The advent of negative index materials has spawned extensive research into metamaterials over the past decade. Metamaterials are attractive not only for their exotic electromagnetic properties, but also their promise for applications. A particular branch–the metamaterial perfect absorber (MPA)–has garnered interest due to the fact that it can achieve unity absorptivity of electromagnetic waves. Since its first experimental demonstration in 2008, the MPA has progressed significantly with designs shown across the electromagnetic spectrum, from microwave to optical. In this Progress Report we give an overview of the field and discuss a selection of examples and related applications. The ability of the MPA to exhibit extreme performance flexibility will be discussed and the theory underlying their operation and limitations will be established. Insight is given into what we can expect from this rapidly expanding field and future challenges will be addressed.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/adma.201200674

Metamaterial Electromagnetic Wave Absorbers

A microwave ultra-broadband polarization-independent metamaterial absorber is demonstrated. It is composed of a periodic array of metal-dielectric multilayered quadrangular frustum pyramids. These pyramids possess resonant absorption modes at multi-frequencies, of which the overlapping leads to the total absorption of the incident wave over an ultra-wide spectral band. The experimental absorption at normal incidence is above 90% in the frequency range of 7.8-14.7GHz, and the absorption is kept large when the incident angle is smaller than 60 degrees. The experimental results agree well with the numerical simulation.

Ultra-broadband Microwave Metamaterial Absorber

A microwave ultra-broadband polarization-independent metamaterial absorber is demonstrated. It is composed of a periodic array of metal-dielectric multilayered quadrangular frustum pyramids. These pyramids possess resonant absorption modes at multi-frequencies, of which the overlapping leads to the total absorption of the incident wave over an ultra-wide spectral band. The experimental absorption at normal incidence is above 90% in the frequency range of 7.8–14.7 GHz, and the absorption is kept large when the incident angle is smaller than 60°. The experimental results agree well with the numerical simulation.

Ultra-broadband microwave metamaterial absorber

A high-temperature stable broadband plasmonic absorber is designed, fabricated, and optically characterized. A broadband absorber with an average high absorption of 95% and a total thickness of 240 nm is fabricated, using a refractory plasmonic material, titanium nitride. This absorber integrates both the plasmonic resonances and the dielectric-like loss. It opens a path for the interesting applications such as solar thermophotovoltaics and optical circuits.

Refractory plasmonics with titanium nitride: broadband metamaterial absorber.

Electromagnetic absorbers have drawn increasing attention in many areas. A series of plasmonic and metamaterial structures can work as efficient narrowband absorbers due to the excitation of plasmonic or photonic resonances, providing a great potential for applications in designing selective thermal emitters, biosensing, etc. In other applications such as solar-energy harvesting and photonic detection, the bandwidth of light absorbers is required to be quite broad. Under such a background, a variety of mechanisms of broadband/multiband absorption have been proposed, such as mixing multiple resonances together, exciting phase resonances, slowing down light by anisotropic metamaterials, employing high loss materials and so on.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/lpor.201400026

Plasmonic and metamaterial structures as electromagnetic absorbers

The design and realization of a multi-band and polariza- tion insensitive metamaterial absorber is presented. The structure with thickness 1.1mm consists of six close rings which distribute in two metallic layers separated by FR4 flber glass PCB substrates. Ex- perimental results show that over 93.3% absorption can be achieved in this metamaterial absorber at multiple frequency bands (more than two). Due to the rotational symmetric pattern of the metamaterial, the performance of the absorber is insensitive to the polarization of the incident waves, indicating the superiority of the structure in the application.

/pdf/multi-band-and-polarization-insensitive-metamaterial-5z0umvcq14.pdf

Multi-band and polarization insensitive metamaterial absorber

The magnetic properties of the metamaterial composed of both periodic and aperiodic closed rings are studied. Experimental results validate that metamaterials with 0 < " < 1 can be non- dispersive in a wide frequency range. The magnetic properties are insensitive to disorders of the closed rings, e.g., the position disorders and the size disorders. The related causality issue is also discussed.

/pdf/magnetic-properties-of-metamaterial-composed-of-closed-rings-2bxm95t8nv.pdf

Magnetic Properties of Metamaterial Composed of Closed Rings

The permittivity of extra thin silk cloth is usually measured through some complex methods in the past. Here we propose a convenient and ∞exible method to measure the permittivity of extra thin silk cloth using resonant metamaterial structures. The metamaterial structures used here are symmetric split ring resonators (SRRs). The principle is that the resonant frequency of the SRRs is very sensitive to the permittivity of the surrounding medium. Therefore, the relative permittivity of an extra thin medium as silk cloth can be determined. Our experimental measurement shows that the relative permittivity of the silk cloth is 4.5. A piece of printing paper is also measured with a relative permeability of 1.4. The efiectiveness of the method in determining the permittivity of a solid medium is very useful in future applications.

/pdf/experimental-measurement-method-to-determine-the-4rljm0htiu.pdf

Liang Huang

Papers

Multi-band and polarization insensitive metamaterial absorber

Magnetic Properties of Metamaterial Composed of Closed Rings

Experimental Measurement Method to Determine the Permittivity of Extra Thin Materials Using Resonant Metamaterials