Insight into the role of Er3+ local structure in thermal stability enhancement and concentration quenching suppression for germanate glasses

Er 3+ -doped oxide glasses face severe concentration quenching at high doping levels, limiting their emission efficiency and laser performance. Here, a germanate glass system achieves ultrahigh Er 3+ doping concentration (11.91 × 10 20 cm −3 ) without significant quenching while enhancing thermal stability (ΔT = 242 °C). Under 980 nm excitation, the 2.7 μm emission exhibits nearly linear intensity growth (R 2 = 97.4%) and achieves a high gain coefficient of 5.75 cm −1 . Moreover, the up-conversion emission shows a tunable color from yellow-green to orange-red, achieving a maximum absolute temperature sensitivity of 3.352 × 10 −3 K −1 at 558 K. The local structure evolution of the Er 3+ and glass network was systematically investigated using Raman spectroscopy, Pair distribution function (PDF), and X-ray absorption fine structure (XAFS). This local structural engineering strategy not only provides a viable route for developing high-performance Er 3+ -doped germanate glasses but also broadens prospects for applications in high-power 2.7 μm fiber lasers and multifunctional optical sensors.