Glide-Symmetric Metallic Structures with Elliptical Holes for Lens Compression
TL;DR: In this paper, the authors derived a mode-matching technique based on the generalized Floquet theorem for glide-symmetric structures, which benefits from a lower computational cost since it takes advantage of the glide symmetry in the structure.
Abstract: In this paper, we study the wave propagation in a metallic parallel-plate structure with glide-symmetric elliptical holes. To perform this study, we derived a mode-matching technique based on the generalized Floquet theorem for glide-symmetric structures. This mode-matching technique benefits from a lower computational cost since it takes advantage of the glide symmetry in the structure. It also provides physical insight on the specific properties of Floquet modes propagating in these specific structures. With our analysis, we demonstrate that glide-symmetric structures with periodic elliptical holes exhibit an anisotropic refractive index over a wide range of frequencies. The equivalent refractive index can be controlled by tuning the dimensions of the holes. Finally, by combining the anisotropy related to the elliptical holes and transformation optics, a Maxwell fish-eye lens with a 33.33% size compression is designed. This lens operates in a wideband frequency range from 2.5 GHz to 10 GHz.
Citations
More filters
TL;DR: In this article, an anisotropic unit cell based on glide symmetry is proposed for tailoring a metasurface that engineers an optically transformed Luneburg lens, which reduces the size of the lens by 25%.
Abstract: An anisotropic unit cell based on glide symmetry is proposed for tailoring a metasurface that engineers an optically transformed Luneburg lens. Thanks to the optical transformation, the size of the lens is reduced by 25%. The proposed lens is ultrawideband, and it covers multi-octave frequency bands. The required constitutive materials are achieved in an air gap bounded by top and bottom glide-symmetric metasurfaces; i.e., they are off-shifted by half the period. Each surface is implemented in standard printed-circuit-board technology, and its unit cell consists of a grounded substrate with an elliptical holey top cladding surrounded by metalized through-vias. This technology, known as substrate-integrated-holes (SIHs), mimics the operation of holes drilled in a parallel plate but provides the higher effective refractive index required for lens compression. The SIH is attractive for practical applications since most of the energy propagates in the air gap between the two surfaces and, therefore, it features low dielectric losses. Thanks to glide symmetry, the proposed metasurface demonstrates a further enhanced effective refractive index with lower dispersion over an ultra-wide bandwidth in comparison to its non-glide counterpart. A multimodal transfer-matrix approach is here employed to carry out the Bloch analysis of the proposed SIH.
23 citations
TL;DR: Focusing on the design of gap waveguide-based components, it is demonstrated that in practice it is often sufficient to use 1D glide symmetry, which is also simpler to mechanically realize, and if larger attenuation of lateral waves is needed, a diagonally directed 2D glide symmetric structure should be implemented.
Abstract: Recently, there has been an increased interest in exploring periodic structures with higher symmetry due to various possibilities of utilizing them in novel electromagnetic applications. The aim of this paper is to discuss design issues related to the implementation of holey glide-symmetric periodic structures in waveguide-based components. In particular, one can implement periodic structures with glide symmetry in one or two directions, which we differentiate as 1D and 2D glide symmetry, respectively. The key differences in the dispersion and bandgap properties of these two realizations are presented and design guidelines are indicated, with special care devoted to practical issues. Focusing on the design of gap waveguide-based components, we demonstrate using simulated and measured results that in practice it is often sufficient to use 1D glide symmetry, which is also simpler to mechanically realize, and if larger attenuation of lateral waves is needed, a diagonally directed 2D glide symmetric structure should be implemented. Finally, an analysis of realistic holes with conical endings is performed using a developed effective hole depth method, which combined with the presented analysis and results can serve as a valuable tool in the process of designing novel electrically-large waveguide-based components.
9 citations
TL;DR: In this article, a mode-matching formulation is presented and used to analyze the dispersion properties of twist-symmetric transmission lines, which are coaxial lines periodically loaded with infinitely thin screens, rotated with respect to each other to possess twist symmetry.
Abstract: A mode-matching formulation is presented and used to analyze the dispersion properties of twist-symmetric transmission lines. The structures are coaxial lines periodically loaded with infinitely thin screens, which are rotated with respect to each other to possess twist symmetry. The results obtained using the proposed formulation are in good agreement with those of commercial simulators. Furthermore, using the presented mode-matching formulation, it is demonstrated that the propagation characteristics in the twist-symmetric structures are linked to the scattering and coupling of the higher order modes. The physical insight offered by this analysis is valuable for the design of various electromagnetic devices, such as filters, antennas, and phase-shifters.
6 citations
TL;DR: A comprehensive overview of the past, present and future trends related to 3D metamaterial devices is presented in this paper , focusing on efficient computational methods, innovative designs and functional manufacturing techniques.
Abstract: Metamaterials are artificially engineered devices that go beyond the properties of conventional materials in nature. Metamaterials allow the creation of negative refractive indexes, light trapping with epsilon-near-zero compounds, bandgap selection, superconductivity phenomena, non-Hermitian responses and, more generally, to manipulate the propagation of electromagnetic and acoustic waves. In the past, low computational resources and the lack of proper manufacturing techniques have limited the attention to 1-D and 2-D metamaterials. However, the true potential of metamaterials will be ultimately reached in 3-D configurations, when the degrees of freedom associated to the propagating direction are finally exploited in design. This is expected to lead to a new era in metamaterial field, from which future high-speed and low-latency communication networks can benefit. Here, a comprehensive overview of the past, present and future trends related to 3-D metamaterial devices is presented, focusing on efficient computational methods, innovative designs and functional manufacturing techniques.
4 citations
TL;DR: In this article , the authors presented a new analytic homogenization technique for glide-symmetric holey parallel-plate waveguides (PPWs) and derived a closed-form expression of the effective refractive index, relying on the eigenmodes of the hole cross section.
Abstract: Glide-symmetric (G-S) waveguides made of metallic metasurfaces are a wideband, low-loss, low-cost, and conformable alternative to dielectric materials for the design of antenna lenses at millimeter waves. However, computing the effective refractive index of glide-symmetric waveguides with existing full-wave analysis techniques results in cumbersome parametric studies for each new design. This article presents a new analytic homogenization technique for glide-symmetric holey parallel-plate waveguides (PPWs). The dispersion equation of these structures, found by way of mode-matching, is simplified at low frequency using the properties of the modes resonating within the holes, independently of the hole shape. This simplified equation yields a closed-form expression of the effective refractive index, relying on the eigenmodes of the hole cross section. This formula avoids solving a 3-D full-wave problem and is fully analytic in the case of canonical hole shapes. Although derived in the quasi-static regime, it characterizes propagation over an ultrawide band, due to the low dispersive properties of glide symmetric structures. It is a function of the angle of propagation within the waveguide and can thus be used to study anisotropic properties. Its efficiency is demonstrated with the example of glide-symmetric PPWs with rectangular and circular holes.
3 citations
References
More filters
TL;DR: Metamaterials are typically engineered by arranging a set of small scatterers or apertures in a regular array throughout a region of space, thus obtaining some desirable bulk electromagnetic behavior as mentioned in this paper.
Abstract: Metamaterials are typically engineered by arranging a set of small scatterers or apertures in a regular array throughout a region of space, thus obtaining some desirable bulk electromagnetic behavior. The desired property is often one that is not normally found naturally (negative refractive index, near-zero index, etc.). Over the past ten years, metamaterials have moved from being simply a theoretical concept to a field with developed and marketed applications. Three-dimensional metamaterials can be extended by arranging electrically small scatterers or holes into a two-dimensional pattern at a surface or interface. This surface version of a metamaterial has been given the name metasurface (the term metafilm has also been employed for certain structures). For many applications, metasurfaces can be used in place of metamaterials. Metasurfaces have the advantage of taking up less physical space than do full three-dimensional metamaterial structures; consequently, metasurfaces offer the possibility of less-lossy structures. In this overview paper, we discuss the theoretical basis by which metasurfaces should be characterized, and discuss their various applications. We will see how metasurfaces are distinguished from conventional frequency-selective surfaces. Metasurfaces have a wide range of potential applications in electromagnetics (ranging from low microwave to optical frequencies), including: (1) controllable “smart” surfaces, (2) miniaturized cavity resonators, (3) novel wave-guiding structures, (4) angular-independent surfaces, (5) absorbers, (6) biomedical devices, (7) terahertz switches, and (8) fluid-tunable frequency-agile materials, to name only a few. In this review, we will see that the development in recent years of such materials and/or surfaces is bringing us closer to realizing the exciting speculations made over one hundred years ago by the work of Lamb, Schuster, and Pocklington, and later by Mandel'shtam and Veselago.
1,819 citations
TL;DR: This Review summarizes research on photonic, terahertz and microwave electromagnetic metamaterials and metadevices with functionalities attained through the exploitation of phase-change media, semiconductors, graphene, carbon nanotubes and liquid crystals.
Abstract: Metamaterials, artificial electromagnetic media that are structured on the subwavelength scale, were initially suggested for the negative-index 'superlens'. Later metamaterials became a paradigm for engineering electromagnetic space and controlling propagation of waves: the field of transformation optics was born. The research agenda is now shifting towards achieving tunable, switchable, nonlinear and sensing functionalities. It is therefore timely to discuss the emerging field of metadevices where we define the devices as having unique and useful functionalities that are realized by structuring of functional matter on the subwavelength scale. In this Review we summarize research on photonic, terahertz and microwave electromagnetic metamaterials and metadevices with functionalities attained through the exploitation of phase-change media, semiconductors, graphene, carbon nanotubes and liquid crystals. The Review also encompasses microelectromechanical metadevices, metadevices engaging the nonlinear and quantum response of superconductors, electrostatic and optomechanical forces and nonlinear metadevices incorporating lumped nonlinear components.
1,741 citations
02 Aug 2005
TL;DR: In this article, the authors proposed a planar guided-wave structure with double-negative (DNG) and single-negative (SNG) layers, and showed the properties of the planar guide-wave structures with DNG and SNG layers.
Abstract: Contributors. Preface. 1. Negative-Refractive-Index Transmission-Line Metamaterials (A. Iyer & G. Eleftheriades). 2. Passive Microwave Devices and Antennas Using Negative-Refractive-Index Transmission-Line Metamaterials (G. Eleftheriades). 3. Super Resolving Negative-Refractive-Index Transmission-Line Lenses (A. Grbic & G. Eleftheriades). 4. Gaussian Beam Interactions with DNG Metamaterials (R. Ziolkowski). 5. Negative Index Lenses (D. Schurig & D. Smith). 6. Planar Anisotropic Resonance-Cone Metamaterials (K. balmain & A. Luttgen). 7. Negative Refraction and Subwavelength Imaging in Photonic Crystals (C. Luo & J. Joannopoulos). 8. Plasmonic Nanowire Metamaterials (A. Sarychev & V. Shalaev). 9. An Overview of Salient Properties of Planar Guided-Wave Structures with Double-Negative (DNG) and Single-Negative (SNG) Layers (A Alu and N. Engheta). 10. Dispersion Engineering: The Use of Abnormal Velocities and Negative Index of Refraction to Control the Dispersive Effects (M. Mojahedi & G. Eleftheriades). Index.
1,050 citations
TL;DR: In this article, the existence of surface electromagnetic modes in corrugated surfaces of perfect conductors was explored and it was shown that these structures support surface bound states and that the dispersions of these modes have strong similarities with the dispersion of surface plasmon polariton bands of real metals.
Abstract: In this paper we explore the existence of surface electromagnetic modes in corrugated surfaces of perfect conductors. We analyse two cases: one-dimensional arrays of grooves and two-dimensional arrays of holes. In both cases we find that these structures support surface bound states and that the dispersions of these modes have strong similarities with the dispersion of the surface plasmon polariton bands of real metals. Importantly, the dispersion relation of these surface states is mainly dictated by the geometry of the grooves or holes and these results open the possibility of tailoring the properties of these modes by just tuning the geometrical parameters of the surface.
924 citations