Subwavelength imaging of acoustic waves by a canalization mechanism in a two-dimensional phononic crystal

Abstract

In this letter, the subwavelength imaging of acoustic waves is reported based on a mechanism that the evanescent modes of a source are canalized by the Bloch modes of a two-dimensional phononic crystal that served as the lens. The phononic crystal was designed to have a thickness that meets the condition of Fabry–Pérot resonance in order to enhance wave transmission and hence to improve imaging performance. Numerical simulations demonstrated that for a point acoustic source an image as small as 0.16λ can be formed.

Frequency dependence of the acoustic field generated from a spherical cavity transducer with open ends

“…Inspired by the development of phononic crystals [12][13][14] and metamaterials, [15][16][17] acousticians have also achieved subwavelength focusing used in ultrasonic imaging. 18,19 Unfortunately, the acoustic intensity in the focal region obtained by these techniques is too weak to be used in therapeutic HIFU applications. Spherical acoustic resonators is a useful tools in studying the properties of gases and liquid.…”

Bandwidth and resolution of super-resolution imaging with perforated solids

“…[13][14][15][16][17][18][19][20][21][22] In fact, recent studies have also found that acoustic metamaterials can be very useful in super-resolution imaging. [23][24][25][26] These include the acoustic hyperlens and acoustic superlens. An acoustic hyperlens has been first proposed by Ao and Chan.…”

Acoustic guiding and subwavelength imaging with sharp bending by sonic crystal

“…Suitable designing of a SC gives the phenomenon called self-collimation, by which a beam of acoustic wave can propagate in SCs with almost no diffraction along a definite direction [1,2]. This interesting phenomenon, also reported in Photonic crystals (PCs) [3][4][5], affords a promising way to control the flow of waves, thus it has been utilized for various wave-functional applications, such as the wave beaming [6,7], subwavelength imaging [8,9] and wave guiding [10].…”

“…This type of waveguide does not depend on physical channels to confine waves, thus it gains many advantages over conventional line-defect based wave guides, for which introducing of physical boundaries in SCs or PCs leads to extra coupling loss and Fresnel reflection loss [3,5]. Moreover, profited from a long flat equifrequency contour (EFC), evanescent modes of a source placed at the input port of such waveguides can also be canalized to the output port [8,9], thus self-collimation waveguides possess a promising prospect in subwavelength applications. However, such wave guide is suffered from the intrinsic inability of self-collimation to efficiently bend and redirect waves.…”

“…The outer and inner radii of rubber are 0.429a and 0.398a respectively, where a is the lattice constant. The material parameters are mass and then undergo a self-collimated propagation along the ΓM direction around the frequency 0.115 [8,9]. In addition, as these eigenmodes have wave vector components parallel to the ΓX direction [ // q in Fig.…”