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

Abstract

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 0.38 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.