Negative-refraction imaging with two-dimensional phononic crystals

We report negative refraction imaging for acoustic waves in a two-dimensional phononic crystal. The sample consists of a triangular array of steel rods immersed in water. Both the observed negative refraction behavior and imaging effect are in excellent agreement with numerical simulations by the multiple scattering theory method. The existence of nearly circular dispersion surfaces for the phonic crystal sample means that the negative refraction is well defined for all angles of incidence, and very robust in its realization and application to focusing and imaging.