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Rare-earth ions doped fiber lasers at 2 µm can supply various applications in daily life. In this paper, Ho3+/Yb3+ co-doped tellurite glasses were prepared by the high temperature melting method to obtain a strong 2 µm mid-infrared fluorescence emission. The characterization results of the X-ray diffraction (XRD) and differential scanning calorimeter (DSC) show that this glass possesses good crystallization resistance and thermal stability, and its ΔT is 136 °C, which can be successfully drawn. Under the 980 nm LD excitation, strong green (550 nm) and red (660 nm) up-conversion emission were obtained, meanwhile, intensive 2 µm mid-infrared emission was also achieved, and the emission intensity was significantly improved with the increase of Yb3+ concentration, when the Yb3+ content was 2.0, the 2 µm mid-infrared emission intensity was increased by about 28% compared with the content of 0.5, it should be noted that the concentration of Yb3+ is required to be strictly controlled to prevent concentration quenching. In addition, the luminescence process of Ho3+ was further elaborated through the energy transfer mechanism. All results indicate that the Ho3+/Yb3+ co-doped tellurite glass can be an attractive candidate for up-conversion and mid-infrared fiber laser materials. [ABSTRACT FROM AUTHOR]

Oxyfluoride silicate glasses co-doped with Cr3+ and Yb3+ ions were fabricated in this work. High △T (178–214 °C) value demonstrated that the thermal stability of the prepared glasses were better than tellurite and germanate glasses. X-ray diffraction (XRD) curves proved the amorphous nature of the glasses, the energy dispersive spectroscopy (EDS) analysis and Fourier Transform infrared spectroscopy (FT-IR) curves explored the network structure of glasses. The photoluminescence excitation (PLE) and photoluminescence emission (PL) spectra show that the glasses absorption peaks located at 430 nm (Cr3+:4A 2g - 4T 1g (P)) and 627 nm (Cr3+:4A 2g - 4T 2g), while the emission peak close to 1010 nm (Yb3+:2F 5/2 -2F 7/2), which meets the condition of energy down-conversion. Besides, the energy transfer efficiency (η CET = 33.5%) and the quantum cutting efficiency (η QE = 133.5%) were calculated from the measured decay curves. These values were higher than Cr3+/Yb3+ co-doped fluorosilicate glass with incorporating of CaF 2 (21.5% and 123.5%) and Tb3+/Yb3+ oxyfluoride glass (13.5% and 113.5%), indicating the prepared samples are conducive to the energy transfer from Cr3+ to Yb3+ ions. The experimental results reveal that the oxyfluoride silicate glasses have potential application prospects in crystalline silicon (c-Si) solar cells. [ABSTRACT FROM AUTHOR]

Fluorotellurite glasses tri-doped with Tm3+, Er3+ and Bi ions were investigated. The measured parameter ΔT (116 °C) confirmed that the prepared glasses had good stability. An ultra-broadband fluorescence emission (950–1670 nm) was observed with a full-width at half-maximum (FWHM) of 560 nm, which covered the entire bands of O, E, S, C, L and U. The 1800 nm fluorescence intensity of Tm3+/Er3+ co-doped and Tm3+/Er3+/Bi tri-doped glasses was enhanced compared to Tm3+ doped glass, which indicates that there is energy transfer between Tm3+, Er3+ and Bi ions. The maximum fluorescence lifetime of the prepared glasses was 7.39 ms, indicating the excellent fluorescence performance at 1800 nm. Additionally, the maximum absorption cross section (σ abs = 1.77 × 10−20 cm−2) and emission cross section (σ em = 7.61 × 10−20 cm−2) suggest that the Tm3+/Er3+/Bi tri-doped glasses have good optical absorption properties and high gain fluorescence emission. The above results indicate that the Tm3+/Er3+/Bi tri-doped fluorotellurite glasses have good application prospects in the field of fiber amplifiers and near-infrared lasers. [ABSTRACT FROM AUTHOR]