Broadband mid-infrared 2.0 μm and 4.1 μm emission in Ho3+/Yb3+ co-doped tellurite-germanate glasses

Ho3+/Yb3+ co-doped tellurite-germanate glasses with lower phonon energy (779 cm−1) and higher thermal stability were prepared by conventional melt quenching. The mid-infrared fluorescence spectra of the prepared glasses were investigated by 980 nm laser pumping. The full width at half maximum (FWHM) and lifetime of the sample at 2.0 μm were 186 nm and 8.09 ms, respectively. Compared with the reported glasses for this type, these values were effectively improved. In particular, the FWHM and emission lifetime of the prepared glass at 4.1 μm reached 276 nm and 8.17 ms, respectively, which have not been reported yet. Meanwhile, compared to the recently reported tellurite glasses, the ΔT was increased by approximate 22.7%. Strong up-conversion visible emission peaks at 547, 662, and 756 nm and near-infrared emission at 1.20 μm were observed in Ho3+/Yb3+ co-doped glass. Meanwhile, photoluminescence measurements showed that the doping of the appropriate amount of Yb3+ ions significantly enhanced the emission intensity of the samples at 2.0 μm and 4.1 μm. Therefore, the Ho3+/Yb3+ co-doped tellurite-germanate glass is a promising candidate for mid-infrared fiber and laser materials applications. •Ho3+/Yb3+ co-doped tellurite-tellurite glass has a lower phonon energy (779 cm−1).•Ho3+/Yb3+ co-doped tellurite-tellurite glass has a larger ΔT (200 °C).•The full width at half maximum (FWHM) of the sample at 4.1 μm reached 276 nm.•The emission lifetime of the prepared glass at 4.1 μm reached 8.17 ms•The FWHM and lifetime of the sample at 2.0 μm were 186 nm and 8.09 ms, respectively.