Enhanced 2-5 μm emission in Ho³⁺/Yb³⁺ codoped halide modified transparent tellurite glasses.

Ho(3+)/Yb(3+) codoped TeO₂-WO₃-ZnO-ZnX₂(X=F, Cl) glasses were prepared by melt-quenching method. The absorption spectra, transmittance spectra, X-ray diffraction (XRD) curves, Raman spectra and mid-infrared fluorescence spectra were measured, along with the Judd-Ofelt intensity parameters, stimulated emission and absorption cross-sections were calculated to evaluate the effects of halide amount of the spectroscopic properties. It is shown that the introduction of an appropriate amount of halide can further improve the mid-infrared fluorescence intensity through an enhanced phonon-assisted energy transfer between Ho(3+)/Yb(3+) ions and the energy transfer mechanisms are investigated quantitatively in detail by calculating energy transfer microparameters and phonon contribution ratios. The results indicate that this kind of glasses is a promising material for mid-infrared optical fiber.