Metamaterials最新文献

Metamaterials and photonic crystals are often distinguished by the requirement that the former have features fine compared with the wavelength, and thus be homogenizable. We discuss the assumption implicit in this: that the metamaterial microstructure have well defined effective dielectric constant and magnetic permeability (concentrating on the former case). We illustrate subtleties in the calculation of effective dielectric constant in the particular case of square prisms composed of dielectric arranged in a square array in a host medium of another dielectric constant, commenting on poles, zeros, essential singularities and branch cuts of the effective dielectric constant function.

Microwave absorption properties of a novel electromagnetic material – onion-like carbon (OLC) produced by annealing of detonation nanodiamonds in vacuum – have been studied in microwave frequency range. The OLC electromagnetic (EM) absorption ability can be optimized by varying the nanocarbon cluster size and nanodiamond annealing temperature so that effective EM coatings can be produced. Attenuation of EM waves in the 26–38 GHz frequency range had been studies for both OLC powder and polymer composites. For powder samples it was concluded that OLC aggregates with higher conductivity (higher annealing temperature of the precursor nanodiamond particles) and larger aggregate sizes provide higher efficiency for attenuation of the EM radiation. At the same time, when dispersed in a polymer matrix, more efficient shielding properties had been observed for OLC aggregates of the smallest sizes as compared to larger-sized aggregates at the same OLC loading. This is attributed due to the better dispersion and formation of a continuous conductive network by smaller aggregates (reaching the percolation threshold).

The 3D regular lattice of bi-spherical dielectric resonant inclusions arranged in a cubic lattice as two sets of dielectric spheres having different radii and embedded in a host dielectric material with lower dielectric permittivity was carefully investigated. The magnetic resonance mode in smaller spheres gives rise to the magnetic dipole momentum and the electric resonance mode in bigger spheres is responsible for the electric dipole momentum. The magnetic resonance corresponding to the first Mie resonance in the spherical particles is followed by forming a regular array of effective magnetic dipoles, and the structure of the identical spherical dielectric resonators can be designed as an isotropic μ-negative 3D-metamaterial. At the same time, it was found experimentally and by the simulation that the resonant response of the electric dipole was weakly pronounced and the ɛ-negative behavior was remarkably suppressed. To enhance the electric dipole contribution, two different ways were considered: (i) using another kind of symmetry of the bi-spherical arrangement of the particles corresponding to the body-centered cubic symmetry instead of the symmetry of NaCl analog considered previously; (ii) using a strong coupling between the identical resonant dielectric spheres arranged in the simple cubic symmetry for creation of the structure exhibiting properties of the isotropic DNG medium.

Here, we develop a nonlocal homogenization model to characterize the electrodynamics of an array of cubic particles made of resonant rings. The effective parameters are calculated from the microscopic fields produced by a periodic external excitation. It is confirmed that the spatial dispersion effects cannot be neglected in the regime where μ ≈ 0. We demonstrate that when the array of resonant rings is combined with a triple wire medium formed by connected wires, the structure may behave approximately as an isotropic left-handed material.

We have experimentally realized a method of images construction in atom optics, based on the idea of optical pinhole camera. Generation of identical images with maximum resolution has been explored. With the use of an atom pinhole camera we have built on a Si and glass surfaces an array of identical arbitrary-shape atomic nanostructures with the minimum size of an individual nanostructure’s element down to 50 nm. Limitations of the approach for fabrication of metamaterials are discovered.

The frequency-scanning capabilities of continuous-type leaky-wave antennas have usually been restricted to main-beam pointing angles within the forward quadrant. With the appearance of metamaterial concepts, wave propagation with negative and zero phase constant has made it possible to spread the scanning directions, allowing main-beam angles into the backward quadrant, as well as the broadside direction. In this paper, a straight long slot antenna, implemented in a rectangular waveguide with dielectric-filled corrugations, is analyzed, constructed and measured, and an analysis method, based on an equivalent homogeneized waveguide, is proposed. Some features of the antenna, such as losses, radiation pattern and gain are studied, in order to assess the performance and suitability of the composite right/left-handed waveguide technology used. The obtained results highlight the limiting factors for the applicability of the corrugated waveguide in antenna applications, while confirm the validity of the analysis technique proposed.

This publication presents the design, microfabrication and characterization of microwave artificial dielectric for highly compact circuits. The investigated artificial dielectric is integrated thanks to microtechnology using plastic-based materials. Two comprehensive modelling approaches and design methodology are presented and experimentally validated. We then demonstrate that artificial dielectrics permit the elaboration of miniaturized microwave circuits as well as potential mechanical bending ability.