Acoustic fields and waves in solids vol 1

The left-hand (right-hand) block is of dimensions 150вЂ‰Г—вЂ‰110вЂ‰Ојm 2 (55вЂ‰Г—вЂ‰110вЂ‰Ојm 2) as seen from the top.

Silicon was chosen because of the relative ease of future sample preparation. The sample consists of a crystalline Si (100) substrate divided into three regions- two blocks and a connecting bridge- as shown in Fig. Furthermore, direct surface acoustic wave imaging techniques exist for this frequency range 21, 22, 23, 24, and so our work is therefore experimentally realizable. For both types of structure we choose microscopic sizes in order to give acoustic resonances in the gigahertz range, as such frequencies correspond to those used in surface acoustic wave filters and devices. With these structures we demonstrate transmission efficiencies up to ~23, calculated from the intensity enhancement over a region sampling the transmitted surface acoustic field. We also consider a bridge structure containing a resonant cavity. We first consider the case of a straight waveguide in the form of a deeply subwavelength-width bridge joining two blocks.

In this paper we demonstrate by means of numerical simulations the phenomenon of extraordinary transmission of surface acoustic waves in solids.

This is surprising in view of the potential simplifications introduced by reducing the dimensionality of the extraordinary transmission problem to waves confined to a plane, with potential applications in miniaturization of the overall geometry. However, in spite of the interesting possibilities in the fields of metamaterials and subwavelength imaging, the extraordinary transmission of surface waves, and in particular surface acoustic waves, has never been investigated. Experiments on the passage of Rayleigh waves through a fluid channel have demonstrated anomalously low acoustic transmission at certain frequencies 20. Several types of transmission mechanism were proposed for acoustic extraordinary transmission, in particular periodic-lattice resonances, Fabry-Perot-type resonances, elastic Lamb-mode-resonances, Helmholtz resonators, membrane resonances and space coiling. This was theoretically predicted for bulk waves 3, 4, 5, 6, 7, 8, 9 and experimentally verified in a wide variety of grating, slit and hole systems 10, 11, 12, 13, 14, 15, 16, 17, 18, 19. This work inspired extensive studies on the analogous extraordinary acoustic transmission phenomenon. The subject of extraordinary optical transmission through an array of subwavelength holes arose from measurements in the far infra-red and visible wavelength ranges in metal apertures 1, 2. Applications include new metamaterials and subwavelength imaging. We show how the cavity shape and bridge size influence the extraordinary transmission efficiency. intensity enhancements, up to ~23 and ~8 in the two respective cases. Several resonant modes of the structure, both one- and two-dimensional in nature, lead to extraordinary acoustic transmission, in this case with transmission efficiencies, i.e. By means of acoustic numerical simulations in the gigahertz range, corresponding to acoustic wavelengths О»вЂ‰~вЂ‰3вЂ“50вЂ‰Ојm, we track the transmission of plane surface acoustic wave fronts between two silicon blocks joined by a deeply subwavelength bridge of variable length with or without an attached cavity. Here we present a new class of extraordinary transmission for waves confined in two dimensions to a flat surface. a transmission superior to the amount predicted by geometrical considerations of the aperture alone, has to date only been studied in the bulk. Extraordinary transmission of waves, i.e.

Acoustic fields and waves in solids vol 1