Guiding acoustic waves with graded phononic crystals

By virtue of the flat-shaped dispersion surface, acoustic wave beams inside a phononic crystal can propagate in a self-collimated or non-diffractive way. In this paper, we show that the non-diffractively propagating acoustic beams can be further tuned, by design, to propagate in a curved path in a graded phononic crystal, which thus may be used as an alternative device to the waveguide in applications. An acoustic wave beam propagating inside a two-dimensional graded phononic crystal and bending by an angle of π6 is demonstrated by FDTD simulation.