Energy storage and dispersion of surface acoustic waves trapped in a periodic array of mechanical resonators

Abstract

International audienceIt has been shown previously that surface acoustic waves can be efficiently trapped and slowed by steep ridges on a piezoelectric substrate, giving rise to two families of shear-horizontal and vertically polarized surface waves. The mechanisms of energy storage and dispersion are explored by using the finite element method to model surface acoustic waves generated by high aspect ratio electrodes. A periodic model is proposed including a perfectly matched layer to simulate radiation conditions away from the sources, from which the modal distributions are found. The ratio of the mechanical energy confined to the electrode as compared to the total mechanical energy is calculated and is found to be increasing for increasing aspect ratio and to tend to a definite limit for the two families of surface waves. This observation is in support of the interpretation that high aspect ratio electrodes act as resonators storing mechanical energy. These resonators are evanescently coupled by the surface. The dispersion diagram is presented and shows very low group velocities as the wave vector approaches the limit of the first Brillouin zone

High quality broadband spatial reflections of slow Rayleigh surface acoustic waves modulated by a graded grooved surface

“…This indicates that the surface wave can be slowed down and stopped by the grooves and wave energy can be trapped as discussed in references. 18,22 In this paper we will show that the energy trapping for the incident wave is a very ideal situation for completely periodic structure and cannot be reached in the real application especially for the graded structures. When the grooves are deeper, the second-order curves of the eigenvalue results will cross the linear Rayleigh SAW dispersion curve shown in solid line in Fig.…”

“…[14][15][16][17][18][19][20][21][22] Especially, Rayleigh SAWs or sagittal SAWs modulated by one-dimensional periodic gratings 18,[22][23][24][25] have been investigated due to easy fabrication of the structures and inherent applications of the interdigital transducers. 17,26 However, most of these works are focusing on band gap property, transmission attenuation, slow wave effect, 18,22 etc. As far as the reflection problem of SAW, Wu's group 27,28 has proposed using phononic crystals as high efficiency compact reflective gratings and high performance resonant cavities based on the corresponding band gap characteristic.…”

Bandgaps and directional propagation of elastic waves in 2D square zigzag lattice structures

“…4. Perfectly matched layers (PMLs) [24] are used as extended domains at the artificial model domain boundaries to eliminate the unphysical wave reflections. PMLs have exactly the same elastic property and mass density as the matrix, but have an artificial gradient damping coefficient along the wave propagation direction.…”

Improving surface acousto-optical interaction by high aspect ratio electrodes

“…In order to plot the mode shapes, we introduced a finite element model of a piezoelectric anisotropic material in Ref. 12 to simulate the HAR electrodes utilizing periodic boundary conditions. A perfectly matched layer ͑PML͒ was employed at the bottom to absorb the mechanical and electrical disturbances propagating away from the surface.…”