Spectroscopic Properties of Ho³⁺/Tm³⁺/Yb³⁺ co-Doped SiO₂-Bi₂O₃-BaF₂-AlPO₄ Glass

Fiber laser in 2 μm spectral region can attach great importance, not only on health care, but also in laser radar, air monitoring and other fields such as environmental pollution. Due to its important application in the medical field, fiber laser in 2 μm spectral region opened the floodgates to new research. Compared to other glass matrixes, silicate glass has low cost, good chemical stability, but high phonon energy, high melting temperature, low rare earth ion solubility, difficult to realize miniaturization of equipment and other shortcomings. The introduction of bismuth oxide in silicate glass Bi₂O₃, can reduce the phonon energy, melting temperature and increase the solubility of rare earth ions. Meanwhile, the O-H in the glass hosts can be removed with increasing concentration of fluorine ions in the glass, and thus improve 2 μm infrared luminous performance. Therefore bismuth silicate glass is considered as an ideal near-mid-infrared light-emitting material. The bismuth silicate glass SiO₂-Bi₂O₃-BaF₂-AlPO₄ doped with Ho³⁺/Tm³⁺/Yb³⁺ is prepared by high-temperature melt-quenching method. Compared with physical properties, phonon energy and optical performance, 50SiO₂-40Bi₂O₃-5BaF₂-5AlPO₄ (SBBA) is the appropriate glass host. The spectroscopic properties of bismuth silicate exited by 980 nm laser diode were investigated. The Judd-Ofelt parameters and radiative lifetime of Ho³⁺ in SBBA doped with 0.5Ho₂O₃-2.0Yb₂O₃ (HY), 0.5Ho₂O₃-0.5Tm₂O₃-2.0Yb₂O₃ (0.5HTY), 0.75Ho₂O₃-0.75Tm₂O₃-3.0Yb₂O₃ (0.75HTY) respectively, were calculated based on the absorption spectra. The maximal absorption and emission cross sections (σ_em) of Ho³⁺ are 7.38×10^-21, 10.54×10^-21 cm², respectively, while the largest FWHM×σ_em achieves 19.71×10^-26 cm³ in SBBA-0.75HTY. The results of fluorescence spectra suggest more efficient application in 2 μm fiber lasers of Ho³⁺, Tm³⁺ and Yb³⁺ co-doped bismuth silicate than Ho³⁺ and Yb³⁺ co-doped bismuth silicate. SiO₂-Bi₂O₃-BaF₂-AlPO₄ doped with Ho³⁺/Tm³⁺/Yb³⁺ can attach better infrared light-emitting performance and gain effect with high doping concentration in a fixed ratio of rare earth ions.