A wide-angle and polarization-insensitive tunable metamaterial absorber based on graphene

A metamaterial perfect absorber (MPA) using elliptical silver nanoparticles is proposed and investigated to provide 100% absorption for both transverse electric and transverse magnetic polarizations with a wide range of incident angles and polarization independence. Metamaterial absorbers with narrow absorption performance over a wide frequency range are significantly desired in sensing applications. Incident angle insensitivity and polarization angle independence are key features of MPAs. The output characteristics are examined using the three-dimensional finite difference time domain method. The effective medium theory and transmission line theory are applied to investigate the simulation results. Here, the 100% absorption occurs at resonance wavelength of λres = 2290 nm, and maximum sensitivity and figure of merit become 200 nm/RIU and 720 RIU-1, respectively. The results show that an absorption spectrum is insensitive to the incident angle of 0°-60°. The proposed device can be used as a high-performance biosensor and photodetector.

In this paper, a dual-band perfect metamaterial absorber based on graphene is proposed in the terahertz region. The metamaterial absorber consists of two sizes of graphene disks and a gold film separated by a dielectric spacer in a unit cell. The numerical results demonstrate that the dual-band perfect absorption can be achieved by the superposition of the specific absorption peaks induced by different disks. The resonance frequency can be tuned via controlling the graphene conductivity and the sizes of the disks. The metamaterial absorber can achieve selectively frequency tunability and it can tune each resonance independently. And the dual-band absorption will not be changed when the small disks move along the diagonal within the range of our research. In addition, owing to the symmetry of the structure, the absorber is insensitive to polarization and can keep a high absorptivity with a wide angle. The flexible and simple design makes it possible for our proposed single-layer graphene absorber to be applied in many metamaterial fields, such as sensing, detecting, and cloaking objects.

Optically tunable metamaterial perfect absorber on highly flexible substrate

We present the design, characterization, theoretical and experimental verification of a tunable perfect metamaterial absorber (MA) based electromagnetic (EM) energy harvesting and sensor application. We have used the golden ratio while determining the dimensions allowing a simple configuration and an easy fabrication for the proposed structure. We have examined and analyzed the perfect absorption (both numerically and experimentally) and EM energy harvesting (numerically) behaviors of the proposed structure in order to verify and show the characteristics of the model. It is shown that 99.9 % maximum absorption rate is achieved at 6.78 GHz, and MA structure can be used as an EM energy collector. In order to support the numerical study, an experimental study is realized. We have then developed a sensor application of the proposed MA structure and observed the effects of the harvesting system. Perfect MA sensor based EM energy harvesting system is successfully achieved.

In this paper, a tunable terahertz metamaterial absorber is proposed, and the resonant frequency can be controlled by the variation of temperature and the permittivity. For the top layer of the absorber, which consist of a split ring resonator (SRR), and substrate strontium titanate dielectric layer was filled into the two slits of the SRR. The simulated results show that the absorber has a distinct absorption peak at f = 1.26 THz for T = 300 K, which is close to the calculated resonant frequency fm ≈ 1.268 THz, and the absorptivity can achieve 99.93%. To explain the physical mechanism of the absorption, the relative impedance, the surface current and equivalent LC-circuit are analyzed, which could further demonstrate that the magnetic resonant play a major role for the absorption. Moreover, the resonant point will produce a blue-shift with the increase of the temperature, and a red-shift will be appeared with the varying of the permittivity, so that the tunable metamaterial absorber has an application in sensing.

An tunable ultra-wideband metamaterial absorber (MMA) in the THz regions based on the phase transition of VO2 film was presented in this paper. Firstly, we simulated the absorption of MMA at different temperature, the results showed that the absorption was up to 90% from 5.464THz to 10THz with the bandwidth of 4.536THz when the temperature was 60°C and altering the designed MMA ’ s temperature can realize its amplitude tunable property. Secondly, its physical mechanism of electromagnetic absorption and amplitude adjustment were explored by monitoring the surface current and electric field. We proved that the MMA was insensitive to the polarization, incident angle and thickness of VO2 film at last.

Recently, metamaterial absorber has attracted considerable attention because of a broad range potential application to electromagnetic stealth, electromagnetic detectors, and electromagnetic communication. And to solve the problem which traditional metamaterial absorbers can only operate at a fixed frequency or within a limited frequency range, the tunable metamaterial absorbers attract more and more attention. But the previous metamaterial absorber can only achieve adjustable absorption in a single frequency band, which has not met people’s increasingly higher requirements for practical applications. To solve this problem, a multispectral tunable metamaterial absorber was designed by combining VO2 and metamaterial absorbers using the phase transition characteristics. In this paper, the absorption rate curve in the terahertz band and infrared band had been simulated by CST Microwave Studio software. And the simulation results showed that the metamaterial exhibited meta-absorption in the terahertz band when the temperature was set to high temperature (80°C) and the VO2 behaved as a metal phase in this temperature. However, the simulation results showed that the metamaterial exhibited meta-absorption in the infrared band when the temperature was set to low temperature (40°C) and the VO2 behaved as an insulator phase. Furthermore, the absorptive properties of the metamaterial absorber had been simulated under different lengths of VO2-cross when the VO2 behaved as a metal phase and under different lengths of metal-cross when the VO2 behaved as an insulator phase. Finally, the mechanism of electromagnetic absorption and multispectral tunable were discussion by simulating and analyzing the surface current distribution and electric field of the metamaterial absorber. The results showed that the metamaterial absorber can realize meta-absorption in the terahertz band or infrared band by changing the temperature which have potential application values in the fields of multispectral stealth, multispectral detection and multispectral communication.

Numerical investigation of a tunable metamaterial perfect absorber consisting of two-intersecting graphene nanoring arrays

Tunable quad-band perfect metamaterial absorber on the basis of monolayer graphene pattern and its sensing application

An X-shaped triple split ring resonator-based metamaterial perfect absorber with quad-band incident and polarization angle insensitivity for C, X, and Ku band applications

Tunable graphene-based metamaterial thermal absorber design for thermal sensing applications with behaviour prediction using machine learning

We theoretically present a concise and tunable dual-band metamaterial absorber composed of a typical metal-dielectric-metal structure in the terahertz regime. The dual-band absorption originates from two different resonance modes induced in one square ring, which is different from the common dual-band absorber composed of a super unit with several different-sized structures. The proposed absorber can realize dynamic tunability through changing the permittivity of the dielectric layer by applying different temperatures. Other good performances, such as a wide incident angle and polarization insensitivity, are also available for the proposed absorber. Such a metamaterial absorber is a promising candidate for terahertz imaging and detection.

Metamaterial absorbers display potential applications in the field of photonics and have been investigated extensively during the last decade. We propose a dual-band resonant metamaterial absorber with right-angle shaped elements (RAEs) in the terahertz range based on numerical simulations. The absorber remains insensitive to a wide range of incidence angles (0°–70°) by showing a minimum absorbance of ~80% at 70°. Furthermore, the proposed absorber is highly independent on any state of polarization of the incidence electromagnetic wave due to the high absorbance, i.e., greater than 80%, recorded for the considered polarization states. To further comprehend the slight variations in absorbance as a function of change in the angle of incidence, the impedance of the structure has been critically examined. The metamaterial absorber is simple in design, and we provide a possible path of fabrication.

Wide-band polarization independent perfect metamaterial absorber based on concentric rings topology for solar cells application

A broadband polarization-independent perfect absorber with tapered cylinder structures