Optical Generation of Coherent Ultrahigh Frequency Surface Waves

It has been demonstrated [1–4] that coherent bulk acoustic waves can be holographically induced by the interference pattern of two intersecting picosecond laser pulses. The coupling between the optical and elastic fields can either be due to electrostriction or optical absorption which produces thermal stresses. The resulting waveform can then be detected by a third time-delayed laser pulse which diffracts off the density grating of the wave field. The elastic response within the laser spot caused by either coupling mechanism has been shown to consist of 1-D counter-propagating pressure waves. From the frequency and attenuation of the diffracted signal, the wavespeed and attenuation coefficient, respectively, of the medium can be obtained