腔长调控Nd:YVO₄纳秒固体紫外激光器的输出特性研究

Study on the Output Characteristics of Nd:YVO₄ Nanosecond Solid-State Ultraviolet Laser with Tunable Cavity Length

摘要: 为探究谐振腔腔长对Nd:YVO₄纳秒激光器输出特性的影响，本文分别搭建210 mm、224 mm、269 mm、359 mm四种不同腔长的激光谐振腔，系统开展10~100 kHz重复频率(重频)范围内的激光输出实验，深入分析腔长对激光器平均功率、脉冲宽度、单脉冲能量、光束质量及泵浦工作特性的调控规律。实验结果表明：腔长显著改变激光器最优工作重频区间与输出性能，随着腔长增大，激光器峰值平均功率对应的最佳重复频率逐步向低频偏移，短腔(210 mm, 224 mm)适配中高重频工作场景，在60~70 kHz重频区间可维持稳定的功率输出与单脉冲能量；长腔(269 mm, 359 mm)具备更强的腔内储能优势，在30~40 kHz低重频下可获得更高的单脉冲能量，其中269 mm腔长激光器综合输出性能最优，在40 kHz重频下实现14.78 W的峰值输出功率，单脉冲能量达0.36 mJ，脉宽仅13.9 ns，光束质量因子接近1.1，束腰圆度可达96.3%。所有腔长工况下，激光器脉宽均随重频升高呈单调展宽趋势，单脉冲能量随重频提升持续衰减，符合声光调Q激光器典型输出特性。泵浦电流测试结果显示，谐振腔越短，腔稳定工作区间越宽，可承受更大泵浦电流，最佳工作电流随腔长缩短向大电流方向偏移。光斑形貌测试表明，各腔长在最优工况下均能实现高纯度基模高斯输出，无明显模式畸变与像散，谐振腔结构具备良好的工况适配鲁棒性。本研究明确了不同腔长激光器的最优工作区间与性能适配场景，可为工业级纳秒脉冲全固态激光器的腔型优化、参数匹配及工程化应用提供实验依据与技术支撑。

Abstract: In order to explore the influence of cavity length on the output characteristics of Nd : YVO₄ nanosecond laser, four kinds of laser resonators with different cavity lengths of 210 mm, 224 mm, 269 mm and 359 mm were built respectively. The laser output experiments in the range of 10-100 kHz repetition frequency (repetition frequency) were carried out systematically, and the regulation of cavity length on the average power, pulse width, single pulse energy, beam quality and pump working characteristics of the laser were analyzed in depth. The experimental results show that the cavity length significantly changes the optimal repetition frequency range and output performance of the laser. As the cavity length increases, the optimal repetition frequency corresponding to the peak average power of the laser gradually shifts to the low frequency. The short cavity (210 mm, 224 mm) is adapted to the medium and high repetition frequency working scene, and the stable power output and single pulse energy can be maintained in the repetition frequency range of 60-70 kHz. The long cavity (269 mm, 359 mm) has stronger intracavity energy storage advantages, and higher single pulse energy can be obtained at 30-40 kHz low repetition frequency. Among them, the 269 mm cavity length laser has the best comprehensive output performance. The peak output power of 14.78 W is achieved at 40 kHz repetition frequency. The single pulse energy is 0.36 mJ, the pulse width is only 13.9 ns, the beam quality factor is close to 1.1, and the beam waist roundness can reach 96.3 %. Under all cavity length conditions, the pulse width of the laser shows a monotonic broadening trend with the increase of the repetition frequency, and the single pulse energy continues to decay with the increase of the repetition frequency, which is consistent with the typical output characteristics of the acousto-optic Q-switched laser. The pump current test results show that the shorter the resonant cavity is, the wider the stable working range of the cavity is, and the larger the pump current can be withstand. The optimal working current shifts to the direction of large current with the shortening of the cavity length. The spot morphology test shows that each cavity length can achieve high-purity fundamental mode Gaussian output under optimal working conditions, without obvious mode distortion and astigmatism, and the resonant cavity structure has good working condition adaptation robustness. This study clarifies the optimal working range and performance adaptation scenarios of lasers with different cavity lengths, which can provide experimental basis and technical support for cavity optimization, parameter matching and engineering application of industrial nanosecond pulsed all-solid-state lasers.