Laser-generation of narrow-band surface waves

One of the factors limiting the application of laser-based ultrasonics for nondestructive evaluation, is the relatively low efficiency of ultrasound generation by laser illumination. The authors describe a method for improved narrowband surface wave generation by the use of a line focused laser and an array technique. A tone-burst-like surface wave has been generated by a diffraction grating, and a lens system. The system provides controllable center frequency by adjustment of the width and spacing of the lines of laser illumination in the array. It is demonstrated by the use of laser interferometer detection that the signal-to-noise ratio is significantly improved