Acoustic Microscopy: Deep Focusing Inside Materials at Gigahertz Frequencies

Abstract

Another way of imaging inside materials using transverse modes generated at the liquid-sample interface is shown. These modes can be highly focused for a given depth by means of aspherical lenses which apodize the efficiency conversion. Calculations of the profile of these lenses are reported and experiments are performed at 500 MHz through standard silicon wafers. This technique is extended to other types of material and structures such as metal-metal and ceramic-metal bondings.