Shear-wave focusing with a laser-ultrasound phased-array

Pulsed laser arrays have been used to improve the beam parameters of laser generated ultrasound. The focusing and steering of shear-acoustic-wave beams generated by an array of thermoelastic sources has been investigated. A modeling of the impulse diffraction response of a single line source was derived from the point source model (Surface Center Of Expansion) of the thermoelastic source. The acoustic field launched by an array of point- or line-sources has been computed. Experimentally, the impulse response of a line source has been measured by using a heterodyne interferometer. It was shown with a 16-beam YAG laser, that shear-acoustic-wave beams can be focused and steered inside a duraluminum sample with a great efficiency.