周期变截面波导中的多缺陷态*

设计了一种具有对称结构的多缺陷周期变截面波导,并在其Bragg禁带中实现了多缺陷态的产生。研究表明,通过调整缺陷的个数和长度可实现对缺陷态数目的选择和缺陷态中心频率的调谐。另外,改变重复周期个数可对缺陷态的带宽进行调节。通过对各缺陷态的声场分布进一步分析,我们发现声压沿波导中心轴呈对称或反对称分布。对称缺陷态的最大声能量总是向长度较小的缺陷处偏移,而反对称缺陷态则相反,总是向长度较大的缺陷处偏移。利用这种偏移特性可实现对多缺陷态的声场调控。这不仅使我们对声缺陷态的认识更加深入,更有利于功能型声波导器件的发展与应用。

Multi-defect states in a waveguide with periodically corrugated walls

A multi-defect waveguide with periodically corrugated boundaries has been designed, and the multi-defect states in Bragg bands has also been studied. Numerical simulations show that the number of defect states can be changed by altering the number of inserted defects. The center frequency of defect states can be tuned by adjusting the length of defects and the bandwidth of defect state can be enlarged or narrowed when increasing or decreasing the number of repetition periods. According to the distribution of the sound pressure along the center of the waveguide, the multi-defect states can be classified into the symmetric and anti-symmetric defect states. The localized sound energy of the symmetric defect state always shifts to a shorter defect. And for the antisymmetric defect state, on the contrary, it always moves to a longer defect. These characteristics can be used to control the sound field of multi-defect states, which not only enriches our knowledge on sound defect states but also plays a very important role on the development of functional devices.