Surface guided waves in two-dimensional phononic crystals

With FDTD (finite-difference time-domain) calculations we study the acoustic waves propagating in a semi-infinite, two-dimensional (2D) periodic elastic structure, i.e., a 2D phononic crystal, with a flat surface together with a line defect. Specifically we search for the acoustic modes localized near the surface and at the same time confined inside the straight line defect, i.e., the surface guided waves. The surface assumed is perpendicular to the axis of circular cylinders (steel) embedded periodically in a background material (polymer). These surface guided waves found are unstable in general due to the interaction with bulk acoustic waves but can propagate the distances over several hundreds of lattice constants for a certain range of frequencies.