Resumen:
Metamaterial acoustic lenses are acoustic devices based on phononic crystal structures that take advantage of negative or
near-zero indices of refraction. These unique properties arise due to either the antiparallel direction of the phase and
group velocity or strongly anisotropic dispersion characteristics, usually above the first transmission band. In this study,
we utilize an FDTD program to examine two phononic lenses that utilize anisotropic effects available in their second
band to collimate and focus acoustic waves from a plane-wave source with a k00 wavevector. The phononic crystals
consist of stainless steel rods arranged in a square lattice with water as the ambient material. Results show collimation
and focusing in the second band for select frequencies, fc 卤 0.005𝑓𝑐.