Laser-generation of directional surface acoustic wave pulses in metals

Abstract A technique is presented for the generation of directional beams of ultrasonic Rayleigh waves in metals. A pulsed thermoelastic line-source of Rayleigh waves is produced by line-focusing Q-switched Nd: YAG laser pulses onto metal surfaces with a cylindrical lens. Ultrasonic frequency components of the resultant Rayleigh waves, detected by resonant PZT probes, are shown to be emitted preferentially broadside from the line-source in narrow beams. The directional characteristics of the beams are presented. Corresponding theoretical expressions are developed to describe the directivity pattern, and are found to be in good agreement with experimental results.