The influence of laser source on generated surface acoustic waves
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摘要: 利用激光激发声表面波及光差分技术研究激光源对声表面波的影响。实验中利用了Nd∶YAG脉冲激光器激发超声,采用632nm的He-Ne激光器基于光束偏转法的光差分检测系统,测量了铝样品表面的声表面波,获得了很好的信号。在此基础上研究了激发源的形状和能量对激发的声表面波幅度的影响。同时从热弹和融蚀机制下讨论激光声表面波的产生。在这两种机制下,声表面波的幅度发生了很大的变化。随着激光能量密度的增加,声表面波的幅度由线性变化转换为非线性变化。这一结果对激光激发声表面波理论研究有一定的指导意义。Abstract: A laser generation and optical difference detection method of surface acoustic waves(SAW) is used to study the influence of laser source on SAW.SAW are excited employing a Nd∶YAG laser on sample aluminum plate and detected with an optical difference detection system based on optical beam deflection technique with a 632nm He-Ne laser.The experimental investigation of the influence of the type of laser source and line source energy on laser generated SAW is carried out.Furthermore,the generation of SAW is discussed from the principles of thermoelasticity and ablation.In these two principles,the amplitude of SAW takes a great change.With the increase of the incident power density,the amplitude of SAW changes from linear to nonlinear.These results provide powerful guidance for the theory research of laser generated SAW.
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