Broadband visible metamaterial absorber based on a three-dimensional structure

In this paper, a broadband metamaterial absorber is successfully designed by a three-dimensional structure. And the three-dimensional absorber is just obtained by a two-dimensional structure which rotates 90°along x-axis. The simulated results show that the absorption of the three-dimensional metamaterial absorber is much better than the two-dimensional absorber. Moreover, the absorber is polarization-sensitive for the incident electromagnetic waves due to the asymmetry of the structure. Compared with the Y-polarization wave, the proposed absorber can realize broadband absorption with greater than 90% from 355.6 to 737.7 THz for X-polarized wave. Finally, based on the analysis of the electric field and surface current distributions, it can demonstrate that the localized surface plasmons and dipoles resonances will play an important role in the broadband absorption. And we believe that the metamaterial absorber will have many potential applications in emitter and energy harvesting.     

Multi-band microwave metamaterial absorber based on coplanar Jerusalem crossesMulti-band microwave metamaterial absorber based on coplanar Jerusalem crosses

The influence of the gap on the absorption performance of the conventional split ring resonator （SRR） absorber is investigated at microwave frequencies. Our simulated results reveal that the geometry of the square SRR can be equivalent to a Jerusalem cross （JC） resonator and its corresponding metamaterial absorber （MA） is changed to a JC absorber. The JC MA exhibits an experimental absorption peak of 99.1% at 8.72 GHz, which shows an excellent agreement with our simulated results. By simply assembling several JCs with slightly different geometric parameters next to each other into a unit cell, a perfect multi-band absorption can be effectively obtained. The experimental results show that the MA has four distinct and strong absorption peaks at 8.32 GHz, 9.8 GHz, 11.52 GHz and 13.24 GHz. Finally, the multi-reflection interference theory is introduced to interpret the absorption mechanism.     

Optical metamaterial absorber based on leaf-shaped cells

We present the model of an infrared metamaterial absorber composed of metallic leaf-shaped cells, dielectric substrate, and continuous metallic film. Numerical simulation confirms an absorptivity of 99.3% at the infrared frequency of 126.7 THz with this metamaterial model. The proposed metamaterial absorber could be fabricated with an electrochemical deposition technique. Our simulated results show the absorption feature of this metamaterial absorber could be well manipulated with different incident angles and radiation modes. The optical metamaterial absorber proposed in this paper has potential applications such as infrared imaging devices, thermal bolometers, wavelength-selective radiators, and optical bistable switches.     

Triple-band metamaterial absorber based on single resonator

The single resonator generally reveals a single absorption band, and the resonators with different sizes or shapes have to be arranged in order to achieve multi-absorption bands. We propose the triple-band metamaterial absorber by utilizing only single resonator. Meta-atoms are made of the toothed-wheel shape metallic pattern and a continuous metallic plane, separated by a dielectric layer. The first and the third absorption bands are induced by the fundamental and the third-harmonic magnetic resonances, respectively, and the second absorption band is induced by the magnetic resonance relevant to two grooves. In addition, the diffraction peak appears between the second and the third absorption bands, due to the surface currents which are separated between the upper and the lower metallic pattern parts. The proposed structure is scalable to smaller size for the infrared and the visible regimes.     

Wideband omnidirectional infrared absorber with a patchwork of plasmonic nanoantennas

In this Letter, we demonstrate experimentally that a patchwork of four metal-insulator-metal patches leads to an unpolarized wideband omnidirectional infrared absorption. Our structure absorbs 70% of the incident light on a 2.5 μm bandwidth at 8.5 μm. It paves the way to the design of wideband efficient plasmonic absorbers in the infrared spectrum.     

Perfect metamaterial absorber based on a split-ring-cross resonator

In this paper, we present a polarization-insensitive metamaterial (MM) absorber which is composed of the dielectric substrate sandwiched with split-ring-cross resonator (SRCR) and continuous metal film. The MM absorber is not limited by the quarter-wavelength thickness and can achieve near-unity absorbance by properly assembling the sandwiched structure. Microwave experiments demonstrate the maximum absorptivity to be about 99% around 10.91 GHz for incident wave with different polarizations. The surface currents distributions of the resonance structure are discussed to look into the resonance mechanism. Importantly, our absorber is only 0.4 mm thick, and numerical simulations confirm that the MM absorber could achieve very high absorptivity at wide angles of incidence for both transverse electric (TE) wave and transverse magnetic (TM) wave. The sandwiched structure is also suitable for designing of a THz and even higher frequency MM absorber, and simulations demonstrate the absorption of 99% at 1.105 THz.     

Plasmonic electromagnetically-induced transparency in metamaterial based on second-order plasmonic resonance

Using only two gold strips, we propose a scheme for generation of the plasmonic analogue of electromagnetically-induced transparency (EIT) in stacked optical metamaterials by utilizing the second-order plasmon resonance. In addition, we show that the plasmonic EIT can be achieved with asymmetric structure, since the asymmetric structure allows the excitation of the dark mode.     

Perfect metamaterial absorber

We present the design for an absorbing metamaterial (MM) with near unity absorbance A(omega). Our structure consists of two MM resonators that couple separately to electric and magnetic fields so as to absorb all incident radiation within a single unit cell layer. We fabricate, characterize, and analyze a MM absorber with a slightly lower predicted A(omega) of 96%. Unlike conventional absorbers, our MM consists solely of metallic elements. The substrate can therefore be optimized for other parameters of interest. We experimentally demonstrate a peak A(omega) greater than 88% at 11.5 GHz.     

Broad band absorber based on cascaded metamaterial layers including graphene

In order to extend the absorption band of the metamaterial with tilted graphene sheets, we use cascaded metamaterial layers and study the dependence of absorption on the structure parameters. The absorption spectra can be obtained through the transfer matrix method that we derive from the special metamaterial. The individual band of these metamaterial layers could be adjusted by modifying their geometrical and electrical parameters. We find that the absorption bandwidth of cascaded structure can be much increased with the number of layers increasing.     

Realisation of a humidity sensor based on perfect metamaterial absorber

In this paper, we have proposed and investigated a humidity sensor based on perfect metamaterial absorber. The sensor is composed of three layers, which are metallic particle array on the top, porous silicon in the middle layer and metallic film at the bottom. According to the effective medium approximation, the effective permittivity of porous silicon is mainly determined by the filling fraction of water condensation. It is shown that the resonant wavelength displays significant red-shift with the increasing effective permittivity of porous silicon. Furthermore, the simulation results indicate that the refractive index sensitivity of absorber is high to 249 nm/RIU, which makes our structure be an ideal candidate for evaluating the humidity of environment.     

Ultra-thin broadband metamaterial absorber

The design, fabrication, and measurements of a broadband metamaterial absorber are reported. The proposed metamaterial absorber consists of circular metallic patches and a metallic ground plane separated by a dielectric layer. Increasing the number of metallic patches can broaden the frequency range when their resonances are closely packed together, thereby resulting in a broadband resonance. Experimental results show that the proposed absorber has high absorptivity, with a full width at half maximum absorption bandwidth of 2.8 GHz and the relative FWHM absorption bandwidth of 25.3?%. In addition, the absorber can operate at a wide range of incident angles under both transverse electric and transverse magnetic polarizations.     

Perfect-absorber metamaterial based on flower-shaped structure

We theoretically and experimetally investigated the narrow-band peak of perfect absorber (PA), which was realized with a metal–dielectric–metal scheme based on a flower-shaped structure (FSS). The PA slabs were designed and fabricated to work in the GHz range of electromagnetic radiation. The absorption is due to the magnetic influence and therefore, the resonance frequency can be easily controlled without affecting the efficiency of the absorption peak by changing the dimensional parameters of the FSS. In addition, the FSS also results in polarization independence of electromagnetic waves, as expected due to its geometry.     

Ultracompact and dynamically tunable plasmonic THz switch based on graphene microcavity metamaterial

Optical Review - We propose and discuss a compact and tunable plasmonic terahertz (THz) metamaterial switch based on graphene microcavity. Due to the joint effect of graphene plasmon resonances and...     

Magnetic medium broadband metamaterial absorber based on the coupling resonance mechanism

In this paper, we present a design, simulation and experimental measurement of a metamaterial absorber (MMA) in the microwave regime. The proposed MMA structure consists of periodic cross electric resonators separated from the ground metal plane using a magnetic composite layer. The broadband absorption can be ascribed to the periodic cross electric resonators. The anti-parallel currents are observed at the peak frequency on the surface of the MMA and the ground metal plane, respectively, and thus the coupled resonance magnetic field occurs in the magnetic medium resulting in the magnetic loss. The new absorption peak located at 2.8 GHz broadens the whole absorption spectrum. The frequency of this peck is lower than that of the cross resonator of 3.7 GHz, suggesting the distinguish resonance mechanism: the absorbing properties are ascribed to the phase cancellation, Ohmic loss, dielectric loss at the end of the cross pattern, and the magnetic loss caused by the above mentioned coupled magnetic field. The obvious absorption peak at 2.8 GHz is also observed experimentally verifying the simulation result. All these results indicate the proposed MMA structure is promising for microwave absorbing application.     

Single-/dual-band metamaterial absorber based on cross-circular-loop resonator with shorted stubs

A single-/dual-band metamaterial absorber (MMA) based on cross-circular-loop resonator (CCLR) with shorted stubs is discussed at microwave frequencies in this paper. The single-/dual-band characteristics are realized by adjusting the positions of the shorted stubs. We briefly analyze the equivalent circuit model of the MMA unit cell and then numerically and experimentally investigate the near-perfect absorptions in such two conditions (single- and dual-band). The results indicate that the proposed MMA exhibits near-perfect impedance matching with free space and high absorptivity of 99.74?% at 8.65?GHz for single-band condition, and absorptivities of 99.75?% and 97.35?% at 8.525 and 9.1?GHz, respectively, for dual-band condition. It also exhibits a wide range of angles of incidence for both transverse electric (TE) and transverse magnetic (TM) radiation. The two operating frequency bands, in dual-band condition, can be further controlled by adjusting the positions of shorted stubs or adding other shorted stubs. So it opens the way to fabricate controllable MMAs, and so controllable perfectly matched layers and bolometers.     

基于二氧化钒宽、窄带可切换的双功能超材料吸收器研究

本文提出了一种宽、窄带可切换的双功能超材料吸收器.在超材料吸收器的结构中,引入了相变材料二氧化钒(VO2),仅利用单个可切换超表面就能实现不同的功能,其不同功能之间的相互转换通过VO2绝缘态和金属态之间的可逆相变特性实现.当VO2处于金属态时,设计的结构可以看作一个超材料宽带吸收器.仿真结果表明,在1.55THz至2....