高对称型声子晶体自准直弯曲及分束

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.

Bending and splitting of self-collimated beams in high symmetry sonic crystal

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 self-collimation to efficiently bend and split acoustic signals. Most of existing schemes for bending and splitting of self-collimated 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 ₀ can also be realized by truncating the SC structure. In addition, a scheme for 60° and 120° splitting of self-collimated 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.