We investigated an ablation impulse irradiated by a nanosecond laser with an Al planar and sphere target in a large beam spot. A torsion pendulum was developed to investigate single pulsed laser ablation impulses. A beam spot size of about 1 mm diameter was selected as the large spot size because investigations have proved that a beam spot size less than 420 μ m satisfied a one-dimensional plume expansion model. The results show that the minimum laser fluence corresponding to an observable ablation impulse of a planar target is about 3 J cm −2 , and the optimum laser fluence corresponding to the highest impulse coupling coefficient is about 10 J cm −2 for both large and small beam spots. Our investigations prove that these two parameters are independent of the beam spot size. The impulse investigation of a sphere-shaped target reveals that its overall impulse is lower than that of a planar one irradiated by a large laser beam spot in high laser fluence r...

中文翻译：

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纳秒级激光烧蚀在大束斑中激发平面和球形目标的脉冲

我们研究了纳秒级激光在大束斑中用Al平面和球形目标照射的烧蚀脉冲。开发了扭摆来研究单脉冲激光烧蚀脉冲。选择直径约1 mm的束斑作为大束斑，是因为研究证明束斑尺寸小于420μm满足一维羽状膨胀模型。结果表明，与平面目标的可观察到的烧蚀脉冲对应的最小激光通量约为3 J cm -2，与最大脉冲耦合系数对应的最佳激光通量无论大小均约为10 J cm -2。束斑。我们的研究证明这两个参数与束斑尺寸无关。