169,886 research outputs found
Increasing the absorption band of thin electromagnetic absorbers by using plasma resonance of wire medium
No full textDesign of nanostructured metamaterials in METACHEM
No full textIt is my pleasure to present the publication Nanostructured Metamaterials – Exchange between experts
in electromagnetics and material science.
Metamaterials are one of the new discoveries of the last decade. They present exceptional properties,
dominated by their geometrical structure and this publication will allow the reader to learn more about
these ‘artificial’ materials and about their interesting (and yet unexploited) potential applications. The design
and manufacturing of such materials has been made possible thanks to progress made in both materials
science and electrical engineering. With the help of bottom-up manufacturing techniques, a large number
of micrometer scale designs can now being scaled down to nanometer scale and therefore completely
new solutions can be investigated. The tools needed to create metamaterials include modelling, geometry
and property design, bottom-up manufacturing and structural and electron microscopy characterization
at the atomic- and nano-scale. By controlling the reactivity of atoms and molecules to create inclusions
and by controlling the positioning of these nano-inclusions, nanostructured metamaterials can been realised
with interesting fields of applications where waves are involved, such as ICT applications and noise reduction.
The 7th Framework Programme for Research (FP7), the European instrument for funding scientific research
and technological development up to 2013, is targeting synergy between traditional scientific disciplines
and this resulted in fostering four bottom-up manufacturing projects and a coordinated action on
characterisation of metamaterials. Their total budget is EUR 20M with a FP7 contribution of EUR 15M.
A workshop has been dedicated to metamaterials in December 2009 and its main outcome is presented
in this publication.
So often materials are the bottleneck or, positively, the enabler for technological progress resulting in
novel and sustainable products made available to all citizens. Within the larger family of industrial technologies,
material science and engineering show paramount potential to allow such progress with benefits for
industry and the society as a whole.
Metamaterials had a current market size of EUR 133 million in 2007 and are expected to grow to EUR 2.1 billion
in 2013 (1), a compound annual growth rate (CAGR) of 26.5 %. I hope that the interdisciplinary and creative
collaboration between material scientists and engineers together with ICT researchers will support this
growth by allowing secure understanding and rapid progress in the innovative field of metamaterials, as this
would allow exploiting their industrial (and later on, commercial) potential to the benefit of European
industrial growth and the creation of jobs.
Renzo Tomellini
European Commission
Head of Unit ‘Value-added Materials
Cross polarization of nano-objects located on a flat substrate in the presence of a glass microparticle
No full textIn this work, we theoretically show that the deep subwavelength objects located on a dielectric substrate under a glass microcylinder sufficiently close to its bottom point are strongly polarized in the direction that is radial with respect to the microcylinder. This is even in the case when the structure is illuminated by the normally incident light. Though the incident electric field in the area of the objects is polarized almost tangentially to the cylinder surface, a significant cross polarization arises in the object due to its near-field coupling with the cylinder. In accordance with our previous works, the radial polarization is the key prerequisite of the super-resolution granted by a glass microsphere. Extending our results to the 3D case, we claim that the same cross-polarization effect should hold for a glass microsphere. In other words, the reported study shows that the parasitic spread image created by the tangential polarization of the objects should not mask the subwavelength image created by the radial polarization.Peer reviewe
Inverse propagation method for evaluation of super-resolution granted by dielectric microparticles
No full textPublisher Copyright: © 2022 Optica Publishing GroupIn this work we report a theoretical study of the lateral resolution granted by a simple glass microcylinder. In this 2D study, we had in mind the 3D analogue—a microsphere whose ability to form a deeply subwavelength and strongly magnified image of submicrometer objects has been known since 2011. Conventionally, the microscope in which such an image is observed is tuned to see the areas behind the microsphere. This corresponds to the location of the virtual source formed by the microsphere at a distance longer than the distance of the real source to the miscroscope. Recently, we theoretically found a new scenario of super-resolution, when the virtual source is formed in the wave beam transmitted through the microsphere. However, in this work we concentrated on the case when the super-resolution is achieved in the impractical imaging system, in which the microscope objective lens is replaced by a microlens located at a distance smaller than the Rayleigh range. The present paper theoretically answers an important question: Which scenario of far-field nanoimaging by a microsphere grants the finest spatial resolution at very large distances? We found that the novel scenario (corresponding to higher refractive indices) promises further enhancement of the resolution.Peer reviewe
Simovski, “Dynamic model of artificial reactive impedance surfaces
No full textAbstract|New arti cial reactive impedance surfaces have been recently suggested by Sievenpiper et al. for antenna and waveguide applications. In particular, high impedance values corresponding to a magnetic wall can be realized in dense arrays of conducting patches over a conducting plane. In this paper, a dynamic model for the electromagnetic properties of such structures is developed. The analytical model takes into account electromagnetic interactions between all patches in in nite arrays excited by normally incident plane waves, as well as higher-order Floquet modes between the array and the ground plane. The results are compared with the known experiments
Equivalence of Angular Stability and Reflection Locality for Metasurfaces with Anomalous Reflection
No full textPublisher Copyright: © 2023 IEEE.The so-called generalized reflection law defines the fields reflected from non-uniform boundaries in terms of the local reflection coefficient. Absolute majority of researchers utilize the approximation of so-called reflection locality in which the reflection coefficient at a given point (at the reference unit cell position) is assumed to be the same as if the metasurface were uniform, i.e., all the unit cells surrounding the reference one were identical. It is known that this locally periodic approximation is adequate for anomalous reflectors in case of small deviations from the usual reflection law. In this talk we will present a proof that this approximation is adequate also for strongly anomalous reflections if (and only if) the reflection coefficient of the corresponding uniform metasurfaces is independent from the incidence angle.Peer reviewe
Advancing RIS Beamforming Efficiency: Moving Beyond Diagonal Matrix Techniques
No full text| openaire: EC/H2020/956256/EU//META WIRELESSOptimizing wireless propagation channels is essential for advancing future communication technologies, particularly in dynamic vehicular environments where high vehicle mobility is a challenge. This paper introduces a novel practical implementation of reconfigurable intelligent surfaces (RIS) that achieve highly efficient beamforming, significantly surpassing the limitations of the conventional diagonal phase shift approach. We expand the theoretical and optimization framework based on the discrete impedance model to accommodate practical design scenarios. We validate our approach by fabricating an RIS prototype and conducting experimental measurements using the parallel plate waveguide technique. The experimental results confirm the superior performance of our approach, demonstrating at least a 30% improvement in efficiency over diagonal matrix methods, thereby enhancing signal quality and coverage. This ensures seamless communication and ubiquitous connectivity, improving the quality of service by boosting the received signal.Peer reviewe
Experimental validation of the suppression of spatial dispersion in artificial plasma
No full textAn isotropic plasma is composed of free charge carriers. Wire medium is an artificial plasma that is constructed by aligning conducive wires in one-, two-, or three dimensions (see e.g. [1]). In the simplest form, that is the one-dimensional case, the wires are aligned in parallel with a certain lattice constant. In more complicated two- and three-dimensional wire media the wires are aligned in a similar way in parallel in two or three orthogonal directions, respectively. Unlike in the gas-like plasma, the electromagnetic properties of this artificial plasma are constrained by its geometrical structure. Such constrains are, for instance, anisotropy and spatial dispersion
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Revisiting substrate-induced bianisotropy in metasurfaces
No full textRecently, it has been shown that a metasurface of plasmonic nanospheres deposited on a highly refractive substrate requires a bianisotropic magnetoelectric coupling for its effective description. The effect has been coined substrate-induced bianisotropy. It leads to an asymmetric reflectance similar to bianisotropic metasurfaces. In this work, through a circuit model, we show that such bianisotropy does not necessarily emerge for all substrated metasurfaces. Indeed, we show that the thickness of the metasurface plays a crucial role to encounter substrate-induced bianisotropy. Moreover, by taking advantage of substrate-induced bianisotropy, we present the necessary conditions for the circuit model parameters to compensate the asymmetric reflectance generated by an intrinsically bianisotropic metasurface. We finally express that, in substrated metasurfaces, the asymmetric reflectance and the bianisotropic response are two separate issues albeit with interdependencies.Peer reviewe
- …
