•Telluride glasses with high Er3+ doping concentration and good thermal property are prepared.•Energy transfer processes for 1.5 μm, 2.7 μm and visible emission are fully discussed.•Enhanced 2.7 μm emission is achieved from the bulk glasses.•An Er3+ doped fiber is successfully drawn and strong upconversion emission is observed in the fiber.Emissions at 2.7 μm from telluride glasses with various Er2O3 doping concentrations are investigated. The prepared glasses have excellent thermostability and high rare-earth solubility. Judd–Ofelt parameters are calculated based on the absorption spectra. A large emission cross section (1.12 × 10−20 cm2) and a high spontaneous radiative coefficient (57.8 s−1) are obtained at 2.7 μm. The fluorescence properties of glasses with different concentrations are analyzed and presented. An Er3+-doped fiber is fabricated via a rod-in-tube technique, and the loss at 1310 nm is ∼2.1 dB/m measured by using the cut-back method. Strong upconversion emission caused by intense pump absorption is observed from the Er3+doped fiber under excitation by a 980 nm laser diode (LD).Telluride glasses with high Er3+ doping concentration and good thermal property are prepared. Energy transfer processes for 1.5 μm, and 2.7 μm, as well as visible emission are fully discussed. Enhanced 2.7 μm emission is achieved from the bulk glass. An Er3+ doped fiber is successfully drawn, and strong upconversion emission is observed in the fiber.

In this work, we report near infrared emission spectra of Er3+–Tm3+ co-doped Bi2O3–GeO2–Na2O (BGN) glasses with the excitation of 800 nm laser. A broad emission extending from 1300 to 1650 nm with a full width at half maximum (FWHM) of ∼160 nm is obtained in a 1.0 wt% Tm2O3 and 0.3 wt% Er2O3 co-doped BGN glass. The energy transfer processes between Tm3+ and Er3+ in BGN glasses are analyzed in detail. The temperature dependence of the broadband emission spectra in Er3+–Tm3+ co-doped BGN glass is also studied. The present work indicates that Er3+–Tm3+ co-doped BGN glasses can be promising materials for broadband light sources and broadband amplifiers for WDM transmission systems.Graphical abstractRoom temperature emission spectra of Er3+ singly doped and co-doped with Tm3+ BGN glasses with the excitation of 800 nm laser.Research highlights▶ Novel bismuthate glass Bi2O3–GeO2–Na2O (BGN) as Er3+–Tm3+ co-doping host. ▶ A broad emission extending from 1300–1650 nm with a full width at half maximum (FWHM) of ∼160 nm is obtained. ▶ The temperature dependence of the broadband emission spectra in Er3+–Tm3+ co-doped BGN glass is analyzed.

Tm3+-doped and Tm3+/Yb3+-codoped TeO2–ZnO–Bi2O3 (TZB) glasses are prepared by melt-quenching method. The Judd-Ofelt intensity parameters (Ωtt = 2, 4, 6), radiative transition rate, and radiative lifetime of Tm3+ are calculated based on the absorption spectra. The 1.8 μm emission of the samples is investigated under 980 nm laser excitation. The absorption, emission cross-sections, and gain coefficient of Tm3+:3F4 → 3H6 are calculated. The energy transfer processes of Yb3+–Yb3+ and Yb3+–Tm3+ are analyzed, the results show that the Yb3+ ions can transfer their energy to Tm3+ ions with large energy transfer coefficient, and a maximum efficiency of 79%.

Tm3+/Yb3+-codoped lanthanum tungsten tellurite (TWL) glasses are prepared by melt-quenching method and the thermal stability of the glasses is analyzed. To evaluate the spectroscopic properties of Tm3+ in TWL glass, the Judd–Ofelt intensity parameters (Ωtt = 2, 4, 6), radiative transition rates, radiative lifetimes, and branching ratios of Tm3+ are calculated based on the absorption spectrum. The 1.8 μm emission of the samples are investigated under the excitation of 980 nm LD. Large product of emission cross-section and lifetime (σemτR) of Tm3+: 3F4 → 3H6 is obtained, and the maximum gain coefficient at around 1835 nm is 3.6 cm−1. The energy transfer processes of Yb3+–Yb3+ and Yb3+–Tm3+ are analyzed, the results show that the Yb3+ ions can transfer their energy to Tm3+ ions with a large energy transfer coefficient, and a maximum efficiency of 89%.

Ho3+/Yb3+ codoped lanthanum–tungsten–tellurite (TWL) glasses are prepared by melt-quenching method. The Judd–Ofelt intensity parameters (Ωt t = 2, 4, 6), radiative transition rates, radiative lifetimes, and branching ratios of Ho3+ are calculated based on the absorption spectrum to evaluate the spectroscopic properties of Ho3+ in TWL glass. The mid-infrared emission of the samples are investigated under the excitation of 980 nm LD. The absorption, emission cross-sections and gain coefficient of Ho3+:5I7 → 5I8 are calculated. The energy transfer processes of Yb3+–Yb3+ and Yb3+–Ho3+ are analyzed, the results show that the Yb3+ ions can transfer their energy to Ho3+ ions with large energy transfer coefficient, and a maximum efficiency of 84%.

In this work, we report the infrared emission properties of Tm3+/Ho3+ co-doped TeO2–WO3–La2O3 (TWL) glass under 808 nm laser excitation. A broad and flat emission from 1600 to 2200 nm corresponding to the Tm3+ (3F4→3H6) and Ho3+ (5I7→5I8) emissions is observed. The full width at half maximum (FWHM) of this broadband increases up to a value of ∼370 nm with an optimal [Tm3+]/[Ho3+] concentration ratio. The energy transfer processes of Tm3+↔Ho3+ are analyzed and the results show that energy transfer between Tm3+ and Ho3+ plays an important role in the luminescence mechanism. The OH− influence on the broadband emission is also discussed. These results indicate that Tm3+–Ho3+ co-doped TWL glass could be a promising material for widely tunable laser or broadband amplifier applications.