Effective permittivity of dielectric honeycombs

Smith, F.C.

doi:10.1049/ip-map:19990392

Cited by 37 publications

(23 citation statements)

References 5 publications

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“…[ 16 ] However, negative Poisson's ratio materials with nanoscale lattice para meters cannot be fabricated using such techniques due to their limited resolution and the complexity of auxetic designs. Nevertheless, nanoscale auxetics would be particularly interesting as optical materials, considering that the combination of transformation optics concepts [ 20 ] with dielectric properties of auxetic meta materials [ 19,[21][22][23][24][25] already promises better electromagnetic cloaking devices for microwaves. [ 26,27 ] Here, we realize micro-and nanoscale metamaterial structures and demonstrate negative Poisson's ratios by mechanical actuation ( Figure 1 ).…”

Section: Doi: 101002/adma201600088mentioning

confidence: 99%

Nano‐ and Micro‐Auxetic Plasmonic Materials

et al. 2016

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and epoxy-resin casting.[ 19 ] Soft lithography, [ 12 ] femtosecond laser ablation, [ 13 ] and digital micromirror device projection printing [ 14 ] have allowed the fabrication of negative Poisson's ratio structures with characteristic sizes of hundreds of micrometers. Smaller dielectric auxetics with unit cells on the order of 100 µm have been made by laser micromachining, [ 15 ] while dielectric auxetics with a characteristic size of 10 µm have been realized by direct laser writing. [ 16 ] However, negative Poisson's ratio materials with nanoscale lattice para meters cannot be fabricated using such techniques due to their limited resolution and the complexity of auxetic designs. Nevertheless, nanoscale auxetics would be particularly interesting as optical materials, considering that the combination of transformation optics concepts [ 20 ] with dielectric properties of auxetic meta materials [ 19,[21][22][23][24][25] already promises better electromagnetic cloaking devices for microwaves. [ 26,27 ] Here, we realize micro-and nanoscale metamaterial structures and demonstrate negative Poisson's ratios by mechanical actuation ( Figure 1 ). Our nano-auxetic metamaterials are based on the re-entrant honeycomb design, which is known for auxetic properties for a wide range of beam thicknesses, sizes, and angles. [ 11 ] Inspired by recent work in the fi eld of nanomechanical photonic devices, [ 28 ] nanomembrane technology was used to fabricate auxetics with lattice parameters in the range from a few micrometers to hundreds of nanometers. Nanomembrane technology has already provided simple and effi cient solutions for reconfi guration of nanoscale structures that are not auxetic, enabling nanomechanical devices and sensors. In particular, engineered resonant optical properties and anisotropic light modulation with up to 50% optical contrast has been demonstrated with reconfi gurable metamaterials actuated by thermal, [ 29 ] electric, [ 30 ] and magnetic [ 31 ] signals, and fabricated from plasmonic-thin-fi lm-coated nanomembranes.The auxetic materials are shown by Figure 2 and were fabricated by thermally evaporating a 60 nm-thick gold plasmonic layer on a commercially available silicon nitride membrane of 50 nm thickness and then milling the re-entrant honeycomb structure through both layers using a gallium-focused ion-beam system (Helios 600 NanoLab by FEI). All structures were milled with an ion-beam energy of 30 keV. Infrared auxetic metamaterial microstructures were fabricated with 70 pA ion-beam current and a spot size of 21 nm, while nano-auxetic structures were milled with a reduced ion current of 9 pA and a smaller spot size of 12 nm. The honeycomb pattern has a rhombic unit cell and wallpaper symmetry group cmm . [ 32 ] For simplicity, we specify the smallest rectangular cell, p x × p y , that describes each structure, where the periodicities p x and p y along x and y correspond to the diagonals of the elementary rhombic unit cell, see Auxetics, materials with a negative Poisson's ratio, are rare in nature. ...

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Section: Doi: 101002/adma201600088mentioning

confidence: 99%

Nano‐ and Micro‐Auxetic Plasmonic Materials

et al. 2016

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“…See Figure 1. In the low frequency limit (i.e., when the honeycomb pitch p « X/2) the effective dielectric constant can be expressed as a diagonal tensor [9]. Using a numerical technique [10] to obtain the effective dielectric constant for a honeycomb structure, Smith [9] has yielded the following empirical relations for the real part of the effective dielectric tensor for the xx and yy components:…”

Section: Effective Medium Theorymentioning

confidence: 99%

Compact radiative control structures for millimeter astronomy

et al. 2010

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We have designed, fabricated, and tested compact radiative control structures, including antireflection coatings and resonant absorbers, for millimeter through submillimeter wave astronomy. The antireflection coatings consist of micromachined single crystal silicon dielectric sub-wavelength honeycombs. The effective dielectric constant of the structures is set by the honeycomb cell geometry. The resonant absorbers consist of pieces of solid single crystal silicon substrate and thin phosphorus implanted regions whose sheet resistance is tailored to maximize absorption by the structure. We present an implantation model that can be used to predict the ion energy and dose required for obtaining a target implant layer sheet resistance. A neutral density filter, a hybrid of a silicon dielectric honeycomb with an implanted region, has also been fabricated with this basic approach. These radiative control strictures are scalable and compatible for use large focal plane detector arrays.

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“…Provided and are not large, the values of , and are linearly related to and [5]. The effect on a conventional honeycomb of increasing or is simultaneously to increase , and ; , and cannot be varied independently.…”

Section: Electromagnetic Properties Of Re-entrant Dielectric Honmentioning

confidence: 99%

“…The facet arrangement of a conventional honeycomb limits the structural and electromagnetic properties which can be obtained from an array of honeycomb unit cells [5], [6]. From the electromagnetic viewpoint, a conventional honeycomb is always uniaxially anisotropic and the only effect of changing the honeycomb's unit cell properties is simultaneously to scale all three permittivity components [5].…”

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The electromagnetic properties of re-entrant dielectric honeycombs

Smith

Scarpa

Chambers

2000

IEEE Microw. Guid. Wave Lett.

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Abstract-Dielectric honeycombs are cellular materials often used in applications that require structural and electromagnetic characteristics, e.g., in LO (low observable) and radome components. A re-entrant (or auxetic) honeycomb is a cellular material with structural properties that are superior to those of a conventional honeycomb. By employing the finite-difference time-domain (FDTD) technique with periodic boundary conditions, the electromagnetic properties of re-entrant honeycombs are determined and compared to those of a conventional honeycomb. Re-entrant honeycombs are shown to have substantially superior electromagnetic properties. Measured permittivity data are used to substantiate the conclusions based on predicted FDTD data. The use of re-entrant honeycombs, rather than conventional honeycombs, in LO and radome applications can yield improved structural and electromagnetic performance.

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Effective permittivity of dielectric honeycombs

Cited by 37 publications

References 5 publications

Nano‐ and Micro‐Auxetic Plasmonic Materials

Nano‐ and Micro‐Auxetic Plasmonic Materials

Compact radiative control structures for millimeter astronomy

The electromagnetic properties of re-entrant dielectric honeycombs

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