Discrete propagation of trapped modes in acoustic waveguide arrays

Abstract : Arrays of evanescently coupled waveguides in which wave behavior becomes discretized exhibit unique wave dynamics, and they offer the possibility to investigate analogous fundamental quantum phenomena at accessible time and length scales. In this Rapid Communication, we investigate the discretelike propagation of trapped modes in airborne acoustic waveguide arrays. Using numerical simulations and experiments, we analyze the emergence of acoustic discrete diffraction and spatial Bloch oscillations in the array. Furthermore, exploiting the Bloch oscillations phenomenon, we demonstrate the possibility to generate diffraction-free acoustic beams and to focus the acoustic energy within a single lattice site at distances orders of magnitude larger than the operating wavelength.