Acoustic Surface Evanescent Wave and its Dominant Contribution to Extraordinary Acoustic Transmission and Collimation of Sound

Abstract

We demonstrate both theoretically and experimentally the physical mechanism that underlies extraordinary acoustic transmission and collimation of sound through a one-dimensional decorated plate. A microscopic theory considers the total field as the sum of the scattered waves by every periodically aligned groove on the plate, which divides the total field into far-field radiative cylindrical waves and acoustic surface evanescent waves (ASEWs). Different from the well-known acoustic surface waves like Rayleigh waves and Lamb waves, ASEW is closely analogous to a surface plasmon polariton in the optical case. By mapping the total field, the experiments well confirm the theoretical calculations with ASEWs excited. The establishment of the concept of ASEW provides a new route for the integration of subwavelength acoustic devices with a structured solid surface.

Effective impedance boundary optimization and its contribution to dipole radiation and radiation pattern control

“…Note that the dipole-like radiation phenomenon occurs when the wavelength (l ¼ 40 mm) is much larger than the period of the HRs (d ¼ 8 mm), which can be utilized to realize device miniaturization. As no sidelobes occur in the pattern, the pattern is not due to the excitation of the acoustic surface wave emerging only in the vicinity of the resonant transmission peak 20 . Actually, the dipole-like radiation pattern can occur in a very wide bandwidth, which is illustrated below.…”

“…It may seem that our system is similar to that of a single slit surrounded by finite, periodically perforated grooves; however, the experimental phenomenon and the mechanism of our system are quite different. The directional beam experimental report by Zhou et al 20 showed very strong fingerprints of the running surface wave scattered by the grooves [20][21][22] , and the directional beam occurred in a very narrow bandwidth. We verify that the dipole-like pattern radiation phenomenon in our samples arises from the effective boundary impedance adjustment.…”

Negative Refraction and Energy Funneling by Hyperbolic Materials: An Experimental Demonstration in Acoustics

“…A motion picture showing the frequency dependence of the emitted beam propagating in free space is presented in the Supplemental Material Movie S3 [7]. This is not the first demonstration of funneling of acoustic energy with perforated structures, but the previous one [14,15] and the phenomenon was obtained resonantly, using acoustic surface waves. Here, on the contrary, it is a nonresonant phenomenon and consequently its bandwidth is not strongly limited.…”

Finite element analysis of surface modes in phononic crystal waveguides

“…Novel phenomena have been investigated, for example, enhanced light-matter interaction, ultrafast acoustoplasmonic control, and sensing by evanescent surface acoustic waves (SAWs). [1][2][3][4] Phononic nanostructures could lead to a variety of potential applications, ranging from acoustic metamaterials, self-collimation, sound isolation, and heat management to compact acoustic waveguides. [5][6][7][8][9] Similar to their photonic counterparts, the flexibility to tailor the acoustic properties of phononic crystals (PnCs) and PnC waveguides makes them particularly suitable for a wide range of applications from transducer technology to filtering, guiding, and demultiplexing of acoustic waves.…”