Directivity patterns of a moving thermoelastic source in solid media.

Generation of ultrasonic displacements under the thermoelastic effect has the advantage of being contactless and nondestructive. Unfortunately, the directivity and energy of the sound field of such a source are limited. In order to change these parameters the authors use a moving thermoelastic source by moving the laser beam on the solid surface. Moving the laser beam allows control of the ultrasonic beam directivity and an increase in the energy of the sound field. For this purpose, a large impulse of dye laser deflected by an acoustooptic cell working under the Bragg mode is used. Experimental results, in an aluminum sample give good agreement with the theoretical prediction.