Temporal behavior of the high-power pulsed gas terahertz laser pumped by a fundamental mode TEA CO2 laser
Temporal behavior of the high-power pulsed gas terahertz laser pumped by a fundamental mode TEA CO2 laser
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基模 TEA CO2 激光器泵浦的高功率脉冲气体太赫兹激光器的时间行为
DOI：
10.1364/oe.470793
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发表时间：
2022
期刊：
影响因子：
3.8
通讯作者：
Kun Yang
中科院分区：
文献类型：
--
作者：
Lijie Geng;Ruiliang Zhang;Pengji Yan;Yanchen Qu;Zhikun Ji;Yusheng Zhai;Weijiang Zhao;Zhifeng Zhang;Wenyan Zhang;Kun Yang
光抽运气体分子太赫兹（THz）激光器有望产生高功率和高光束质量的相干太赫兹辐射。然而，对于脉冲气体太赫兹激光器，很少研究输出太赫兹脉冲的时间行为。本研究首次在模拟和实验中获得了基模TEA CO2激光器泵浦的脉冲气体太赫兹的时间特性。采用基于密度矩阵速率方程的激光动力学模型，模拟了脉冲气体太赫兹激光器在不同气体压力下的时间行为和输出脉冲能量。结果清楚地表明，工作气体压力和泵浦脉冲能量对输出太赫兹脉冲形状有关键影响。得到了三种典型的脉冲形状，并基于激光动态过程对增益开关引起的太赫兹脉冲分裂进行了定量模拟和解释。此外，在342 mJ的入射泵浦脉冲能量下，在385µm处获得了2.31 mJ的最大输出太赫兹脉冲能量，对应的光子转换效率约为56.1%，这是我们所知道的D2O气体太赫兹激光器的最高效率。实验结果与整个工作压力范围内的数值模拟结果吻合较好，表明该模型为大功率脉冲气体激光器的设计和优化提供了有力的工具。
Optically pumped gas molecular terahertz (THz) lasers are promising for generating high-power and high-beam-quality coherent THz radiation. However, for pulsed gas THz lasers, the temporal behavior of the output THz pulse has rarely been investigated. In this study, the temporal behavior of a pulsed gas THz pumped by a fundamental-mode TEA CO2 laser has been presented for the first time both in simulation and experiment. A modified laser kinetics model based on the density matrix rate equation was used to simulate the temporal behavior and output pulse energy of a pulsed gas THz laser at different gas pressures. The results clearly show that the working gas pressure and pump pulse energy have critical influences on the output THz pulse shape. Three typical pulse shapes were obtained, and the THz pulse splitting caused by gain switching was quantitatively simulated and explained based on the laser dynamic process. Besides, with an incident pump pulse energy of 342 mJ, the maximum output THz pulse energy of 2.31 mJ was obtained at 385 µm, which corresponds to a photon conversion efficiency of approximately 56.1%, and to our knowledge, this is the highest efficiency for D2O gas THz laser. The experimental results agreed well with those of the numerical simulation for the entire working gas pressure range, indicating that our model is a powerful tool and paves the way for designing and optimizing high-power pulsed gas lasers.