Metamaterials and Metasurfaces—Historical Context, Recent Advances, and Future Directions
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2020-03-01 |
| Journal | IEEE Transactions on Antennas and Propagation |
| Authors | Ashwin K. Iyer, Andrea Alù, A. J. Epstein |
| Institutions | CUNY Advanced Science Research Center, Technion – Israel Institute of Technology |
| Citations | 110 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This document reviews the historical context, recent advances, and future directions of metamaterials and metasurfaces, focusing on their application in electromagnetics and antennas for an engineering audience.
- Core Value Proposition: Metamaterials (3D) and metasurfaces (2D) are artificial, engineered structures designed to exhibit electromagnetic properties (e.g., negative refractive index, zero permittivity) not found in natural materials, allowing unprecedented control over wave propagation.
- Historical Trajectory: The field evolved from early “artificial dielectrics” (1940s-1960s) used for lightweight RF components, to the theoretical prediction (Veselago, 1960s) and experimental realization (2001) of negative refractive index media using wire and split-ring resonator (SRR) arrays.
- Shift to Metasurfaces: Due to complex fabrication and high insertion losses in 3D metamaterials, research has increasingly focused on ultrathin 2D metasurfaces, which use gradient phase manipulation for efficient wavefront transformation (e.g., meta-lenses, reflect-arrays).
- Current Research Focus: Explosive growth across the LF to optical spectrum, emphasizing practical applications, miniaturization, and the integration of advanced computing (AI/Machine Learning).
- Future Directions (Breaking Limits): Key emerging trends include active, nonreciprocal, and time-modulated devices to break fundamental limitations of passive structures (e.g., bandwidth, reciprocity), and the exploration of nonlinear and topological metamaterials for enhanced robustness and exotic phenomena.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Historical Frequency Range | Millimeter-wave, Microwave | N/A | Early artificial chiral structures (Bose 1898, Lindman 1914) |
| Modern Frequency Range | LF to Optical | N/A | Full spectrum coverage of current research |
| Design Scale Requirement | Fractions (hundredths to tenths) | Wavelength (λ) | Required for effective macroscopic homogenization |
| Negative Index Demonstration | 2001 | Year | First experimental realization using wire/SRR arrays (Microwave) |
| Resolution Limit | Theoretically Infinite | N/A | Predicted capability of a negative-index flat lens (Superlens) |
| Metasurface Thickness | Ultrathin | N/A | Key advantage over 3D metamaterials for low insertion loss |
| Fabrication Scale | Nanometers or Angstroms | N/A | Required for infrared and visible light operation |
Key Methodologies
Section titled “Key Methodologies”- Artificial Dielectrics (Homogenization): Arranging metallic elements in 3D lattice structures to simulate the electromagnetic response of molecular lattices, achieving effective permittivity (ε) and permeability (µ) at long wavelengths.
- Subwavelength Scatterer Synthesis: Designing inclusions (e.g., split-ring resonators, wire arrays) to exhibit specific electric and magnetic responses that, when arrayed, result in exotic macroscopic properties like negative permeability or negative refractive index.
- Gradient Phase Manipulation: Utilizing 2D metasurfaces composed of engineered nanostructures to control the local amplitude and phase of an impinging wavefront, enabling functions like beam deflection and focusing (meta-lenses).
- Time-Modulation and Active Integration: Incorporating time-varying elements (e.g., diodes, active components) into metasurfaces to achieve nonreciprocal operation, frequency translation (serrodyne), and artificial Doppler effects.
- Transformation Electromagnetics (TE): Using coordinate transformations to design metamaterials that can alter optical space, enabling complex wave routing functions such as cloaking or focusing with holes/forbidden regions.
- Inverse Design and Synthesis: Employing algorithms based on surface-susceptibility representations to design planar and spherical metasurfaces with prescribed near-field or far-field scattering performance.
- Parity-Time (PT) Symmetry: Designing non-Hermitian systems with balanced gain and loss in geometrically asymmetric structures to achieve unusual responses, including negative refraction without the limitations of passive materials.
Commercial Applications
Section titled “Commercial Applications”- Telecommunications:
- 5G cellular networks and high-throughput communication.
- Planar phased arrays with extended scanning range.
- Massive MIMO performance enhancement using metasurface lenses.
- Ultracompact phase shifters and power dividers.
- Aerospace and Defense:
- Radar cross section (RCS) reduction for various antennas and dihedral corner reflectors.
- Space-borne lens antennas (collapsible 3D gradient-index lenses).
- Low-earth-orbit (LEO) satellite communication systems.
- Sensing, Imaging, and Measurement:
- Microwave imaging and computational imaging.
- Dielectric material characterization and defect detection.
- Multiband metamaterial absorbers for crowd estimation.
- Antenna Technology:
- Ultraminiaturized efficient antennas and Huygens dipole antennas.
- Leaky-wave antennas capable of dynamic beamforming and wideband operation.
- FSS-based vortex beam generators and pattern synthesis.
- Advanced Photonics and Optics:
- Nonlinear optics and frequency mixing at the subwavelength scale.
- Polarization-selective shielding and frequency-controllable polarization rotation (THz).
- Smart surfaces providing real-time reconfigurability for wavefront transformations.
- Fundamental Physics and Robust Systems:
- Topological metamaterials offering robustness to disorder and fabrication errors.
- Wireless power transfer.
- Nonreciprocal waveguiding and scattering control.
View Original Abstract
The trajectory of technological progress is ultimately guided by constraints at the physical level. In building a better device or system, we are bound 1) by the properties of the materials available to us and 2) by our understanding of physical phenomena. The physical laws of the universe, immutable as they are, lead us naturally to question whether we may be able to “engineer” raw materials to better allow us to achieve, control, and manipulate natural phenomena for useful purposes. In order to do this, we must first define what we mean by the term “material.” The perception that a material must appear homogeneous to the naked eye (i.e., “a uniform goop, with no discontinuous bits and pieces” <xref ref-type=“bibr” rid=“ref1” xmlns:mml=“http://www.w3.org/1998/Math/MathML” xmlns:xlink=“http://www.w3.org/1999/xlink”>[1]</xref> ), natural though it may be, is flawed: surely, all materials may be considered heterogeneous on some level of scale, but more importantly, this perspective is tied specifically to the electromagnetic response of these materials to wavelengths of light that are visible to the human eye. For example, although a diamond displays familiar macroscopic properties such as color, luster, and dispersion when viewed under visible light, illumination using X-rays results in a diffraction pattern that reveals its crystalline structure. Thus, the macroscopic properties of a material, e.g. polarizabilities, permittivity, permeability, refractive index, intrinsic bulk or surface impedance, and so on, are revealed only under illumination by wavelengths of light much longer than the size of its scatterers (i.e., its atoms and molecules) and their spacing (e.g., the lattice constants of a crystal). Therefore, it would seem that engineering such macroscopic properties of materials would require control of scattering at length scales of fractions—say several hundredths or even just tenths—of a wavelength, a prohibitive task if dealing in the nanometers or Angstroms. Fortunately, the reach of the electromagnetic spectrum permits us to examine the long-wavelength condition at frequencies where such length scales become much more accessible, such as the microwave and terahertz. Advances in nanoscale fabrication have extended this reach even further to infrared and visible light. At such scales, it becomes possible to synthesize scatterers to exhibit electric and magnetic responses that may then, in analogy to their natural counterparts, be homogenized to describe effective macroscopic electromagnetic properties apparent under illumination by correspondingly long wavelengths.
Tech Support
Section titled “Tech Support”Original Source
Section titled “Original Source”References
Section titled “References”- 2014 - Giant nonlinear response from plasmonic metasurfaces coupled to intersubband transitions [Crossref]
- 2018 - Active microwave cloaking using parity-time symmetric Satellites