Ultra-broadband Perfect Absorber Research Articles

Switchable dual ultra-broadband perfect absorber based on graphene and vanadium dioxide hybrid metamaterials

Switchable dual ultra-broadband perfect absorber based on graphene and vanadium dioxide hybrid metamaterials

Ultra-broadband metamaterial absorber for collecting electromagnetic waves from the ultraviolet to the mid-infrared

Due to the inherent local limitations of surface plasmon resonance, it is challenging to design an ultra-broadband electromagnetic wave absorber covering multiple bands. In this paper, a novel Ultra-broadband perfect absorber is designed, which is a simple-type structure composed of metal-dielectric-metal (MDM), and the resonant cavity formed by metal and dielectric realizes high absorption. The calculated results of the absorber show that the average absorption rate in the range of 200–8000 nm is 95.70%, and the absorption bandwidth over 90% is 7800 nm. The ultra-broadband absorption can be attributed to the coupling effect of multiple resonances inside and outside the resonant cavity, which gives our proposed structure a wider bandwidth and higher light absorption capacity than the previously reported work and further reduces the complexity of the structure. When it is replaced by other materials, the structure also maintains high absorbency. In addition, the structure is not only polarization insensitive but also has wide-angle absorption, and it maintains high absorption in transverse magnetic (TM) mode and transverse electric (TE) mode. Even when the incident angle increases to 58°, the average absorption rate is still above 80%. It also has the characteristics of large process tolerance and strong adaptability to changing environments. These results allow the absorber to be applied in solar energy collection, infrared imaging and thermal detection, and optoelectronic devices.

Ultra-broadband perfect absorber based on sub-grating structure

This paper introduces an ultra-broadband perfect absorber. The absorber comprises just two layers. By introducing sub-grating structures in the groove of the rectangle grating, a broadband absorber is realized. The proposed structure operates in the wavelength range of 420nm-1543 nm, exhibiting an absorptivity greater than 90%. To enhance our comprehension of the physical mechanism behind broadband absorption, we analyze the distributions of current density, electric field, and magnetic field within the structure. The ultra-broadband absorption is achieved through multiple resonances of the structure. Additionally, the absorber demonstrates good absorption performance at large incident angles. By modifying the proposed structure to possess centrosymmetry, the absorber becomes impervious to incident waves with varying polarization angles. Owing to the simple structure, the absorber may have a wider range of applications, including photovoltaic devices and light-emitting devices.

Efficient photothermal therapy with spatially localized high-temperature generation by refractory absorber

In this work, we propose a titanium nitride (TiN)-based ultra-broadband perfect absorber from the ultraviolet to near-infrared wavelength ranges with the average absorptivity up to 96.7%. The weighted absorption efficiency of the solar radiation energy reaches 95.6%. In addition, photothermal therapy is conducted on such absorber, showing the effectively confined local high-temperature in the vicinity of the device. The steady-state temperature reaches 327 K at a depth of 3 mm beneath the tissue surface, leading to the efficient optical damage exceeding 90% for the surrounding diseased tissue only by a 3-min illumination. Such moderate photothermal therapy adequately meets the requirements for inactivating tumor cells and hold wide applications in the photo-biomedical science and technology.

Graphene Ultra-Broadband Perfect Absorber with Slit Structure

Graphene Ultra-Broadband Perfect Absorber with Slit Structure

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.

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.

Black Silicon Revisited as an Ultrabroadband Perfect Infrared Absorber over 20 μm Wavelength Range

Black silicon properties are investigated in the wavelength range extending from 0.2 to 25 μm with a focus on the mid‐infrared (MIR). It is demonstrated that concurrently increasing the initial level of doping of bare silicon, with given limits, enables reaching even higher absorptance and higher spectral range. Unprecedented light absorptance levels are obtained on black silicon with up to 99.5% in the spectral range from 1 to 8 μm and above 90% until 20 μm, leading to ultrabroadband, ultrablack silicon surfaces. The synergetic effects of morphology and volume doping are elucidated; in particular, how the high aspect‐ratio of conical nanostructures plays a crucial role. The experimental findings are analyzed with numerical simulations involving plasmonic effects of highly doped silicon and supported by tomographic processing of microscopy images. Guidelines and corresponding manufacturing routes are provided by which ultrabroadband, ultrablack silicon surfaces can be obtained within minutes of plasma processing, with no need for further functionalization. With the scalable manufacturing involving solely pure silicon, the resulting ultrabroadband perfect absorbers should be of benefit for large‐scale deployment of radiative cooling devices, blackbody infrared light sources, and infrared radiation sensing.

Ultra-broadband perfect absorber using triple-layer nanofilm in a long-wave near-infrared regime.

Plasmonic absorbers have received considerable attention because of their promising applications in solar cells, controllable thermal emission, and infrared detection. Most proposed plasmonic absorbers are fabricated with a precisely designed surface-pattern, which require complex manufacturing process and are costly. Herein, we propose a simple plasmonic absorber composed of a triple-layer Ti/SiO2/TiN nanosystem. The maximal absorption reaches 99.8% from 1554 nm to 1565 nm, and an average absorption of 95.3% is achieved in the long-wave near-infrared range (from 1100 nm to 2500 nm). The synergistic effect of the upper surface plasmon resonance and the Fabry-Perot resonance in the Ti/SiO2/TiN cause the high absorption. Additionally, the effects of the incident angle, polarization state, structural materials, and geometric parameters on the absorption performance are investigated in detail. The proposed near-infrared absorber has potential application prospects in solar collectors, thermal emitters, and solar cells, owing to its high absorption, ultra-broadband bandwidth, insensitivity to incident angle and polarization state, low cost, and simple preparation process.

Wafer-scale ultra-broadband perfect absorber based on ultrathin Al-SiO2 stack metasurfaces.

Broadband absorbers with high absorption, ultrathin thickness, and lithography-free planar structure have a wide range of potential applications, such as clocking and solar energy harvesting. For plasmonic metal materials, achieving perfect ultra-broadband absorption remains a challenge owing to the intrinsically narrow bandwidth. In this study, wafer-scale Al-SiO2 stack metasurfaces were experimentally fabricated to realize perfect ultra-broadband absorption. The experimental results show that the absorption for Al-SiO2 stack metasurfaces can reach up to 98% for the wavelength range from the ultraviolet to the near-infrared (350-1400 nm). It was experimentally verified that the absorption performance of Al-SiO2 stack metasurfaces is dependent on the layer number and is superior to that of other metal-based stack metasurfaces. This study will pave the way for development of plasmonic metal-based ultra-broadband absorbers as in low cost and high performance robust solar energy devices.

Ultra-broadband perfect terahertz absorber with periodic-conductivity graphene metasurface

We present an interesting scheme of ultra-broadband perfect terahertz (THz) absorber with periodic-conductivity graphene metasurface, instead of the common metasurfaces of geometrically patterned graphene with uniform conductivity. By exploiting periodic modulation of graphene conductivity, the graphene metasurface absorber produces a sequence of dense high-order resonance modes with near-perfect absorption peaks. The density of resonant modes can be largely enhanced to perform an ultra-broadband even continuum absorption in THz regime with suppression of the modulation minimum of graphene conductivity. Under the resistive loss effect of graphene on the modes broadening, the THz perfect absorber can perform a record ultra-broadband of 3.71 THz, which covers more than one-third of the whole THz region of 0.1–10 THz. Such scheme of periodic-conductivity graphene metasurface is of interest in pushing forward to broadband THz absorber, which has promising application prospects in THz stealth, imaging and communication fields.

Genetic-algorithm-aided ultra-broadband perfect absorbers using plasmonic metamaterials.

Complete absorption of electromagnetic waves is paramount in today's applications, ranging from photovoltaics to cross-talk prevention into sensitive devices. In this context, we use a genetic algorithm (GA) strategy to optimize absorption properties of periodic arrays of truncated square-based pyramids made of alternating stacks of metal/dielectric layers. We target ultra-broadband quasi-perfect absorption of normally incident electromagnetic radiations in the visible and near-infrared ranges (wavelength comprised between 420 and 1600 nm). We compare the results one can obtain by considering one, two or three stacks of either Ni, Ti, Al, Cr, Ag, Cu, Au or W for the metal, and poly(methyl methacrylate) (PMMA) for the dielectric. More than 1017 configurations of geometrical parameters are explored and reduced to a few optimal ones. This extensive study shows that Ni/PMMA, Ti/PMMA, Cr/PMMA and W/PMMA provide high-quality solutions with an integrated absorptance higher than 99% over the considered wavelength range, when considering realistic implementation of these ultra-broadband perfect electromagnetic absorbers. Robustness of optimal solutions with respect to geometrical parameters is investigated and local absorption maps are provided. Moreover, we confirm that these optimal solutions maintain quasi-perfect broadband absorption properties over a broad angular range when changing the inclination of the incident radiation. The study also reveals that noble metals (Au, Ag, Cu) do not provide the highest performance for the present application.

Long-Wave Infrared Ultra-Broadband Perfect Absorber with Embedded Structure

Long-Wave Infrared Ultra-Broadband Perfect Absorber with Embedded Structure

Ultra-broadband perfect absorber based on self-organizing multi-scale plasmonic nanostructures

Aside from well-performed light confinement, practical and scalable plasmonic perfect absorbers also depend on stable material scenario, as well as compact design and convenient fabrication. However, it still remains a challenge to make enclosed (no air exposure), multi-scale plasmonic nanostructure for constructing perfect absorbers. Herein, we report a direct self-organization growth of ultrathin (∼130 nm) multi-scale Ag nanostructures in SiO2 matrix on quartz or plastic substrates via sputtering. Based on the elaborate microstructure design, the cavity-mode excitation, local plasmon resonances and their lightning-rod effects are synergistically activated, yielding a near constant absorptance of over 95% across the 300–1700 nm wavelength even with some reflectance loss from the quartz surface and more than 98% visible absorptance with a simple antireflection treatment. Further, due to the enclosed nanostructures, the wide-angle absorbers present outstanding light-to-heat capability and thermal robustness under concentrated solar illumination. The simple material recipe (Ag, SiO2) and fabrication scheme suggest that our approach is with easy scalability. We anticipate that the proposed concept in this study can facilitate the rapid development of highly efficient ultrathin perfect absorbers.

Ultra-broadband absorber based on cascaded nanodisk arrays

An ultra-broadband perfect absorber consisting of cascaded nanodisk arrays is demonstrated by placing insulator–metal–insulator–metal nanodisks on insulator–metal film stacks. The absorber shows over 90% absorption in a wavelength range between 600 nm and 4000 nm under transverse magnetic (TM) polarization, with an average absorptivity of 91.5% and a relative absorption bandwidth of 147.8%. The analysis of the electric field and magnetic field show that the synergy of localized surface plasmons, propagating surface plasmons, and plasmonic resonant cavity modes leads to the ultra-broadband perfect absorption, which accords well with the results of impedance-matched analysis. The influences of structural parameters and different metal materials on absorption performance are discussed. Furthermore, the absorber is polarization-independent, and the absorption remains more than 90% at a wide incident angle up to 40° under TE polarization and TM polarization. The designed ultra-broadband absorber has promising prospects in photoelectric detection and imaging.

Ultra-broadband perfect absorber based on nanoarray of titanium nitride truncated pyramids for solar energy harvesting

A metamaterial perfect absorber working in the ultraviolet to near-infrared band is proposed based on a triple-layer structure composed of titanium nitride (TiN) periodic nanoarray, dielectric film, and TiN bottom layer. Each unit cell of the nanoarray is a truncated pyramid structure with its width tapered linearly from the bottom to the top. The physical mechanism of the absorber was explained by analyzing the electric field distributions at different wavelengths, and the absorption performance was simulated as a function of its geometric parameters and the angle and polarization of incident light as well. Optimal geometric parameters are presented. The absorber implemented using the optimal parameters would display an excellent performance with almost perfect absorption (above 99%) over the entire spectral region from 300 to 2500 nm. The ultra-broadband perfect absorption behavior is attributed to the localized surface plasmon resonance effect of the TiN pyramid, the intrinsic loss of the TiN material and the coupling of resonance modes between two adjacent pyramids. Besides, the absorber also exhibits a polarization-independent feature at normal incidence and good angular acceptance capability of incident light. The reported ultra-broadband metamaterial absorber shows great application prospects in the solar energy harvesting industry and solar thermophotovoltaic systems.

An ultra-broadband metasurface perfect absorber based on the triple Mie resonances

We report on an ultra-broadband metasurface perfect absorber in the visible and NIR region based on the triple Mie resonances generated from the three sets of nanopillars grown on SiO2 substrate. The polarization-independent and wide-angular-insensitive (up to 70°) high absorption is realized within a surface layer that is only 284 nm thick. Double-beam UV interference lithography and followed sputter coating depositions are utilized to efficiently fabricate the proposed metasurface structures. Experimental results demonstrate that the average absorption is 0.961 (0.970 in simulation) at the wavelength band ranging from 400 nm to 1800 nm, and works well even the incident angle is large as 70°. The demonstrated device suggests an efficient way of designing and fabricating ultra-broadband perfect absorber with metasurface structures, which has huge application prospects in advanced nanophotonic devices and integrated photonic systems.

Numerical study of an ultra-broadband perfect absorber from ultraviolet to near-infrared based on metal quadruple staircase structure

We present and numerically investigate a novel ultra-broadband polarization independent and incident angle insensitive absorber via simulation. It has a high average absorption of 98.74% from 300 nm to 2000 nm, and the maximum absorption reaches 99.995% within the band. This high absorption is the result of three propagating and localized surface plasmon resonance modes. The absorption stays above 90% at 45°incident angle, and above 80% at 60°. Without heavily stacked alternating materials, the design can reduce fabrication complexities. The adjustability of the structural parameters is demonstrated by designing an absorber covering 200 nm to 3000 nm with over 90% absorption. This proposed device can have promising applications in solar energy harvesting, optical imaging, and optical communications.

Polarization- and angle-insensitive ultrabroadband perfect metamaterial absorber for thermophotovoltaics

We report an ultrabroadband perfect metamaterial absorber, comprising a two-dimensional array of a hemi-ellipsoid shaped metallo-dielectric multilayered structure. What we believe, to the best of our knowledge, is an unprecedented average absorbance of ∼ 99 % is theoretically demonstrated in the 300 to 4500 nm spectral range at normal incidence. We use 20 pairs of molybdenum–germanium metallo-dielectric layers with tungsten as the ground metal placed on a silicon substrate. Our design is polarization-independent as well as angle-insensitive (up to 60°), making it a perfect “superabsorber.” Theoretical modeling based on effective medium theory validates our full-wave simulation results. The figure-of-merit calculations suggest that our superabsorber can outperform recently reported broadband absorbers. The proposed design has potential application in thermophotovoltaics for solar energy harvesting.

Analysis and design of InAs nanowire array based ultra broadband perfect absorber.

An ultra-broadband perfect absorber has a wide range of applications which include solar energy harvesting, imaging, photodetection etc. In this regard, InAs nanowire (NW) based structure is investigated in this work for achieving an ultra broadband perfect absorber. Finite difference time domain (FDTD) based numerical analysis has been performed to optimize the InAs nanowire based structure to obtain an efficient light absorber by varying different dimensional parameters. Mie theory and guided mode resonance based theoretical analysis is developed to validate the results and to get an insight into the tunability of the nanowire based structure. Moreover, the theoretical analysis elucidates the underlying physics of light absorption in nanowires. To achieve ultra broadband absorption, multi radii InAs nanowire based arrays are investigated and it is found that they exhibit superior performance compared to single radius NW based structures. The computed light absorption efficiency (LAE) and short circuit current density values are enhanced to 97% and 40.15 mA cm−2 at 10° angle of incidence for the optimized quad radii NW array within the wavelength range of 300 nm to 1000 nm and 300 nm to 1200 nm, respectively. Moreover, the absorption spectra for these structures are polarization independent and exhibit robust performance for varying angle of incidence. In addition, arrangement of the NW array (hexagonal or square) has negligible effect on the absorption spectra. Such ultra-broadband absorption capability of the proposed structure compared to existing works suggests that the InAs nanowire based structure is very promising as light absorber with prospects in the fields of photo detection, solar power generation, perfect cloaking, photochemistry and other thin film photonic devices.