Surface acoustic wave generation with customized optical beam distributions

Diffractive acoustic elements for laser ultrasonics

“…In previous publications we have shown that this allows one to detect the ultrasonic distribution without averaging. 6,9 We have also shown how the increase in surface wave amplitude allows fast analog electronics to be used rather than a digital storage oscilloscope; this greatly improves the rate of image acquisition obtained in a noncontacting surface wave acoustic microscope. 9 The light distributions on the sample were obtained using a CGH, which produced a single arc.…”

“…The light from the source was then passed through different CGHs, which focused the beam onto the sample surface to form the profiles described throughout the paper. The resulting SAW distributions were detected with a specialized knife edge detector 6 which was mechanically scanned rela-tive to the sample, while the illumination optics remained fixed. The peak envelope of the ultrasonic tone bursts were normally acquired using the envelope detection electronics described in Ref.…”

“…We have reported previously on CGHs, which project an arc onto the surface of the sample, providing a diffraction-limited SAW ͑Rayleigh wave͒ focus. 5,6 These CGHs are analogous to using a refracting optical lens because they produce a continuous variation of the acoustic phase to effect the focusing. It is also possible to produce an analog of an optical diffractive CGH where control of the resulting beam is affected by discretely varying the phase of the ultrasonic source distribution.…”