A high phosphorus Er³⁺/Yb³⁺ co-doped silica (EYPS) fiber core glass was prepared using the sol-gel method combined with high-temperature sintering. The absorption spectra, emission spectra, and fluorescence decay curves were measured and compared in temperatures ranging from 300 to 480 K. Compared to 915 and 97x nm, the absorption cross-section at ~940 nm (~0.173 pm²) demonstrates a weaker temperature dependence. Hence, the 940 nm pump mechanism is favorable for achieving a high-power laser output at 1.5 μm. Additionally, the double-exponential fluorescence decay of Yb³⁺ ions and the emission intensity ratio of I_1018nm/I_1534nm were measured to evaluate the energy transfer efficiency from Yb³⁺ ions to Er³⁺ ions. Through the external heating and active quantum defect heating methods, the emission intensity ratios of I_1018nm/I_1534nm increase by 30.6% and 709.1%, respectively, from ~300 to ~480 K. The results indicate that the temperature rises significantly reduce the efficiency of the energy transfer from the Yb³⁺ to the Er³⁺ ions.

The influence of Tm-doped pedestal fiber splice on the output performance of a large-mode-area (LMA) Tm-doped fiber laser (TDFL) has been investigated. Arc-fusion induced refractive-index deformation leads to laser leakage from the core to the pedestal, resulting in a periodic decrease in the output power of TDFL. Based on the measured refractive-index of splice with different arc-fusion parameters, the influence of the Tm-doped pedestal splice on laser propagation was analyzed using the beam propagation method (BPM). The simulation results indicate that optimizing the arc-fusion parameters can improve the efficiency of laser coupling into the fiber core at the splice. Experimental comparisons were made to assess the impact of different arc-fusion parameters on laser performance. By optimizing arc-fusion parameters of the TDFL, the near-periodic power degradation is reduced effectively. A hundred-watt-level all-fiber TDF setup was established. Compared to the initial splice, the optical conversion efficiency increased from 39.6% to 48.4% and the beam quality factor M ² was reduced from 10.55 to 2.17 in the horizontal direction and from 11.89 to 2.26 in the vertical direction. Understanding these mechanisms behind the abnormal power fluctuations hold practical value for the design of TDF pedestal fiber and further power scaling.