An Efficiency Study of Laser-Induced Thermoelastic Wave Generation in Layers

The elastic wave generation and the efficiency of the thermal-to-mechanical energy conversion process of elastic wave generation by laser excitation are studied. A previously developed transfer matrix formulation [3, 4] is reviewed and the transient response in a silicon layer is computed by employing FFT. The transient thermal and mechanical response of a layer are considered, and the transient temperature, stress, acceleration and mechanical power are obtained under micro-second level excitation. The generation efficiency for the elastic wave components, which are utilized to evaluate the state of layered structures, is examined for a silicon layer. The results presented are useful in determining instrument specification, such as laser power, receiver dynamic range, and test set-up design.