中文摘要：

基于二维六方晶格声子晶体的高对称性,通过裁剪声子晶体模型,实现声波自准直束60°和120°全反射弯曲,证实点源声波的准直弯曲和亚波长成像.在六方晶格声子晶体中引入线缺陷,实现自准直束的60°和120°弯曲及分裂,详细分析了缺陷尺寸对入射准直束的60°（或120°）弯曲声束与透射声束能量分配的影响.本文的工作可以使基于自准直效应的应用更加灵活.

英文摘要：

Self-collimation,a peculiar effect that allows acoustic signals to propagate in sonic crystals（SCs） along a definite direction with almost no diffraction,possesses a promising prospect in integrated acoustics as it provides an effective way to transmit acoustic signals between on-chip functionalities.There exists,however,the intrinsic inability of selfcollimation to efficiently bend and split acoustic signals.Most of existing schemes for bending and splitting of selfcollimated acoustic beams are based on SC of square lattice,thus their bending and splitting angles are restricted to 90°.In this paper,the finite element method is used to investigate self-collimation of acoustic beams in an SC of hexagonal lattice.It is shown that 60°and 120°bending of self-collimated acoustic waves can be simultaneously realized by simply truncating the two-dimensional hexagonal SC.Bended imaging for a point source with a subwavelength resolution of 0.38λ_0can also be realized by truncating the SC structure.In addition,a scheme for 60°and 120°splitting of selfcollimated acoustic waves is also proposed by introducing line-defects into the hexagonal SC.It is demonstrated that an incoming self-collimated beam can be split into a 60°（or 120°bended one and a transmitted one,with the power ratio adjusted by the value of defect size.We believe that this hexagonal-SC-based bending and splitting mechanism will offer more flexibilities to the beam control in the design of acoustic devices and will be useful in integrated acoustic applications.