脉冲Nd:YAG激光烧蚀石墨的反应性光声谱研究

应用脉冲宽度为400μs的自由振荡Nd:YAG激光器对石墨进行烧蚀并且检测烧蚀的反应性声谱。烧蚀声谱存在典型的双峰结构并且该声谱与光声腔长度无明显关系。烧蚀程度越大,与烧蚀相关的烧蚀声峰衰减越强烈,烧蚀声峰的上升时间约为400μs。当光斑直径为1.10mm时,激光能量从320mJ下降到150mJ,烧蚀声峰下降时间从3 ms上升到8 ms,石墨的烧蚀光能约为65mJ。烧蚀声峰值与光能量成正比。EMS分析烧蚀斑表明石墨的气化导致了烧蚀声谱的双峰结构和在烧蚀孔的内表面上有与光束正交的波纹状表面。

Study ot Reactivity Photoacoustic Spectra of Graphite in Ablation bya Pulsed Nd:YAG Laser

Graphite was ablated by a 400 us free-runing Nd:YAG laser and the reactivity photoacoustic spectra of ablation were detected . The acoustic spectra of ablation have a special double peak structure which does not depend on the length of the photoacoustic cell. The heavier the ablation is, the faster attenuation the ablating acoustic spectrum has. The rising time of the sound crest of ablation is about 400 us. With a 1. 10 mm diameter light spot on the surface of graphite, if the laser energy decreases from 320 mJ to 150 mJ, the attenuating time of the sound crest of ablation increases from 3 ms to 8 ms, and the critical ablating energy of graphite is about 65 mJ. The peak value of the sound crest of ablation is directly proportional to laser energy. According to the analysis of the ablated spots by EMS, vaporization of graphite leads to double peaks in the acoustic spectrum and the corrugated surface on the inside surface of the ablated hole.