Analysis of mid-infrared photoluminescence around 2.85 μm in Yb3+/Ho3+ co-doped synthetic silica-germanate glass

2.85 μm fluorescence of Ho3+ was firstly obtained in Yb3+/Ho3+ co-doped silica-germanate glass. The combination of low OH− concentration and high mid-infrared transmittance were beneficial to the realization of mid-infrared emissions. A large calculated spontaneous radiative transition probability (30.27 s−1) corresponding to the Ho3+:5I6 → 5I7 transition was beneficial for high gain and more opportunity to achieve laser action. Besides, enhanced green (548 nm) and red (662 nm) emissions were obtained due to the energy transfer between Yb3+ and Ho3+. Moreover, the measured lifetime of Ho3+:5I6 reached as high as 283 μs in Yb3+/Ho3+ co-doped silica-germanate glass, which also possesses a large emission cross section (8.05 × 10−21 cm2). All results reveal that Yb3+/Ho3+ co-doped silica-germanate glass might provide a new choice for 2.85 μm laser applications.