upconversion emission is mainly attributed to the increased local electric field around Ho3 +induced by localized surface plasmon resonance (LSPR) effect of silver NPs. Furthermore, the energy transfer (ET) mechanism from Yb3 +:2F5/2 level to Ho3 +:5I6 level is quantitatively analyzed by calculating relevant micro- parameters and phonon contribution ratio.

A series of Er3+-doped Bi2O3–B2O3–GeO2–Na2O glasses with different OH− group contents were prepared and the interactions between Er3+ ions and OH− groups were investigated. The observed increase of the fluorescence intensity and decaying variation from an evident non-exponential to a nearly exponential behavior of the Er3+:4I13/2 level with the oxygen gas bubbling time was related to the reduction of the OH− group contents evidenced by infrared (IR) absorption spectra, which demonstrated that the OH− groups were dominant quenching centers of the excited Er3+. Meanwhile, by reducing the OH− group contents in the fiber cores with the same glass composition, the simulated gain characteristics improved dramatically and a 12.4 dB gain at 1560 nm was achieved in a 20 cm fiber with 150 mW pumping power at 980 nm.

The B2O3 component was introduced into Er3+/Ce3+ co-doped TeO2–ZnO–Na2O–Nb2O5 glass to improve energy transfer rate of Er3+:4I11/2→Ce3+:2F5/2 phonon-assisted cross-relaxation process. With the 6 mol% substitution of B2O3 for TeO2, the energy transfer rate increased from 1300 to 1831 s−1 and the fluorescence intensity increased by about 13.4%. However, the more B2O3 substitution in the same glass system reduced the quantum efficiency of Er3+:4I13/2→4I15/2 transition due to the higher OH− group concentration. The results show that an appropriate amount of B2O3 component can be used to improve the phonon-assisted energy transfer rate and enhance 1.53 μm fluorescence emission by increasing the phonon energy of host glass. The effect of B2O3 on the energy transfer process, the lifetimes of the 4I11/2 and 4I13/2 levels, and the upconversion emission have also been investigated.

Spectroscopic properties of Er3+:4I13/2 → 4I15/2 transitions in erbium-doped bismuth-borate glasses with composition of 45Bi2O3–35B2O3–10GeO2–10Na2O were investigated. The results show that the fluorescence intensity reveals a nonexponential decaying behavior for glasses with low Er3+-doped concentration. It is ascribed to the energy transfer from Er3+ to OH− groups, and the energy-transfer microparameter CEr–OH is about 33.1 × 10−40 cm6 s−1 in Er2O3-doped content of 0.1 mol% glass. Whereas an exponential behavior is dominant for glasses with high Er3+-doped case. Nonradiative decay in the latter is mainly originated from the energy migration among Er3+ ions, and this energy migration is also responsible for the concentration quenching of 1.53 μm fluorescence emission. The interaction microparameter CEr–Er for the migration among Er3+ ions was calculated to be an average of 43.9 × 10−40 cm6 s−1. Meanwhile, the radiation trapping of Er3+ leads to the effective emission width broadening from 66.3 to 82.5 nm with Er2O3 doped content increased from 0.1 to 3.0 mol%.

The comparative investigation on the spectroscopic properties of Er3+ in low phonon energy Bi2O3–GeO2–Ga2O3–Na2O glasses codoped with Ce3+ ion and added with B2O3 component, respectively, is presented. With increasing Ce2O3 content from 0 to 0.8 mol% or B2O3 content from 0 to 15 mol%, the lifetime of Er3+:4I11/2 level decreases dramatically from 607 to 283 μs or to 197 μs, and the upconversion fluorescence is quenched in both glass samples. The nonradiative energy transfer from Er3+:4I11/2→Ce3+:2F5/2 or the enhanced multiphonon relaxation process together with the energy transfer between Er3+ and OH− groups are, respectively, responsible for the results. Meanwhile, the lifetime of 4I13/2 level remains almost unchanged in Er3+/Ce3+-codoped glasses whereas it decreases rapidly in B2O3-added cases. As a result, Er3+/Ce3+ codoping improves the 1.5 μm fluorescence emission intensity, however, B2O3 addition has a negative effect on it. The research results indicate that the Er3+/Ce3+-codoped bismuth glasses will be preferable for obtaining efficient 980 nm pumped EDFA.

In order to improve the transition rate from the 4I11/2 level to the 1.53 μm fluorescence emitting 4I13/2 level of Er3+, the Ce3+ and Eu3+ ions were respectively introduced into the Er3+ doped bismuth-germanate glass with a composition of Bi2O3–GeO2–Ga2O3–Na2O. The energy transfer mechanisms between Er3+ and the codopants were discussed based on their energy level diagrams. Though Ce3+ was less effective than Eu3+ on the decrease of the 4I11/2 level lifetime, it hardly influenced the lifetime value of 4I13/2 level. Both the 4I11/2 and 4I13/2 levels were depleted severely at the same time with the codoping of Eu3+. As a result, Er3+/Ce3+ codoping improved the 1.53 μm fluorescence emission intensity, while Er3+/Eu3+ codoping had a deleterious effect on it. The results indicate that the Er3+/Ce3+ is a preferable codoped scheme for bismuth-germanate glass with low phonon energy to obtain an efficient broadband EDFA pumped at 980 nm.