Broad omnidirectional acoustic band gaps in a three-dimensional phononic crystal composed of face-centered cubic Helmholtz resonator network.

Broad omnidirectional band gaps in a three-dimensional phononic crystal consisting of a face-centered cubic array of spherical air voids connected by cylindrical conduits in solid background are numerically and experimentally demonstrated. With a low material filling fraction of 37.7%, the first bandgap covers 3.

Ultrasonic Gas Sensing by Two-Dimensional Surface Phononic Crystal Ring Resonators.

An acoustic ring resonator employing a two-dimensional surface phononic crystal is proposed for high-sensitivity detection in binary gas mixtures. Band analyses and frequency-domain simulations via the finite-element method reveal that a single band for spoof surface acoustic waves appears at ultrasonic frequencies around 58 kHz where modification of its dispersion due to varying gas composition results in a linear shift of the resonance frequency. The shift rate is -17.

Acoustic Tamm states of three-dimensional solid-fluid phononic crystals.

In this work, the existence and propagation of acoustic Tamm states at the interface of air and a face-centered cubic solid-fluid phononic crystal composed of spherical air voids interconnected by cylindrical air channels are demonstrated. Supercell band structure computations via the finite element method reveal surface bands for Tamm states on (100), (110), and (111) surfaces of the phononic crystal. The states decay sharply into the phononic crystal so that only a two-row slab is sufficient to guide them over the respective surfaces without leakage, as confirmed by finite element simulations.

Phononic crystal surface mode coupling and its use in acoustic Doppler velocimetry.

It is numerically shown that surface modes of two-dimensional phononic crystals, which are Bloch modes bound to the interface between the phononic crystal and the surrounding host, can couple back and forth between the surfaces in a length scale determined by the separation of two surfaces and frequency. Supercell band structure computations through the finite-element method reveal that the surface band of an isolated surface splits into two bands which support either symmetric or antisymmetric hybrid modes. When the surface separation is 3.

Acoustic waveguiding by pliable conduits with axial cross sections as linear waveguides in two-dimensional sonic crystals.

Pliable conduits composed of periodically arranged concentric aluminum tori in air, with their axial cross sections acting as linear waveguides in two-dimensional sonic crystals, are numerically shown to guide acoustic waves in three dimensions in a flexible manner. Waveguide band structures are obtained by exploiting axial symmetry in a super-cell approach through two-dimensional finite-element simulations under the periodic boundary conditions. One isolated band having a bandwidth of 19.

Refraction-based photonic crystal diode.

A system composed of air holes in a dielectric host to form two square photonic crystals, with the same orientation and lattice constant but different scatterer radii, making an interface along their body diagonals, is numerically demonstrated to facilitate unidirectional light transmission. Band structure computations are carried out via the plane wave expansion method, whereas finite-difference time-domain simulations are carried out to investigate the transient behavior. Unidirectional light transmission is achieved over two adjacent stop bands along the ΓX direction, which are circumvented in the forward direction by scaling down the wave vector and rotating the surface normal.

Pressure field of rectangular transducers at finite amplitude in three dimensions.

In this study, the nonlinear pressure fields of various sized rectangular transducers are modeled in three dimensions. The model was based on Aanonsen's model, which has earlier been presented for circular sources. The nonlinear wave propagation at finite amplitude is presented for square and rectangular type sources up to three harmonics.