We have investigated temperature and doping dependence of fluorescence lifetime in Yb:YLF crystals in the 78–300 K range, for samples with Yb-doping levels of 0.5%, 1% and 25%. Radiation-trapping prolonged fluorescence lifetimes are first measured to understand the pros and cons of this inevitable process on fractional thermal load and laser gain. Later, pinhole method was used to acquire ideally trapping free fluoresce lifetimes. For the lowly Yb-doped samples, fluorescence lifetime was measured to be 1.97 ms and 2.1 ms at 78 K and 300 K, respectively. For the 25% Yb-doped sample, strong upconversion emission due to the presence of Er, Tm and Ho impurities were observed. A double-exponential decay behavior, combined with excitation intensity dependent decay profile was also revealed for this highly doped sample. Even with the pinhole method, the 300 K fluorescence lifetime was measured as 4.5 ms, showing the difficulty to acquire radiation-trapping free signals at high doping levels. Time dynamics of upconverted emission in different spectral regions were also recorded, which provides hints on the energy transfer mechanisms between the Yb ion and the other rare-earth impurities.

我们已经研究了Yb：YLF晶体在78–300 K范围内的温度和荧光寿命的掺杂依赖性，对于Yb掺杂水平为0.5％，1％和25％的样品。首先测量辐射陷阱延长的荧光寿命，以了解这种不可避免的过程在分数热负荷和激光增益方面的利弊。后来，使用针孔法获得了理想的捕获自由荧光寿命。对于低Yb掺杂的样品，在78 K和300 K下测得的荧光寿命分别为1.97 ms和2.1 ms。对于掺25％Yb的样品，由于存在Er，Tm和Ho杂质，观察到了强烈的上转换发射。对于这种高度掺杂的样品，还揭示了双指数衰减行为，与激发强度相关的衰减曲线相结合。即使采用针孔法，300 K荧光寿命测得为4.5 ms，这表明难以在高掺杂水平下获得无辐射俘获的信号。还记录了不同光谱区域上转换发射的时间动态，这为Yb离子与其他稀土杂质之间的能量转移机制提供了提示。