Simulation of laser-generated ultrasonic waves in layered plates

A model is presented for the pulsed laser generation of ultrasound in isotropic layered plates. The stresses and displacements of the plate have been formulated in the Hankel and Laplace transform domains using the Thompson transfer matrix approach. The time domain response has been obtained by numerically inverting the transforms. Several numerical results are presented showing the normal surface displacement in the following configurations: single-layer film on a semi-infinite substrate, two layers on a semi-infinite substrate, and three-layer plates. The model provides a useful tool for the determination of which modes are generated by a laser source in a layered system. It can also be used to determine how sensitive the modes are to small changes in density, thickness, or elastic properties of the layers and to help in the selection of experimental parameters (laser spot size, pulse length, and source to receiver distance) for optimal sensitivity.