The efficiency of solar-pumped lasers (SPLs) is limited when the length of the laser medium is unsuitable. This is because superfluous regions in the laser medium introduce losses and contribute slightly to the stimulation of radiation in the laser resonator. Before designing an SPL, an appropriate length of laser medium is critical. We present a method to calculate the optimal length of the gain medium in SPLs by exploring the relationship between the absorbed solar power and material loss for different laser medium lengths. Thus, the lengths of Nd:YAG crystals with diameters of 3 to 6 mm were optimized, and the output characteristics were calculated numerically. The maximum collection efficiency (CE) (40.1 W / m2) was obtained for the 5.5-mm diameter Nd:YAG crystal rod of length 21.1 mm, which was 1.7 W / m2 higher than the previous numerical record. The optimal length of the 6-mm diameter Nd:YAG crystal rod was found to be 21.9 mm. For a laser rod of this length, a CE of 36.3 W / m2 is expected. This value is 1.13 times greater than the existing experimental record for the Nd:YAG crystal of the same diameter, which highlights the importance of optimizing the length of the laser rod.

中文翻译：

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太阳能泵浦激光功率对激光介质长度依赖性的研究

当激光介质的长度不合适时，太阳能泵浦激光器 (SPL) 的效率会受到限制。这是因为激光介质中的多余区域会引入损耗，并且对激光谐振腔中的辐射刺激有轻微贡献。在设计 SPL 之前，适当长度的激光介质至关重要。我们提出了一种通过探索不同激光介质长度下吸收的太阳能与材料损失之间的关系来计算 SPL 中增益介质的最佳长度的方法。因此，优化了直径为 3 至 6 mm 的 Nd:YAG 晶体的长度，并数值计算了输出特性。对于直径为 5.5 mm、长度为 21.1 mm 的 Nd:YAG 晶体棒，获得了最大收集效率 (CE) (40.1 W / m2)，为 1。比之前的数值记录高出 7 W/m2。发现 6 毫米直径 Nd:YAG 晶体棒的最佳长度为 21.9 毫米。对于这种长度的激光棒，预计 CE 为 36.3 W/m2。这个数值是现有同直径Nd:YAG晶体实验记录的1.13倍，凸显了优化激光棒长度的重要性。