薄膜-基片中的激光超声研究

Laser-induced ultrasonic waves in film-substrate system

薄膜－基片中的激光超声研究对于薄膜的无损评价和检测以及薄膜的激光损伤等实际应用有很重要的作用。薄膜－基片系统中的激光热弹激发超声的过程不仅与薄膜性质有关,同时也与基片性质有关,因此,对于这样一个两层系统的激光超声研究要比单层材料的研究复杂得多。本文分别用光穿透模型和热扩散模型对薄膜－基片这一两层系统的激光热弹激发超声的过程进行研究,得到了薄膜和基片中的温度场和位移场分布的解析解。同时详细讨论了薄膜材料的光穿透参数、热扩散参数及基片和薄膜的特性阻抗比对激光超声波的影响。

Laser-induced ultrasonic waves in the film-substrate system are of considerable interest owing to their ap-plications in nondestructive evaluation of the film and also the field of laser induced damage. In such a system, theprocess of the thermoelastic generation of ultrasound is not only related to the properties of the film but also to thoseof the substrate. In this paper, we develop a one-dimensiona1 analytic so1ution of a two-layer structure for thermoelasticexcited u1trasonic waves. The temperature fields and displacement fields in the film-substrate system are obtained andthe effects of many parameters, including the thermal diffusion, the optical penetration and the ratio of the acousticcharacteristic impedance of the film and the substrate, on the acoustic wave are discussed.