Enhanced control of light and sound trajectories with three-dimensional gradient index lenses
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In this article, the authors numerically study the focusing and bending effects of light and sound waves through heterogeneous isotropic cylindrical and spherical metamaterials and show that the control of light requires spatially varying anisotropic permittivity and permeability.Abstract:
We numerically study the focusing and bending effects of light and sound waves through heterogeneous isotropic cylindrical and spherical devices. We first point out that transformation optics and acoustics show that the control of light requires spatially varying anisotropic permittivity and permeability, while the control of sound is achieved via spatially anisotropic density and isotropic compressibility. Moreover, homogenization theory applied to electromagnetic and acoustic periodic structures leads to such artificial (although not spatially varying) anisotropic permittivity, permeability and density. We stress that homogenization is thus a natural mathematical tool for the design of structured metamaterials. To illustrate the two-step geometric transform-homogenization approach, we consider the design of cylindrical and spherical electromagnetic and acoustic lenses displaying some artificial anisotropy along their optical axis (direction of periodicity of the structural elements). Applications are sought in the design of Eaton and Luneburg lenses bending light at angles ranging from 90° to 360°, or mimicking a Schwartzchild metric, i.e. a black hole. All of these spherical metamaterials are characterized by a refractive index varying inversely with the radius which is approximated by concentric layers of homogeneous material. We finally propose some structured cylindrical metamaterials consisting of infinitely conducting or rigid toroidal channels in a homogeneous bulk material focusing light or sound waves. The functionality of these metamaterials is demonstrated via full-wave three-dimensional computations using nodal elements in the context of acoustics, and finite edge-elements in electromagnetics.read more
Citations
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Acoustic focusing by coiling up space
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3-D-Printed Microwave and THz Devices Using Polymer Jetting Techniques
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Physics of surface vibrational resonances: pillared phononic crystals, metamaterials, and metasurfaces.
Yabin Jin,Yan Pennec,Bernard Bonello,Hossein Honarvar,Leonard Dobrzynski,Bahram Djafari-Rouhani,Mahmoud I. Hussein +6 more
TL;DR: The history and development of pillared materials are overviewed, a detailed synopsis of a selection of key research topics that involve the utilization of pillars or similar branching substructures in different contexts are provided, and some perspectives on the state of the field are provided.
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Manipulation of transmitted wave front using ultrathin planar acoustic metasurfaces
TL;DR: In this article, a simple acoustic metasurface is designed and characterized, whose microstructure is constructed with a cavity filled with air and two elastic membranes on the ends of cavity.
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Underwater acoustic omnidirectional absorber
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TL;DR: In this article, a cylindrical, two-dimensional acoustic "black hole" design that functions as an omnidirectional absorber for underwater applications has been presented, where multiple scattering theory was used to design layers of rubber cylinders with varying filling fractions to produce a linearly graded sound speed profile through the structure.
References
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TL;DR: The authors' simulations show that a version of the lens operating at the frequency of visible light can be realized in the form of a thin slab of silver, which resolves objects only a few nanometers across.
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