Search results for "Metamaterial"

Conditions for achieving invisibility of hyperbolic multilayered nanotubes

2016

Invisibility of nanotubes has recently been demonstrated in highly anisotropic metamaterials in the transition regime from hyperbolic to elliptic dispersion [Sci. Rep. 5 (2015) 16027]. In such study, the characterization of a realistic multilayered metamaterial was carried out by means of an effective medium approach providing average components of the permittivity tensor and wave fields. Here, the edge effects of the metal-dielectric stratified nanotube for different combinations were thoroughly analyzed. We show how the boundary layers, which in principle remain fully irrelevant in the estimation of the effective permittivity of the nanotube, however play a critical role in the scattering…

Zero permeability and zero permittivity band gaps in 1D metamaterial photonic crystals

2007

We consider layered heterostructures combining ordinary positive index materials and dispersive metamaterials. We show that these structures can exhibit a new type of photonic gap around frequencies where either the magnetic permeability \mu or the electric permittivity \epsilon of the metamaterial is zero. Although the interface of a semi-infinite medium with zero refractive index (a condition attained either when \mu= 0 or when \epsilon= 0) is known to give full reflectivity for all incident polarizations, here we show that a gap corresponding to \mu = 0 occurs only for TE polarized waves, whereas a gap corresponding to \epsilon = 0 occurs only for TM polarized waves. These band gaps are …

Optical pulling and pushing forces in bilayer PT-symmetric structures

2018

Photons are massless, yet can exert force on small particles. This $r\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n$ $p\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}e$, though discussed by Kepler, still needs investigation for modern systems. This study reveals that the optical force exerted on a parity-time-symmetric bilayer with balanced gain and loss can be $a\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}y\phantom{\rule{0}{0…

Control of Space-Time Trajectories of Noise-Driven Optical Extreme Events in Metamaterial Waveguides

2019

Metamaterials offer the potential to precisely manipulate electromagnetic wave propagation in ways that cannot be achieved with materials found in nature. The formation and propagation of optical spatial solitons in metamaterials has been already investigated [1]. Here we report the theoretical and numerical investigations on temporal-spectral dynamics of nonlinear extreme events arising from the initial noise-perturbed plane wave in metamaterial waveguides. A typical waveguide structure used here is a planar structure with a metamaterial core and a part of the structure, in the form of the substrate, is replaced with a magnetooptic material. We assume that the core material is isotropic an…

Energy flow canalization of evanescent cylindrical-vector beams

2013

We analyzed ultra-confined vector beams with radial and azimuthal polarizations which are critically self-governed inside plasmonic metamaterials. We succeeded in the separation of polarization singularities in the fields at the nanoscale. The examined metamaterials are suitable for long-range transport of subwavelength Bessel beams without discernible blurring. These results open the door to develop integrated devices for applications such as the manipulation of polarization and angular momentum of surface-plasmon excitations.

Uniaxial epsilon-near-zero metamaterials: from superlensing to double refraction

2014

We investigated optical properties of nanostructured metal-dielectric multilayered lattices under the conditions of epsilon-near-zero (ENZ), a concept derived from the effective-medium approach (EMA). We theoretically found that the periodic array of metallic nanolayers may exhibit either superlensing driven by broadband canalization from point emitters or single-polarization double refraction, and conventional positive as well as negative, even at subwavelength regimes. For the latter case, we formulated a modified EMA, and subsequently a generalized refraction law, that describes both refractive behaviors concurrently. The modal coupling of plasmonic lattice resonances, and nonlocality in…

When size matters

2017

That the unit cell of a metamaterial can't be considered vanishingly small like in ordinary crystals has long been deemed more burden than opportunity. The emergence of a characteristic length scale in metamaterial chains may change that trend.

Static chiral Willis continuum mechanics for three-dimensional chiral mechanical metamaterials

2019

International audience; Recent static experiments on twist effects in chiral three-dimensional mechanical metamaterials have been discussed in the context of micropolar Eringen continuum mechanics, which is a generalization of linear Cauchy elasticity. For cubic symmetry, Eringen elasticity comprises nine additional parameters with respect to linear Cauchy elasticity, of which three directly influence chiral effects. Here, we discuss the behavior of the static case of an alternative generalization of linear Cauchy elasticity, the Willis equations. We show that in the homogeneous static cubic case, only one additional parameter with respect to linear Cauchy elasticity results, which directly…

2018

We apply homogenization theory to calculate the effective electric conductivity and Hall coefficient tensor of passive three-dimensionally periodic metamaterials subject to a weak external static homogeneous magnetic field. We not only allow for variations of the conductivity and the Hall coefficient of the constituent material(s) within the metamaterial unit cells, but also for spatial variations of the magnetic permeability. We present four results. First, our findings are consistent with previous numerical calculations for finite-size structures as well as with recent experiments. This provides a sound theoretical justification for describing such metamaterials in terms of effective mate…

Role of dispersion on zero-average-index bandgaps

2009

We consider periodic multilayers combining ordinary positive index materials and dispersive metamaterials with negative index in some frequency ranges. These structures can exhibit photonic bandgaps which, in contrast with the usual Bragg gaps, are not based on interference mechanisms. Changing the dispersion models for the constituent metamaterial, we investigate its role in the production of zero-average-index bandgaps. In particular, we show the effect of each constitutive parameter on both bandgap edges. Finally, we give some approximated analytical expressions in terms of average parameters for the determination of the upper and lower limits of the zero-average refractive-index bandgap…