Laser-induced ultrasonic waves in film-substrate system

Laser-induced ultrasonic waves in the film-substrate system are of considerable interest owing to their applications in nondestructive evaluation of the film and also the field of laser induced damage. In such a system, the process of the thermoelastic generation of ultrasound is not only related to the properties of the film but also to those of the substrate. In this paper, we develop a one-dimensional analytic solution of a two-layer structure for thermoelastic excited ultrasonic waves. The temperature fields and displacement fields in the film-substrate system are obtained and the effects of many parameters, including the thermal diffusion, the optical penetration and the ratio of the acoustic characteristic impedance of the film and the substrate, on the acoustic wave are discussed.