Special Issue "Metamaterials"

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Hybrid and Composite Crystalline Materials".

Deadline for manuscript submissions: 30 June 2020.

Special Issue Editor

Prof. Paweł Szczepański
Website
Guest Editor
Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, Poland

Special Issue Information

Dear Colleagues,

Artificially engineered structures, known as metamaterials, offer distinctive electromagnetic properties and over the last few decades have been intensively investigated. Practical realization of these metamaterials has been enabled by rapidly developing material science and nanofabrication technologies. As such, they have been recognized as a milestone towards shaping electromagnetic response at will.

Over the last decade, the various types of metamaterials have created a vibrant research field centered on their high feasibility and applicability. The increasing amount of research related to metamaterials in recent years indicates a still growing and not fully explored potential. Possible tunability of metamaterial structures provides another degree of freedom for shaping performance characteristics of metamaterial-based devices, during both their design and operation.

The latest developments in the area of metamaterials encourage us to rethink our prior assumptions and question the paradigm that prevailed until now. In this vein, this Special Issue aims broadly to cover up-to-date aspects of theory, design, technology, and characterization related to hyperbolic metamaterials (HMMs) and other types of metamaterials as well as their current and future applications. We thus invite you to submit your work in those areas to the issue. We are especially interested in the following topics:

  • Effects of nonlocality
  • Waveguides and waveguiding systems
  • Spectral and spatial filtering
  • Beam and polarization steering
  • Super-Planckian thermal emission
  • Lasing, light amplification and absorption
  • Nonlinear effects
  • Sensing
  • Technology and characterization
  • Materials, design, and technology for tunable HMMs
Prof. Paweł Szczepański

Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (6 papers)

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Research

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Open AccessArticle
Narrow/Broad-Band Absorption Based on Water-Hybrid Metamaterial
Crystals 2020, 10(5), 415; https://doi.org/10.3390/cryst10050415 - 22 May 2020
Abstract
In this work, the possibility of a switchable metamaterial absorber is proposed to control absorption bandwidth in the WiMAX/LTE (worldwide interoperability for microwave access/long term evolution) band, by taking advantage of the low cost and myriad structural configurations afforded by water-based metamaterials. By [...] Read more.
In this work, the possibility of a switchable metamaterial absorber is proposed to control absorption bandwidth in the WiMAX/LTE (worldwide interoperability for microwave access/long term evolution) band, by taking advantage of the low cost and myriad structural configurations afforded by water-based metamaterials. By exploiting truncated cone-type resonators, the fractional bandwidth of 27.6% of absorption spectrum can be adjusted flexibly to be 7.4% of the narrow-band absorption depending on the volume of injected water, in both simulation and experiment at room temperature. In particular, this control method can be applied stably for different temperature of injected water. We describe a dynamic mechanism for broadband MA, as well as a principle for controlling the absorption characteristics utilizing a combination of magnetic resonance and perfect impedance matching. These results are a stepping-stone towards the realization of smart electronics integrated with multi-functional metamaterials in military, biomedical, communication and other fields. Full article
(This article belongs to the Special Issue Metamaterials)
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Open AccessArticle
Optimization of Ultra-Thin Pulsed-DC Magnetron Sputtered Aluminum Films for the Technology of Hyperbolic Metamaterials
Crystals 2020, 10(5), 384; https://doi.org/10.3390/cryst10050384 - 08 May 2020
Abstract
The future applications of hyperbolic metamaterials demand stacks of materials with alternative ultra-thin conductive/dielectric films with good homogeneity of the thickness and reduced roughness level. In this work, the technology of pulsed-DC magnetron sputtering of aluminum was optimized using the Taguchi method in [...] Read more.
The future applications of hyperbolic metamaterials demand stacks of materials with alternative ultra-thin conductive/dielectric films with good homogeneity of the thickness and reduced roughness level. In this work, the technology of pulsed-DC magnetron sputtering of aluminum was optimized using the Taguchi method in order to fabricate Al films with improved roughness level. The performed structural characterization proved the smaller Al domains and better homogeneity of the surface. The optimized process was used to fabricate a multilayer structure of Al/HfOx as the metamaterial media. The fabricated structures were optically characterized in the UV/VIS range. The presented findings demonstrated the tunability effect of the effective reflectance of the examined stacks. The presented results are promising for the future application of multilayer structures in novel photonic devices based on hyperbolic metamaterials. Full article
(This article belongs to the Special Issue Metamaterials)
Open AccessArticle
Reconfigurable Polarizer Based on Bulk Dirac Semimetal Metasurface
Crystals 2020, 10(3), 228; https://doi.org/10.3390/cryst10030228 - 21 Mar 2020
Abstract
In this paper, we propose a reflective polarizer in terahertz regime, which utilizes the Bulk-Dirac-Semimetal (BDS) metasurface can be dynamically tuned in broadband. The proposed polarizer is capable of converting the linear polarized wave into the circular polarized or the cross polarized waves [...] Read more.
In this paper, we propose a reflective polarizer in terahertz regime, which utilizes the Bulk-Dirac-Semimetal (BDS) metasurface can be dynamically tuned in broadband. The proposed polarizer is capable of converting the linear polarized wave into the circular polarized or the cross polarized waves by adjusting the Fermi energy (EF) of the BDS. In the frequency range of 0.51 THz and 1.06 THz, the incident linear polarized wave is converted into a circular polarized wave with an axial ratio (AR) less than 3 dB when EF = 30 meV. When EF = 45 meV, the cross-polarization conversion is achieved with the polarization conversion ratio (PCR) greater than 90% in the band of 0.57−1.12 THz. Meanwhile, the conversion efficiencies for both polarization conversions are in excess of 90%. Finally, the physical mechanism is revealed by the decomposition of two orthogonal components and the verification is presented by the interference theory. Full article
(This article belongs to the Special Issue Metamaterials)
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Open AccessArticle
Transmission Characteristics of Ultrasonic Longitudinal Wave Signals in Negative Refractive Index Materials
Crystals 2020, 10(3), 227; https://doi.org/10.3390/cryst10030227 - 21 Mar 2020
Abstract
Longitudinal waves have important applications in modern scientific research and production; as a special acoustic wave, longitudinal waves have a sound transmission performance in negative refractive index materials. This paper has designed a new structure for negative refractive index materials by virtue of [...] Read more.
Longitudinal waves have important applications in modern scientific research and production; as a special acoustic wave, longitudinal waves have a sound transmission performance in negative refractive index materials. This paper has designed a new structure for negative refractive index materials by virtue of COMSOL software and conducted related simulation analysis. Experimental results illustrated that the structure designed had good acoustic longitudinal wave transmission performance. Besides, the effect of sound wave focusing could be achieved by a combination of existing test methods. The design proposed could break the limitation of previous structures on acoustic longitudinal wave transmission. This study is expected to have important implications for the development of solid metamaterial structures. Full article
(This article belongs to the Special Issue Metamaterials)
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Open AccessArticle
Guided Optical Modes in Metal-Cladded Tunable Hyperbolic Metamaterial Slab Waveguides
Crystals 2020, 10(3), 176; https://doi.org/10.3390/cryst10030176 - 06 Mar 2020
Cited by 1
Abstract
We have theoretically investigated metal-cladded waveguides of tunable hyperbolic metamaterial (THMM) cores, employing graphene sheets as a tunable layer, in terms of guided waves propagation over near- to mid-infrared range, following the effective medium approximation. We have proven that these subwavelength guiding structures [...] Read more.
We have theoretically investigated metal-cladded waveguides of tunable hyperbolic metamaterial (THMM) cores, employing graphene sheets as a tunable layer, in terms of guided waves propagation over near- to mid-infrared range, following the effective medium approximation. We have proven that these subwavelength guiding structures offer a number of effects usually not found in other types of waveguides, including controllable propagation gap and number of modes, inversion of power flow direction with respect to phase velocity, TM mode propagation, and absence of the fundamental mode, which occur as a result of controlled change of the guiding layer dispersion regime. This is the first time that the above-mentioned effects are obtained with a single, voltage-controlled waveguiding structure comprising graphene sheets and a dielectric, although the presented methodology allows us to incorporate other tunable materials beyond graphene equally well. We believe that such or similar structures, feasible by means of current planar deposition techniques, will ultimately find their practical applications in optical signal processing, controlled phase matching, controlled coupling, signal modulation, or the enhancement of nonlinear effects. Full article
(This article belongs to the Special Issue Metamaterials)
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Review

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Open AccessReview
A Review of Acoustic Metamaterials and Phononic Crystals
Crystals 2020, 10(4), 305; https://doi.org/10.3390/cryst10040305 - 15 Apr 2020
Abstract
As a new kind of artificial material developed in recent decades, metamaterials exhibit novel performance and the promising application potentials in the field of practical engineering compared with the natural materials. Acoustic metamaterials and phononic crystals have some extraordinary physical properties, effective negative [...] Read more.
As a new kind of artificial material developed in recent decades, metamaterials exhibit novel performance and the promising application potentials in the field of practical engineering compared with the natural materials. Acoustic metamaterials and phononic crystals have some extraordinary physical properties, effective negative parameters, band gaps, negative refraction, etc., extending the acoustic properties of existing materials. The special physical properties have attracted the attention of researchers, and great progress has been made in engineering applications. This article summarizes the research on acoustic metamaterials and phononic crystals in recent decades, briefly introduces some representative studies, including equivalent acoustic parameters and extraordinary characteristics of metamaterials, explains acoustic metamaterial design methods, and summarizes the technical bottlenecks and application prospects. Full article
(This article belongs to the Special Issue Metamaterials)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Control wave propagation in metal-cladded HMM waveguides

Title: Exploiting nonlocality in anisotropic metamaterials

Title: Broadband omnidirectional near-infrared reflector based on one-dimensional photonic crystal containing hyperbolic metamaterials

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