Spectral properties of ultra-low thermal expansion Er3+/Yb3+co-doped phosphate glasses

An Er3+/Yb3+ co-doped phosphate glass with an ultra-low thermal expansion coefficient (55 x 10-7 K-1) was developed. The EYAP5 glass (80Al(PO3)3-20AlF3-1.5Er2O3-7.5Yb2O3, mol%) exhibits excellent spectral properties, thermomechanical properties, and chemical durability. Compared with traditional high phosphorus-doped silica glasses, EYAP5 glass achieves a higher Er3+/Yb3+ doping concentration and energy transfer efficiency from Yb3+ to Er3+ ions. Meanwhile, the absorption spectra, emission spectra, and fluorescence decay were systematically measured and compared in the temperature range of 300-480 K. Unlike the cases at 915 and 974 nm, the absorption cross section at 940 nm (-0.21 pm2) has the highest temperature stability, which facilitates the stable operation of the 1.5 mu m high-average-power laser. Furthermore, the temperature rises increase the energy transfer efficiency from Yb3+ to Er3+ ions, effectively suppressing the amplified spontaneous emission (ASE) at -1 mu m.