We report on the experimental study of propagation surface guided waves in a periodic arrangement pillars semi-infinite medium. Samples composed nickel grown lithium niobate substrate were prepared and wide bandwidth transducers used for electrical generation elastic waves. identify complete band gap appearing at frequencies markedly lower than Bragg gap. Using optical measurements vibrations by comparison with finite element model, we argue that low frequency arises because local resonances...

We investigate theoretically the propagation of acoustic waves in a two-dimensional array cylindrical pillars on surface semi-infinite substrate. Through computation band structure periodic and transmission through finite length array, we show that phononic crystal can support number propagating modes nonradiative region substrate, or sound cone, as limited by slowest bulk wave. The modal shape polarization these guided are more complex than those classical homogeneous surface....

The complex band structure of a phononic crystal is composed both propagating and evanescent Bloch waves. Evanescent waves are involved in the diffraction acoustic phonons at interfaces finite structures. They shown to arise because gaps, where they directly measure exponential decrease upon transmission, frustrated nature higher-order diffracted low frequencies. These become propagative as frequency increases thus populating higher bands. results should apply well any periodic medium...

The regularity of earthquakes, their destructive power, and the nuisance ground vibration in urban environments, all motivate designs defence structures to lessen impact seismic waves on buildings. Low frequency waves, range $1$ $10$ Hz for earthquakes up a few tens vibrations generated by human activities, cause large amount damage, or inconvenience, depending geological conditions they can travel considerable distances may match resonant fundamental ultimate aim any metamaterial, other...

We investigate stop band properties of a theoretical cubic array iron spheres connected to bulk concrete via or rubber ligaments. Each sphere moves freely within surrounding air cavity, but ligaments couple it the and facilitate bending rotational motions. Associated low frequency local resonances are predicted by an asymptotic formula. find complete bands in range [16,21] Hz (resp. [6,11] Hz) for 7.4 m 0.74 m) diameter with 10 1 center-to-center spacing, when they steel rubber) The...

The confinement of waves in open systems represents a fundamental phenomenon extensively explored across various branches wave physics. Recently, significant attention is directed toward bound states the continuum (BIC), class modes that are trapped but do not decay an otherwise unbounded continuum. Here, theoretical investigation and experimental demonstration existence quasi-bound (QBIC) for ultrasonic achieved by leveraging elastic Fabry-Pérot metasurface resonator. Several intriguing...

The propagation of surface acoustic waves in two-dimensional phononic crystals pillars on a is investigated experimentally for hexagonal and honeycomb lattice symmetries. A random array also compared to the periodic crystals. Taking into account that geometrical physical characteristics are same all cases, it shown locally resonant band gap low frequency range almost independent periodicity resilient randomness. In contrast, Bragg disappears with array.

In metamaterial science local resonance and hybridization are key phenomena strongly influencing the dispersion properties; metasurface discussed in this article created by a cluster of resonators, subwavelength rods, atop an elastic surface being exemplar with these features. On metasurface, band-gaps, slow or fast waves, negative refraction dynamic anisotropy can all be observed exploring frequencies wavenumbers from Floquet-Bloch problem using Brillouin zone. These extreme...

We propose that wave propagation through a class of mechanical metamaterials opens unprecedented avenues in seismic protection based on spectral properties auxetic-like metamaterials. The elastic parameters these like the bulk and shear moduli, mass density, even Poisson ratio, can exhibit negative values stop bands. show here waves with frequencies ranging from 1 Hz to 40 be influenced by decameter scale version buried soil, combined effects impedance mismatch, local resonances Bragg More...

This study investigates the parametric analysis of a quarter-wave resonator integrated into brick structure for optimized acoustic isolation in buildings. Starting with 100 mm thickness and period, was designed parametrized. The optimization process yielded significant results, achieving an attenuation approximately -87 dB bandgap width 82%, surpassing -72.55 provided by mass law alone. These findings highlight potential to enhance isolation, making it promising solution noise control urban...

Rationally constructed materials have enabled access to optical capabilities beyond nature’s limitations, thanks advances made in both theory and experiment. These synthetic composites allow subwavelength confinement of electromagnetic energy facilitate unparalleled control over different aspects waves (polarization, amplitude, frequency, etc.). However, the diffraction phenomenon is severely hindering efficacy performance dielectric photonic components. Diffraction causes wave spread...

In every country on the globe, there are still actions to perform in order improve buildings' energy efficiency, particularly regions with severe weather conditions. Since walls heat-dissipating elements building, designing them effectively can help reduce consumption of HVAC (heating, ventilation, and air-conditioning) systems, which notorious for using excessive amounts energy. The use self-insulating construction materials relatively high thermal resistance low transmittance is most...

We observe experimentally the propagation of surface-guided waves in a hypersonic phononic crystal, both radiative and nonradiative regions spectrum. Combining electrical measurements reflection transmission as well optical maps surface displacement, band gap extending from 0.6 to 0.95 GHz is identified square lattice array 1 μm radius air holes milled lithium niobate. The reveal above gap, inside sound cone.

We investigate the polarization of Bloch waves in two-dimensional piezoelectric phononic crystals and crystal waveguides managed therein. It is found that addition to strong coupling induced for polarized plane periodic structuration, a weaker but non-negligible components originates from material anisotropy. Numerical illustrations are given an array air holes lithium niobate arranged according square lattice. observed when band mostly in-plane gets close out-of-plane, phenomenon repelling...

The theoretical study deals with the propagation of surface acoustic waves in two-dimensional arrays resonant elements different symmetry lattices. are cylindrical pillars on a semi-infinite substrate. obtained band structures show interaction resonances medium which form additional gaps that decoupled from Bragg gaps. Especially, frequency position lowest gap is invariant respect to lattice symmetries. Thereby, this independent pitch, unexpected based interferences. However, role period...

We explore interactions of elastic waves propagating in plates (with soil parameters) structured with concrete pillars buried the soil. Pillars are 2 m diameter, 30 depth and plate is 50 thickness. study frequency range 5 to 10 Hz, for which Rayleigh wave wavelengths smaller than This compatible ranges particular interest earthquake engineering. It demonstrated this paper that two seismic cloaks' configurations allow an unprecedented flow elastodynamic energy associated surface waves. The...

We experimentally demonstrate that a Duraluminium thin plate with thickness profile varying radially in piecewise constant fashion as h(r)=h(0)(1+(r/Rmax)2)2, h(0) = 0.5 mm, h(Rmax) 2 and Rmax 10 cm, behaves many ways Maxwell's fish-eye lens optics. Its imaging properties for Gaussian pulse central frequencies 30 kHz 60 are very similar to those predicted by ray trajectories (great circles) on virtual sphere (rays emanating from the North pole meet at South pole). However, refocusing time...

Periodic structures can be engineered to exhibit unique properties observed at symmetry points, such as zero group velocity, Dirac cones, and saddle points; identifying these the nature of associated modes from a direct reading dispersion surfaces is not straightforward, especially in three dimensions or high frequencies when several fold back Brillouin zone. A recently proposed asymptotic high-frequency homogenization theory applied challenging time-domain experiment with elastic waves...

Acoustic flat lensing is achieved here by tuning a phononic array to have indefinite medium behaviour in narrow frequency spectral region along the acoustic branch. This confirmed occurrence of band an unusual path Brillouin zone and interpreting intersection point isofrequency contours on corresponding surface; coherent directive beams are formed whose reflection from surfaces create lensing. Theoretical predictions corroborated time-domain experiments, airborne waves generated source with...