The rainbow trapping effect has been demonstrated in electromagnetic and acoustic waves. In this study, rainbow trapping of ultrasonic guided waves is achieved in chirped phononic crystal plates that spatially modulate the dispersion, group velocity, and stopband. The rainbow trapping is related to the progressively slowing group velocity, and the extremely low group velocity near the lower bou...

The propagation of acoustic waves in a phononic crystal slab consisting of piezoelectric inclusions placed periodically in an isotropic host material is analyzed. Numerical examples are obtained for a square lattice of quartz cylinders embedded in an epoxy matrix. It is found that several complete band gaps with a variable bandwidth exist for elastic waves of any polarization and incidence. In ...

Photonic and phononic crystals are metamaterials with repeating unit cells that result in internal resonances leading to a range of wave guiding and filtering properties and are opening up new applications such as hyperlenses and superabsorbers. Here we show the first, to our knowledge, 3D colloidal phononic crystal that is reconfigurable in real time and demonstrate its ability to rapidly alte...

Solid-solid phononic crystals (solid inclusions in a solid matrix) exhibit wider bandgaps than those observed with airsolid phononic crystals (air inclusions in a solid matrix). In a solid-solid phononic crystal operating in the low MHz range, it is essential to place release holes in the center of the inclusions to release devices from the substrate. It is necessary to release, and therefore s...

We show, by measuring the transmission through a phononic crystal (PC) plate (slab), the evidence of the existence of large phononic band gaps (PBGs) in twodimensional PCs made by a hexagonal (honeycomb) array of holes etched through a free standing plate of silicon (Si). A CMOS compatible fabrication process is used on a Si on insulator (SOI) substrate to realize the devices. More than 30dB at...

Existing investigations on imperfect phononic crystal beams mainly concern periodic multi-span beams carrying either one or two channel waves with random or deterministic disorder in span-length. This paper studies the two channel bending waves in phononic crystal beams consisting of many phases of materials with defects introduced as one structural segment having different cross-sectional dime...

A plane-wave-expansion method suited to the analysis of surface-acoustic-wave propagation in two-dimensional piezoelectric phononic crystals is described. The surface modes of a square-lattice Y-cut lithium niobate phononic crystal with circular void inclusions with a filling fraction of 63% are identified. It is found that a large full band gap with a fractional bandwidth of 34% exists for sur...

The complete phononic band gap (PnBG) of a phononic crystal (PnC) slab is used to efficiently and simultaneously confine both flexural and extensional (longitudinal) elastic vibrations in a resonator. The PnC structure is fabricated by etching a hexagonal (honeycomb) array of air holes in a silicon (Si) slab. Flexural and extensional acoustic modes in the structure are directly excited by a pie...

In this paper, we present a theoretical analysis of the propagation of acoustic waves through elastic and viscoelastic two-dimensional phononic crystal structures. Numerical calculations of transmission spectra are conducted by extending the finite-difference-time-domain method to account for linear viscoelastic materials with time-dependent moduli. We study a phononic crystal constituted of a ...

We study simultaneous photonic and phononic crystal slabs created in Z-cut lithium niobate membranes. Bandgaps for guided waves are identified using the three-dimensional finite element method (FEM). Three lattices are considered: the square, the hexagonal, and the honeycomb lattices. We investigate the evolution of band gaps as a function of geometrical parameters such as hole radius and membr...