Abstract
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 I1018nm/I1534nm 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 I1018nm/I1534nm 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.
Highlights
In recent years, eye-safe 1.5 μm high-power fiber lasers have been extensively used in free-space communication, LIDAR, and range finding, which has attracted significant attention [1,2,3,4,5]
The ~15mol% P2 O5 was introduced in the Er3+/Yb3+ co-doped silica (EYPS) bulk glass, and the composition was close to that of the commercial erbium–ytterbium co-doped silica fiber (Nufern-LMA-EYDF25P/300-HE) [10]
Yb3+ ions and emission intensity ratio of I~1μm /I1534nm in the EYPS glass can be used to evaluate the efficiency of the energy transfer (ET) from the Yb3+ to the Er3+ ions [2,32]
Summary
Eye-safe 1.5 μm high-power fiber lasers have been extensively used in free-space communication, LIDAR, and range finding, which has attracted significant attention [1,2,3,4,5]. Doping high-concentration phosphorus is necessary for Er3+ /Yb3+ codoped silica fiber (EYDF) [10,11] This has two advantages, namely, an improved dispersion effect of the Er3+ and Yb3+ ions [12], and a weak back energy transfer (ET) from the Er3+ to. Two primary factors limit the increase in power of the EYDF: first, the significant thermal effect caused by the quantum defect (QD) [10,15,16], which reduces the pump absorption and damages the fiber coating [17,18,19]; second, the amplified spontaneous emission (ASE) and parasitic oscillations of the Yb3+ ions at ~1 μm, reducing the efficiency of the ET from the Yb3+ to the. The results provide sufficient data supporting the experimental design and modeling of the EYDF amplifier
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