High frequency acoustic dispersion of surface waves using time-resolved broadband microscopy

Broadband time-resolved microscopy was used in order to extend spatial frequency domain analysis of the V(z)-technique from a single frequency to the bandwidth of the transducer. With a special frequency dependent SAW speed imaging mode the occurrence and characteristics of the different SAW waves can be visualized. Phase velocities were estimated using multi-narrow-band spatial frequency analysis. A number of different plastics, metals, quartz glasses, piezo ceramics, tooth enamel, dentin and cortical bone was investigated. The observed velocities were in the range from 2300 to more than 6000 m/s. Recently reported multiple SAW reflections were only observed in low attenuating materials, e.g. titanium and aluminum. This methodology allows to study the frequency dependence of acoustic properties with a high spatial resolution and minor sample preparation, which is of particular interest for the investigation of biological materials.