二维声子晶体点缺陷间的耦合特性

Coupling characteristics of point defects in 2-D Phononic Crystals

以二维铝圆柱/空气正方格子声子晶体为研究对象,采用平面波法结合超元胞的方法研究了点缺陷间的耦合特性.结果表明,在(1 0)或(0 1)方向,两点缺陷因耦合将造成缺陷模的分离,分离宽度随两点缺陷距离的增加而减小,同时缺陷附近模场的分布也发生变化;在(1 1)方向因局域声子声场的迅速衰减而使局域声子间的耦合非常弱,即使缺陷间的距离非常小.局域声子的这些耦合特性在声方向滤波器、窄带声波导方面将有很大的应用价值.

Coupling characteristics between point defects in a 2-D phononic crystal composed of 2-D aluminum cylinders/air square lattices were studied using the plane-wave and super cell methods. The results indicate that, in the cases of （1 0） or （0 1）, two defected points separate the defected modes owing to the coupling and separating width decreasing with increasing distance between two defected points while the distribution of the mode field near defects changes. In the case of （1 1）, coupling between local phonons is very weak because the sonic field of localized phonons decays quickly even if the distance between defects is very small. These characteristics of coupling between localized phonons are referential to the research on directional sonic filters and narrowband sonic waveguides.