Broadband Perfect Absorption Research Articles

Working Mechanism and Progress of Electromagnetic Metamaterial Perfect Absorber

Electromagnetic metamaterials are artificial subwavelength composites with periodic structures, which can interact strongly with the incident light to achieve effective control of the light field. Metamaterial absorbers can achieve nearly 100% perfect absorption of incident light at a specific frequency, so they are widely used in sensors, optical switches, communication, and other fields. Based on the development history of metamaterials, this paper discusses the research background and significance of metamaterial perfect absorbers. Some perfect absorption mechanisms, such as impedance matching and coherent perfect absorption, are discussed. According to the functional division, the narrowband, dual frequency, multi-frequency, broadband, and tunable metamaterial perfect absorbers are briefly described.

Colloidal self-assembly based ultrathin metasurface for perfect absorption across the entire visible spectrum

Abstract Perfect absorption over the entire visible spectrum can create a dark background for acquiring images with high contrast and improved resolution, which is crucial for various applications such as medical imaging, biological detection, and industrial non-destructive testing. The broadband absorption is desired to be achieved in an ultrathin structure for low noise as well as high integration. Here, we experimentally demonstrate a metasurface broadband perfect absorber with an ultrathin thickness of 148 nm and a large area of ∼10 cm2. Such a metasurface, with more than 97% absorption in the wavelength range from 400 to 800 nm, is composed of chromium nanodisk hexagonal array deposited on a chromium substrate with a silica spacer. A self-assembly based colloidal lithography nanofabrication method is developed for the scalable fabrication of the proposed nanostructure. We attribute the broadband absorption to the spectrally overlapped Fabry–Perot resonance, surface plasmon polariton, and localized surface plasmon resonances. Our results offer a novel approach to wafer-scale and low-cost manufacturing of absorption-based devices for applications such as high-contrast imaging and optical modulation.

Superimposed multilayer randomly distributed graphene quantum dots and broadband terahertz perfect absorber

For investigating broadband perfect absorption in the Terahertz region, a multilayer structure using superimposed Graphene quantum dots with Gaussian distribution radius is proposed. At first, a three-layer metamaterial structure, which is composed of graphene quantum dots at the top layer, dielectric material at the middle layer, and finally gold layer at the bottom is considered and investigated. The radius Gaussian distribution for three radii 400, 450, and 500 nm is considered. Results for the proposed structure including 3, 5, and 7 layers are extracted and compared. Simulation results for the 7-layer case show a broadband absorption range of (4.2 to 8.1 THz), and (4.3 to 8.71 THz) absorption value above 70%. The dielectric material is Si3N4 in the proposed structure.

Broadband perfect optical absorption enabled by quasi-bound states in the continuum in graphene non-concentric rings.

Graphene plasmons, possessing a lot of unique optical properties, have been employed to enable a variety of applications in the THz frequency range. Here, we demonstrate bound states in the continuum (BICs), electromagnetically induced transparency (EIT)-like effects, high-performance broadband optical absorption (OA), and narrow-band OA in a square lattice of graphene non-concentric rings (GNCRs). We show that due to inversion symmetry breaking, the symmetry-protected BICs will evolve into quasi-BICs as the eccentricity of GNCRs becomes nonzero, manifested itself as a new resonance dip appearing in the transmission spectrum. The observation can be well described by a coupled-oscillator model, namely, the coupling between a dipole state and a quadrupole state. Besides, as the eccentricity becomes very large, the structure can also support EIT-like effects, in which a transparency window will occur at the frequency of the original transmission dip caused by the dipole state, and the transmission spectrum turns into a typical W-shape. Based on the idea of BICs, we propose a broadband terahertz (THz) perfect OA by using the typical sandwiched structure, namely, with the configuration of the GNCR layer-spacer layer-metal layer. Full wave simulations are performed, which show that the OA of over 90% absorptance can be achieved at frequencies from 0.67 THz to 1.66 THz, and over 99% absorptance can be achieved at frequencies from 1.24 THz to 1.49 THz. In the absorption band, three peaks come from three graphene plasmonic modes, which are two dipole resonances and a quadrupole resonance induced by symmetry breaking. Moreover, the perfect OA performance can be well maintained for oblique incidences of transverse electric polarization, with an incidence angle of up to 30°. Finally, we show that the broadband perfect OA can be switched to narrowband perfect OA, and its operating frequency can be continuously tuned by changing the Fermi level. Our results will promote the development of graphene-based applications in THz and infrared regimes.

Broadband near-perfect optical absorbers fabricated with complete spherical platinum shells with and without induced symmetry broken cracks using a simple colloidal route

Broadband perfect absorbers with an average absorptivity of 96.2% in the 200–1500 nm are proposed. Complete spherical Pt shells with induced cracks are fabricated from monolayer microspheres along with heating using conformal oxide and metal coating.

Dual functional metasurface with broadband polarization conversion and perfect absorption

A dual-functional metasurface based on vanadium dioxide (VO2) and operating in the infrared region is proposed in this paper. The photonic metasurface consists of a double-split ring resonator and the gaps are loaded with VO2 to achieve dual-functionality. The proposed metasurface functions as a polarization converter at a temperature (T) of 358 K when VO2 is in insulating state. In this state, broadband linear to cross polarization is achieved with an excellent polarization conversion ratio (PCR) of > 98% in the 2702–4687 nm wavelength range. At a lower temperature (303 K), VO2 is in the metallic state and the metasurface functions as a wideband absorber with an absorptivity of > 90% in the wavelength range from 3896 − 4615 nm. There is a significant overlap in the frequency responses of the absorber and polarization converter leading to dual-functional behavior of the metasurface. Therefore, the structure is thermally tunable and suitable for optical and photonic applications.

Bi-Channel Switchable Broadband Terahertz Metamaterial Absorber

In this letter, a novel and simple design of switchable broadband terahertz metamaterial absorber is theoretically proposed and numerically demonstrated. The electrically adjusting material of graphene and the temperature-related phase-change material of vanadium dioxide (VO2) are combined in such multi-channel manipulation design. When VO2 is set to be the state of dielectric, the designed platform serves as a broadband absorber with an absorption rate exceeding 90% in the range of 1.31-3.18 THz, and simultaneously the absorption rate can be artificially adjusted from 5.3% to 99.0% at 2.8 THz by adjusting the Fermi energy level of graphene from 0 to 1 eV. When VO2 is set to be the state of metal, the absorber can achieve broadband perfect absorption in the large frequency range of 4.45-8.40 THz. It should be noted that such two broadband absorption windows are remarkably separated in the spectral range, indicating the impressive promise for switching operation during the applications. Due to the symmetry of the structure, the broadband absorber is insensitive to the polarization angle and has good performance in the range of high incidence angle. The design and the findings hold potential applications in the terahertz wave technologies, such as intelligent switching and tunable filtering.

Ultra-Broadband Perfect Absorber based on Titanium Nanoarrays for Harvesting Solar Energy.

Solar energy is a clean and renewable energy source and solves today's energy and climate emergency. Near-perfect broadband solar absorbers can offer necessary technical assistance to follow this route and develop an effective solar energy-harvesting system. In this work, the metamaterial perfect absorber operating in the ultraviolet to the near-infrared spectral range was designed, consisting of a periodically aligned titanium (Ti) nanoarray coupled to an optical cavity. Through numerical simulations, the average absorption efficiency of the optimal parameter absorber can reach up to 99.84% in the 200-3000 nm broadband range. We show that the Ti pyramid's localized surface plasmon resonances, the intrinsic loss of the Ti material, and the coupling of resonance modes between two neighboring pyramids are highly responsible for this broadband perfect absorption effect. Additionally, we demonstrate that the absorber exhibits some excellent features desirable for the practical absorption and harvesting of solar energy, such as precision tolerance, polarization independence, and large angular acceptance.

THz broadband and dual-channel perfect absorbers based on patterned graphene and vanadium dioxide metamaterials.

This paper proposes a novel and perfect absorber based on patterned graphene and vanadium dioxide hybrid metamaterial, which can not only achieve wide-band perfect absorption and dual-channel absorption in the terahertz band, but also realize their conversion by adjusting the temperature to control the metallic or insulating phase of VO2. Firstly, the absorption spectrum of the proposed structure is analyzed without graphene, where the absorption can reach as high as 100% at one frequency point (f = 5.956 THz) when VO2 is in the metal phase. What merits attention is that the addition of graphene above the structure enhances the almost 100% absorption from one frequency point (f = 5.956 THz) to a wide frequency band, in which the broadband width records 1.683 THz. Secondly, when VO2 is the insulating phase, the absorption of the metamaterial structure with graphene outperforms better, and two high absorption peaks are formed, logging 100% and 90.7% at f3 = 5.545 THz and f4 = 7.684 THz, respectively. Lastly, the adjustment of the Fermi level of graphene from 0.8 eV to 1.1 eV incurs an obvious blueshift of the absorption spectra, where an asynchronous optical switch can be achieved at fK1 = 5.782 THz and fK2 = 6.898 THz. Besides, the absorber exhibits polarization sensitivity at f3 = 5.545 THz, and polarization insensitivity at f4 = 7.684 THz with the shift in the polarization angle of incident light from 0° to 90°. Accordingly, this paper gives insights into the new method that increases the high absorption width, as well as the great potential in the multifunctional modulator.

Ultrathin Broadband Metasurface Superabsorbers from a van der Waals Semimetal

AbstractMetamaterials and metasurfaces operating in the visible and near‐infrared (NIR) offer a promising route towards next‐generation photodetectors and devices for solar energy harvesting. While numerous metamaterials and metasurfaces using metals and semiconductors have been demonstrated, semimetals‐based metasurfaces in the vis‐NIR range are notably missing. This work experimentally demonstrates a broadband metasurface superabsorber based on large area, semimetallic, van der Waals platinum diselenide (PtSe2) thin films in agreement with electromagnetic simulations. The results show that PtSe2 is an ultrathin and scalable semimetal that concurrently possesses high index and high extinction across the vis‐NIR range. Consequently, the thin‐film PtSe2 on a reflector separated by a dielectric spacer can absorb >85% for the unpatterned case and ≈97% for the optimized 2D metasurface in the 400–900 nm range making it one of the strongest and thinnest broadband perfect absorbers to date. The results present a scalable approach to photodetection and solar energy harvesting, demonstrating the practical utility of high index, high extinction semimetals for nanoscale optics.

High-efficiency broadband perfect absorber based on a multilayered pyramid structure

In this paper, an ultra-broadband perfect absorber based on a four-layer pyramid metamaterial and a metal insulator metal (MIM) structure has been demonstrated and investigated. Finite-difference time-domain (FDTD) results indicate that the absorption originates from localized surface plasmons and waveguide mode resonance effect. An average absorption of 96.18 % with bandwidth ranging from 308 nm to 2387 nm was achieved, and the average absorption in the entire wave band (200–2800 nm) was approximately 94.64%. The results of the impedance matching theory are consistent with the FDTD simulation. Polarization insensitivity was investigated by studying the absorption characteristic of TE and TM polarizations. The effect of top and bottom materials was investigated and compared in detail. Moreover, by adjusting the geometrical size, the absorption performance can be fine- tuned. In addition, the proposed broadband absorber exhibited excellent absorption stability and environmental refractive index tolerance. Without noble metal materials, the proposed structure can reduce the fabrication costs. We believe that the proposed broadband absorber has potential applications in solar cells, infrared imaging, and thermal emitters.

Nanoengineered nickel-based ultrathin metamaterial absorber for the visible and short-infrared spectrum

Nanostructured-based broadband perfect absorbers are of great interest in a wide range of applications, including spectroscopy, energy harvesting, and thermal photonics, etc. Here, a planar square meta-ring of nickel (Ni) is presented, which has the potential to absorb a large operational wavelength starting from 400 nm to 3000 nm. The proposed device model comprises a configuration of three layers with a top and bottom metal of Ni and a middle dielectric layer of aluminium nitride (AlN). The designed square ring metamaterial absorber (SRMMA) can attain an average absorption value of more than 90% over a large waveband from 400-3000 nm. Moreover, it can also maintain its absorption value up to 70% for oblique incident angles for both the wave polarization cases (TE and TM). Furthermore, it also exhibits the polarization-insensitive absorption response under the influence of different polarization angles, which is attributed to the four-fold symmetry in the geometry of the square meta-ring. Furthermore, our SRMMA also reduces fabrication complexity and cost due to its simplified design architecture. These promising features of the proposed SRMMA may have widespread applications in solar energy harvesting, thermal emission, and other optoelectronic devices.

Simulated Performance of a Broadband Solar Absorber Composed of Sectioned Au Disk Structures and ZnS/Au Thin Layers

Solar energy is considered an essential source of energy because of cleanliness and ubiquity. However, how to effectively absorb solar energy within the range of solar radiation is an urgent problem to be solved. The design of high-performance broadband perfect absorbers is an important way to collect solar energy efficiently. In this paper, we propose a novel broadband solar energy absorber based on zinc sulfide (ZnS). It is a three-layer (Au-ZnS-Au) structure with new types of sectioned disks employed in the top layer. The sectioned disks can enhance the absorption efficiency. Surface plasmon polariton (SPP) and electric dipole resonance increase the absorption of light, so the proposed absorber can achieve broadband perfect absorption. Simulation by a finite element analysis (COMSOL) method shows that absorption with a bandwidth of 354 THz from 430 THz–784 THz has been achieved, and the average absorption is 95%. This indicates that the perfect absorption range of the proposed absorber is 78.7% of the visible range. The perfect absorber has four perfect absorption peaks, which can reach a maximum absorption rate of 99.9%. In addition, our absorber is polarization insensitive due to the design of the rotational symmetry structure of the sectioned disks. The absorber is composed of refractory metals so that it can work under actual solar radiation and high-temperature conditions. The proposed solar energy absorber is important for many applications such as solar cells, thermal photovoltaic technology, and sensing.

A broadband perfect metamaterial absorber with angle-insensitive characteristics

A broadband perfect metamaterial absorber (MA) based on bilayer resistive films with different structure units is proposed in the microwave regime. An equivalent circuit model based on transmission line theory is established to guide the absorber design and explain its broadband and perfect absorption mechanism. The absorber characters high absorptivity and stable angular. The MA displays more than 98% absorption from 4.9 to 22.6 GHz at normal incidence. The performance is suitable for transverse electric (TE) and transverse magnetic (TM) waves at normal incidence, while absorption is better than 90% (80%) within the oblique incidence 50° (60°). The measured results of absorption and 10 dB radar cross section (RCS) agree well with the simulated ones.

Surface plasmon resonance-enhanced broadband perfect absorption in a Ti3C2Tx-based metamaterial absorber

The absorption band in which near-unity or perfect absorption can be realized is still narrow in the current broadband metamaterial absorbers (BMAs). In this article, a broadband perfect metamaterial absorber (BPMA) based on surface plasmon resonance (SPR) is proposed for the visible and near-infrared range. The BPMA composed of a patterned Ti3C2Tx layer, SiO2 layer and the ground gold layer can offer over 90% absorption across the wavelength range of 639–967 nm. It is worth noting that near-unity absorption can be achieved in the range 728–890 nm, which is out of reach by the currently reported BMA. The electric field distribution reveals that localized SPR generated by the Ti3C2Tx layer contributes to the broadband perfect absorption. Additionally, the BPMA is insensitive to incident and polarized angles at TE and TM modes. The calculated results based on interference theory agree well with the simulation results, thus supporting the design. This work may provide a potential approach to broadband perfect absorption in the visible and near-infrared region.

Tri-functional metamaterials integrated with vanadium dioxide in terahertz regions

In this paper, we theoretically and numerically demonstrate a vanadium dioxide (VO2)-based metamaterial device with triple functionalities in the terahertz region. By altering the phase transition characteristic of VO2, broadband perfect absorption and asymmetric transmission (AT) can be switchable obtained in a wideband frequency regime. When VO2 operates in the conducting state, the designed metamaterial acts like a polarization-dependent broadband perfect absorber. The absorbance is above 95% for x-polarized lights in the frequency range from 5.2 to 7.1 THz, while the absorbance is as low as 20% when the polarization is along the y-axis. When VO2 serves in the insulating state, the designed metamaterial device exhibits an AT effect with efficiency ∼0.72 in terahertz regions. Moreover, broadband polarization conversion associated with the asymmetric transmission can be achieved in the terahertz region. The electric field distributions combined with the current vectors are introduced to explore the physical mechanism. Besides, the performance of proposed metamaterial can be adjusted by altering the structural parameters. This designed metamaterial may have potential applications in exploring optoelectronic devices, such as optical switching, optical diode and thermal emitters in THz frequencies.

Polarization-insensitive broadband perfect metamaterial absorber in the optical region

Metamaterials (MTMs) have various applications like plasmonic sensors, light trapping, light detector, color imaging, real invisible clock, magnetic resonance imaging, thermal imaging, solar cells, etc. We have used CST software to simulate four nano-rings-based broadband MTM absorbers in this paper. The simulated structure consists of three layers in the form of a metal-dielectric-metal that exhibit a good impedance near unity with plasmonic resonance characteristics. Tungsten (W) is chosen as the metal and silicon dioxide (SiO2)as the dielectric. The designed structure exhibits an average absorption of 98.19% at the applied wavelength and also exhibits broadband absorption with almost perfect absorption. The physical dimensions, as well as the design of the proposed absorber, have been studied parametrically. Absorber performance has been investigated for transverse electric (TE) and transverse magnetic (TM) modes at wide angles up to 50°, which may be helpful for solar thermo-photovoltaic (STPV) and solar power harvesting device applications. For solar cell applications, we have calculated numerical values of short circuit current density (Jsc) and efficiency (η).

On the design of non-Hermitian elastic metamaterial for broadband perfect absorbers

Elastic metamaterial, an engineered artificial material, has received much attention in physics and engineering communities due to its functional properties unavailable in natural materials. However, most elastic metamaterials, especially for their two-dimensional structures, belong to the Hermitian category, making them difficult to adapt to real lossy structures and explore their loss modulation. In the present study, non-Hermitian loss-modulation beam and plate models based on complex wavenumber plane, structural dynamics, and mode-coupling scattering theory are established to design lossy elastic metamaterials (LEMs) for any solid material. Based on a unified closed-form solution for absorption, the subwavelength lightweight LEM can cope with the conventional challenge of achieving broadband and near-omnidirectional elastic wave perfect absorption. We reveal here the high-performance absorption of the LEM from greatly enhanced wave-energy dissipation by a combination of dissipation-radiation-balance and multiple reflections in the non-Hermitian elastic wave system. We numerically and experimentally verify the effectiveness of the theoretical model and demonstrate broadband and perfect absorption in a plate-like structure. Our work not only opens a new route to achieve broadband low-frequency vibration suppression in macro devices and microelectromechanical systems, more essentially, but it also provides an effective paradigm to wave engineering in non-Hermitian elastic wave systems.

Bidirectional visible light absorber based on nanodisk arrays

A perfect bidirectional broadband visible light absorber composed of titanium nitride and tungsten nanodisk arrays is proposed. The average absorption of the absorber exceeds 89% at 400 nm–800 nm when light is normally incident on the front-side. Illumination from the opposite direction (back-side) results in absorption of more than 75%. Through the theoretical analysis of the electric and magnetic fields, the physical mechanism of the broadband perfect absorption is attributed to the synergy of localized surface plasmons, propagating surface plasmons, and plasmonic resonant cavity modes. Furthermore, the absorber also exhibits excellent polarization-independence performance and a high angular tolerance of ∼ 30° for both front- and back-side incidence. The designed bidirectional broadband visible light absorber here has wide application prospects in the fields of solar cells and ink-free printing.

Design of a Broadband Perfect Solar Absorber Based on a Four-Layer Structure with a Cross-Shaped Resonator and Triangular Array

As solar energy is a low-cost and clean energy source, there has been a great deal of interest in how to harvest it. To absorb solar energy efficiently, we designed a broadband metamaterial absorber based on the principle of Fabry–Pérot (FP) cavities and surface plasmon resonance (SPR). We propose a broadband perfect absorber consisting of a four-layer structure of silica–tungsten–silica–titanium (SiO2–W–SiO2–Ti) for the incident light wavelength range of 300–2500 nm. The structure achieves perfect absorption of incident light in the wavelength range of 351.8–2465.0 nm (absorption > 90%), with an average absorption of 96.3%. The advantage of our proposed structure is that it combines the characteristics of both high and broadband absorption, and has high overall absorption efficiency for solar radiation. It is also independent of polarization and insensitive to incident angle. We investigated how absorption was affected by different structures, materials, geometric parameters, and refractive indices for different dielectric materials, and we explored the reasons for high absorption. This structure is refractory and ultrathin, and it offers a good tradeoff between bandwidth and absorption. It therefore has premium application prospects and value.