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Study of Picosecond Laser-Induced Shock Waves and Phase Transformation in Solids

皮秒激光诱导冲击波和固体相变的研究

基本信息

批准号：
01550005
负责人：
KANEMITSU Yoshihiko
金额：
$ 1.28万
依托单位：
University of Tsukuba (1990)Chiba University (1989)
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

项目摘要

1. GENERATION OF SHOCK WAVES STUDIED BY A PIEZOELECTRIC TRANSDUCERGeneration and propagation characteristics of picosecond laser-generated acoustic or shock waves in Si were studied by a ZnO transducer. In the Plasma formation region, the propagation velocity of acoustic pulses exceeds the sound velocity. At early stage of propagation. The amplitude of shock waves is affects by the formation and expansion of laser-generated plasma at the silicon surface.2. INTENSE ACOUSTIC WAVES IN GLASS STUDIED BY AN OPTICAL METHODLongitudinal waves propagate at the direction of the normal to the surface plane, but shear waves propagate at about 45 to the normal. At the early stage of propagation, the velocity of the wavefront exceeds the sound velocity in glass. Moreover, it is pointed out that the generation and propagation behavior of shear waves is very sensitive to the surface conditions.3. NEW PHOTOACOUSTIC SPECTROSCOPY USING A TRANSPARENT TRANSDUCERWe developed new photoacoustic spectroscopy system using a transparent transducer, and studied laser-induced structural changes at the surface of solids. The signal detected at the light-irradiated front surface has a large value and a good signal-to-noise ration compared with that at the back surface. Laser-induced surface structural changes are clearly observed using this system.4. SURFACE TRANSFORMATIONS AFTER HIGH-POWER LASER IRRADIATIONCrack formation in glass surfaces and explosive crystallization in a-Si were observed after high-Zower laser irradiation. The damage in the irradiated region was caused by laser ablation and plasma formation, but cracks and liquid drops also appeared outside the irradiated region over a distance of many millimeters. Delayed crack formation is caused by chemical reactions of component of glass with atmospheric water vapor at microcracks in the surface induced by laserーdriven shock waves. We also observed explosive crystallization of aーSi initiated by shock waves.

1.利用压电换能器研究了皮秒激光在Si中产生的声波或冲击波的产生和传播特性。在等离子体形成区域，声脉冲的传播速度超过声速。在繁殖早期。激光等离子体在硅表面的形成和膨胀影响冲击波的振幅.用光学方法研究玻璃中的强声波纵波沿表面法线方向传播，而横波则沿与表面法线约成45 °的方向传播。在传播的早期阶段，波前的速度超过玻璃中的声速。同时指出，横波的产生和传播对地表条件非常敏感.使用透明传感器的新型光声光谱我们开发了使用透明传感器的新型光声光谱系统，并研究了激光诱导的固体表面结构变化。在光照射的前表面处检测到的信号与在后表面处检测到的信号相比具有大的值和良好的信噪比。利用该系统可以清晰地观察到激光诱导的表面结构变化.高功率激光辐照后的表面转变观察到玻璃表面裂纹的形成和a-Si的爆晶化。在照射区域的损伤是由激光烧蚀和等离子体的形成，但裂纹和液滴也出现在照射区域以外的几毫米的距离。延迟裂纹的形成是由于玻璃组分与大气水蒸气在激光冲击波作用下产生的表面微裂纹处发生化学反应所致。我们还观察到了由冲击波引发的a-Si的爆炸结晶。