Defect states in three-component phononic crystal

Using the supercell plane wave method, we investigated the effect of the third component material as defects modifying band structure of two-dimension two-component phononic crystal (PC). It is shown that adding the third material as point defect/linear defects in the two-component PC, defect states/bands can appear in the original band gap whose position and width would have only minor changes. The frequency of the defect states/bands are affected by the third material's characteristics; and all the defect states are localized. Therefore, adding proper third material as point/linear defects to the two-component system with wide band gap where defect states/bands will fall in, some special filtered/guided states will be formed. This property has important significance in acoustic /elastic wave propagating and new acoustic applications.