Acoustic confinement and waveguiding in two-dimensional phononic crystals with material defect states

In this paper, we present the theoretical investigation of acoustic confinement and waveguiding in two-dimensional phononic crystals with material defect states. In contrast to the typical formation pattern of defect states, the proposed material defect states are created by replacing single cylinder in the core center or one row of cylinders in the perfect phononic crystal with different material cylinders. The dispersion relations and the power transmission spectra are studied by using the finite element method in combination with a supercell technique. With the introduction of material defects into perfect phononic crystals, defect states and bands appear, elastic waves of specific frequencies are localized in the point defects or along the line defects, respectively. The displacement fields of the eigenmodes are carried out to further intuitively illustrate the acoustic confinement and waveguiding in the material defect states phononic crystals. Furthermore, the effects of the material parameters of defects on the point defect states and waveguiding are further explored numerically. Numerical results show that, the location and number of defect states can be efficiently modulated by the material parameters of defects. The material defect states are more sensitive to the density parameters than the elastic constants when the elastic modulus of the defects is far higher than that of matrix.