Compared to earliest non destructive testing and evaluation methods based on transducers, laser ultrasonics shows specific advantages. It is a non-contact method combining a high spatial resolution and a large bandwidth, allowing high temperature and/or geometrically complex materials testing. In this work, ultrasonic waves are generated in an aluminium sample by a pulsed Nd:YAG laser in the thermoelastic mode. An interferometric optical probe is used to detect surface waves after their interaction with a flaw. This study will particularly focus on two Rayleigh waves. The first one is directly transmitted by the flaw whereas the second one is mode-converted from the head wave. Considering the relative amplitude of these two waves, experimental results lead to an original flaw depth gauging method.
