In this work, we have investigated six different in situ optical contactless temperature probing methods for cryogenic Yb:YAG systems. All the methods are based on variation of fluorescence spectra with temperature, and they either look at the width of the emission line, the ratio of the emission intensity at different wavelengths and to the overall spectral change at selected wavelength intervals. We have shown that, for Yb:YAG crystal with homogeneous temperature distribution, one can perform real-time contactless optical temperature measurements with a ± 1 K accuracy in the 78–300 K range. We have further tested the methods in measuring the average temperature of Yb:YAG rods at up to 500 W absorbed pump power level. We have seen that, a real-time temperature measurement accuracy of ± 5 K is feasible in both lasing and non-lasing situations for estimating the average temperature of crystals under nonhomogeneous thermal load. The techniques are quite valuable in evaluating the bonding quality of Yb:YAG crystals in cryogenic systems. Moreover, the real-time temperature information provides feedback on parameters like cavity alignment status and extraction efficiency to the laser engineers while optimizing the system.

在这项工作中，我们研究了用于低温 Yb:YAG 系统的六种不同的原位光学非接触式温度探测方法。所有方法都基于荧光光谱随温度的变化，它们要么着眼于发射线的宽度、不同波长下发射强度的比率以及选定波长间隔的整体光谱变化。我们已经表明，对于的Yb：YAG晶体具有均匀的温度分布，可以与执行实时非接触光学温度测量一个 ± 1 K 精度在 78–300 K 范围内。我们进一步测试了在高达 500 W 的吸收泵功率水平下测量 Yb:YAG 棒平均温度的方法。我们已经看到，± 5 K 的实时温度测量精度在激光和非激光两种情况下都是可行的，用于估计非均匀热负载下晶体的平均温度。这些技术在评估低温系统中 Yb:YAG 晶体的结合质量方面非常有价值。此外，实时温度信息在优化系统的同时向激光工程师提供有关腔对准状态和提取效率等参数的反馈。