Real Time Imaging of Surface Acoustic Waves on Crystals and Microstructures

The use of acoustic pulses to image materials is well-known in echography or sonar applications. We are extending this field by generating point-excited sound pulses on solid surfaces with ultrashort laser pulses and imaging the resulting surface wave propagation in real time. To see the tiny vibrations of the surface, smaller in amplitude than the dimensions of a single atom, we use another set of laser pulses for scanned probing. The typical surface phonon wavelength is of the order of a few microns, corresponding to frequencies up to 1GHz. With such a system we can watch coherent acoustic wave packets in two dimensions rippling across crystal surfaces and microscopic landscapes. [DOI: 10.1143/JJAP.44.4292]