Thickness-modulated one-dimensional periodic phononic crystal

We have studied the dispersion curves of the thickness-modulated one-dimensional (1D) periodic phononic crystal. The dispersion curves of acoustic wave propagating perpendicular to the surfaces of the models are calculated based on the plane wave expansion (PWE) method. By compared the band gaps in thickness-modulated structure with the simple periodic structure, we have found that the band gaps in simple periodic model split into many sub-band gaps when the thickness of media layer is modulated periodically. This can be explained that the thickness-modulated structure can be considered to be made up of many periodic structures with different lattice spacing. It provides flexible choices for real engineering requirement.