title: Two-dimensional sonic crystals with Helmholtz resonators.
abstract: We present a type of sonic crystal composed with an array of two-dimensional Helmholtz resonators, which in the long-wave regime have both a high relative acoustic refractive index n and at the same time, a small acoustic impedance Z mismatch with air for airborne sound. We analyze the n and Z of such sonic crystals by finite-difference time-domain simulations, and by mapping our results to a corresponding electromagnetic (EM) model, and we find that our Helmholtz resonant sonic crystal has a bigger effective magnetic permeability mu than the conventional rigid-cylinder sonic crystal in its EM counterpart. As a result, a thin convergent lens with very good focusing effect is demonstrated based on our crystal.
authors.affiliation: Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China. xhhu@ust.hk
authors.forename: Xinhua
authors.initials: X
authors.lastname: Hu
authors.forename: C T
authors.initials: CT
authors.lastname: Chan
authors.forename: Jian
authors.initials: J
authors.lastname: Zi