We present a 2 μm Tm:YAG disk laser multi-pass pumped by a 1 μm laser. The transitions in competition of up conversion (UC) and excited state absorption (ESA) are analyzed in detail based on a numerical model that considers stimulated emission, fluorescence, non-radiative decay, UC, andESA, showing good agreement with experiments. The proportions and fractional thermal loads of all transitions are derived quantitatively. The results show that UC and ESA are critical in Tm:YAG disk lasers, resulting in a decrease in the absorbed pump power and temperature after lasing for two different disk thicknesses. In addition, although the absorbed pump power of the 0.5 mm disk is lower than in the 1 mm case, its relatively weak UC and ESA and low total fractional thermal load can improve laser performance. A 0.5 mm Tm:YAG disk laser thus delivered the maximum output power of1.05 W with beam quality of Mx2 = 2.02 and My2 = 2.03.

中文翻译：

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1 μm激光泵浦的Tm:YAG圆盘激光器多通道上转换和激发态吸收分析

我们提出了由 1 μm 激光器泵浦的 2 μm Tm:YAG 圆盘激光器多通道。基于考虑受激发射、荧光、非辐射衰变、UC和ESA的数值模型，详细分析了上转换（UC）和激发态吸收（ESA）的竞争跃迁，与实验结果吻合良好。所有转变的比例和分数热负荷都是定量得出的。结果表明，UC 和 ESA 在 Tm:YAG 圆盘激光器中至关重要，导致两种不同圆盘厚度激光发射后吸收的泵浦功率和温度降低。此外，虽然 0.5 mm 圆盘的吸收泵浦功率低于 1 mm 的情况，但其相对较弱的 UC 和 ESA 以及较低的总分数热负载可以提高激光器性能。0.5 毫米 Tm：米X2= 2.02 和米是的2= 2.03。