Abstract: Blue laser has a wide range of application prospects in the fields of color laser display, high-density optical storage, exploration of marine resource, underwater communication and biomedical sciences, etc. However, the relatively mature Yb³⁺ doped fiber laser can only obtain blue green (~490 nm) laser after frequency doubling. Therefore, it is an urgent issue to obtain a pure blue laser close to 450 nm. The 0.9 μm fluorescence generated by the ⁴F_3/2→⁴I_9/2 level transition of Nd³⁺ can obtain the pure blue laser output of ~450 nm after frequency doubling, which has excellent application potential in the field of blue laser. However, the fluorescence generated by this transition occupies a low fluorescence branching raito. In this paper, the absorption spectrum, fluorescence spectrum and fluorescence lifetime of 1% (mass fraction) Nd₂O₃ doped 50GeO₂-(20-x)PbO-15BaO-15ZnO-xNb₂O₅ (x%=0%, 2.5%, 5%, 10%, 15%,mole fraction) glass were systematically studied, and the corresponding Judd-Ofelt intensity parameters and gain bandwidth were calculated. It is found that the 900 nm absorption cross section, emission cross section, effective linewidth and fluorescence branching ratio of Nd³⁺ increase with the doping of Nb₂O₅. When the concentration of Nb₂O₅ is 10% (mole fraction), Judd-Ofelt intensity parameter Ω₂=5.91×10^-20 cm², the spectral quality parameter χ=1.01, and the fluorescence branching ratio is 42.9%. In summary, 0.9 μm fluorescence branching ratio of Nd³⁺ can be raised by Nb₂O₅, so as to obtain pure blue light (450 nm) by frequency doubling, which is beneficial to the development and application of blue laser.

Key words: Nd³⁺, Nb₂O₅ concentration, germanate glass, spectral property, Judd-Ofelt intensity parameter, ~0.9 μm fluorescence