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在大功率激光远距离定向传输中,远场发散角是衡量其性能的一个重要参量。大功率TEA CO2激光具有功率高、光束直径大等特点,常规手段无法准确测量其远场发散角。为解决该难题,提出了一种利用激光光斑尺寸拟合分析法来评估大功率TEA CO2激光的远场发散角。首先,从理论上推导大Fresnel数多模高斯激光束远场发散角,分析了影响激光束发散角的主要因素;然后,采用光斑烧蚀法试验测量近场(≤20 m)光斑数据,基于光束质量(M2)因子理论拟合得出了激光光束质量和束腰大小,从而推导出激光束远场发散角;最后,对比分析了以上两种方法的计算结果,讨论了结果存在偏差的原因。结果表明,近场光斑数据拟合法可准确、便捷地测量大功率TEA CO2激光束远场发散角。
In high-power laser long-range directional transmission, the far-field divergence angle is an important parameter to measure its performance. High-power TEA CO2 laser with high power, large beam diameter and other characteristics, conventional means can not accurately measure the far-field divergence angle. In order to solve this problem, a method of laser spot size fitting analysis was proposed to evaluate the far-field divergence angle of high-power TEA CO2 laser. Firstly, the far-field divergence angle of multi-mode Gaussian laser beam with large Fresnel number is theoretically deduced, and the main factors that affect the divergence angle of laser beam are analyzed. Then, the near-field (≤20 m) spot data are measured by spot ablation method. The laser beam quality and waist size are obtained by theoretical fitting of the beam quality (M2) factor, and the far-field divergence angle of the laser beam is derived. Finally, the calculation results of the above two methods are compared and the reasons for the deviation of the results are discussed . The results show that the near field spot data fitting method can accurately and conveniently measure the far field divergence angle of high power TEA CO2 laser beam.