Graphene can be utilized as a tunable material for a wide range of infrared wavelength regions due to its tunable conductivity property. In this paper, we use Y-shaped silver material resonator placed over the top of multiple graphene silica-layered structures to realize the perfect absorption over the infrared wavelength region. We propose four different designs by placing the graphene sheet over silica. The absorption and reflectance performance of the structures have been explored for 1500- to 1600-nm wavelength range. The proposed design also explores the absorption tunability of the structure for the different values of graphene chemical potential. We have reported the negative impedance for the perfect absorption for proposed metamaterial absorber structures. All the metamaterial absorbers have reported 99% of its absorption peaks in the infrared wavelength region. These designs can be used as a tunable absorber for narrowband and wideband applications. The proposed designs will become the basic building block of large photonics design which will be applicable for polariser, sensor, and solar applications.
相似文献In this paper, the idea of square fractal geometry has been utilized to introduce a tunable wideband graphene-based perfect plasmonic absorber in the near-infrared region. It consists of a MgF2 layer and an array of gold squares fractal loaded on a graphene layer. In the designed absorber a single layer of graphene has been used instead of multilayered graphene structures. The structure is polarization-insensitive under normal incidence due to the geometric symmetry. The absorption and bandwidth of the structure are almost insensitive to the incident angle up to 15° and 45° for TE and TM polarizations, respectively. Moreover, by choosing appropriate structural parameters, the resonance wavelength of the desired plasmonic absorber can be controlled. The absorption of the introduced structure can be tuned by changing the chemical potential of the graphene. Therefore, the proposed fractal absorber can act as switch and inverter at λ = 1995 nm. Furthermore, the equivalent circuit model of the absorber has been derived to confirm the validity of the simulation results. The superiorities of our fractal absorber are wide full-width at half-maximum of 406 nm, multi-applicant, perfect absorption, and fabrication feasibility due to the simple structure with the maximum absorption tolerance error of 5.12%.
相似文献In this paper, a graphene-based tunable multi-band terahertz absorber is proposed and numerically investigated. The proposed absorber can achieve perfect absorption within both sharp and ultra-broadband absorption spectra. This wide range of absorption is gathered through a unique combination of periodically cross- and square-shaped dielectrics sandwiched between two graphene sheets; the latter enables it to offer more absorption in comparison with the traditional single-layer graphene structures. The aforementioned top layer is mounted on a gold plate separated by a Topas layer with zero volume loss. Furthermore, in our proposed approach, we investigated the possibility of changing the shapes and sizes of the dielectric layers instead of the geometry of the graphene layers to alleviate the edge effects and manufacturing complications. In numerical simulations, parameters, such as graphene Fermi energy and the dimensions of the proposed dielectric layout, have been optimally tuned to reach perfect absorption. We have verified that the performance of our dielectric layout called fishnet, with two widely investigated dielectric layouts in the literature (namely, cross-shaped and frame-and-square). Our results demonstrate two absorption bands with near-unity absorbance at frequencies of 1.6–2.3 and 4.2–4.9 THz, with absorption efficiency of 98% in 1.96 and 4.62 THz, respectively. Moreover, a broadband absorption in the 7.77–9.78 THz is observed with an absorption efficiency of 99.6% that was attained in 8.44–9.11 THz. Finally, the versatility provided by the tunability of three operation bands of the absorber makes it a great candidate for integration into terahertz optoelectronic devices.
相似文献A tunable multi-band metamaterial perfect absorber is designed in this paper. The absorber made of a composite array of gold elliptical and circular disks on a thick metallic substrate, separated by a thin dielectric spacer. The absorptivity and the field enhancement of proposed structures are numerically investigated by the finite difference time domain method. Three absorption peaks (1.15, 1.55, and 2.05 μm) with the maximal absorption of 99.2, 99.7, and 97.3% have been achieved, respectively. By altering the dimensions of associated geometric parameters in the structure, three resonance wavelengths can be tuned individually. Physical mechanism of the multi-band absorption is construed as the resonance of magnetic polaritons. And the absorber exhibits the characteristics that are insensitive to the polarization angle due to its symmetry. The research results can have access to selective control of thermal radiation and the design of multi-band photodetectors.
相似文献We present a multi-band terahertz absorber formed by periodic square metallic ribbon with T-shaped gap and a metallic ground plane separated by a dielectric layer. It is demonstrated that absorption spectra of the proposed structure consist of four absorption peaks located at 1.12, 2.49, 3.45, and 3.91 THz with high absorption coefficients of 98.0, 98.9, 98.7, and 99.6%, respectively. It is demonstrated that the proposed absorber has the tunability from single-band to broadband by changing the length of square metallic ribbon and we can also select or tune the frequencies which we want to use by changing polarization angles. Importantly, the quality factor Q at 3.91 THz is 30.1, which is 5.6 times higher than that of 1.12 THz. These results indicate that the proposed absorber has a promising potential for devices, such as detection, sensing, and imaging.
相似文献The need for an easy to fabricate perfect and narrowband light absorber in the visible range of electromagnetic (EM) spectrum has always been in demand for many scientific and device applications. Here, we propose a metal-dielectric-metal (MDM) 1-D grating plasmonic structure as a perfect narrow band light absorber in the visible and its application in glucose detection. The proposed structure consists of a 1- D grating of gold on the top of a dielectric layer on a gold film. Optimization for dielectric grating index (n), grating thickness (t), grating width (W), and grating period (P) has been done to improve the performance of plasmonic structure by calculating its quality factor and figure-of-merit (FOM). The optimized plasmonic structure behaves as a perfect narrowband light absorber. The flexibility to work at a specific wavelength is also offered by the proposed structure through an appropriate selection of the geometrical parameters and refractive index of the dielectric grating. The equivalent RC model is used to understand different components of the proposed structure on the optical response. The absorption response of the structure is invariant to the incident angle. Moreover, the calculated absorbance of the proposed plasmonic structure is ~ 100% with a narrow full-width half maxima (FWHM) of ~ 2.8 nm. We have numerically demonstrated a potential application of the proposed MDM absorber as a plasmonic glucose sensor in the visible range with detection sensitivity in the range of 140 to 195 nm/RIU.
相似文献A five-band polarization-insensitive perfect metamaterial absorber (PMA) is reported in this paper for THz detection and sensing applications. The proposed absorber is constructed using interconnected circular ring elements enclosed by a square loop. The ring elements are interconnected using short strip lines which increases the electrical length to offer resonance at the lower frequencies of the THz regime without increasing the electrical length. The proposed absorber has a footprint of 0.12 λeff?×?0.12 λeff where λeff is the effective wavelength calculated at the lowest operating frequency. The absorber provides 92%, 84%, 90%, 100%, and 100% absorption at 0.24, 0.56, 0.65, 0.82, and 0.95 THz, respectively. The proposed structure offers structural symmetry, and hence, it is polarization-insensitive. The proposed five-band absorber has good angular stability consistent with many research works reported in the literature and has a small frequency ratio of 1:2.3:2.7:3.4:3.9. The proposed absorber can be used as a permittivity sensor and its sensitivity is estimated to vary from 5.8 GHz/permittivity unit (PU) to 23.56 GHz/PU.
相似文献In this study, we present a high-performance tunable plasmonic absorber based on metal-insulator-metal nanostructures. High absorption is supported over a wide range of wavelengths, which is retained well at a very wide range of incident angles too. The coupling process occurs with high absorption efficiency of ∼ 99% by tuning the thickness of the dielectric layer. In addition, a complex trapezoidal nanostructure based on simple metal-insulator-metal structures by stacking different widths of Cu strip-nanostructures in the vertical direction has been put forward to enhance light absorption based on selective absorption. A trapezoidal sample has been designed with a solar absorption as high as 95% at wavelengths ranging from 300 nm to 2000 nm for different operating temperatures. Furthermore, the optical absorber has a very simple geometric structure and is easy to integrate into complex photonic devices. Perfect absorption and easy fabrication of the metal-insulator-metal structure make it an attractive device in numerous photonic applications.
相似文献In this article, a terahertz absorber tuned by temperature field with a newfangled structure is presented, which comprises the mercury resonators. In this scheme, temperature (T) build-up will lead the mercury stored in the bottom slot to expand through the columniform hole and be full of the upper central cross container, which can transform the absorption bands of such an absorber. The simulated results manifest that when T is increased from 0 to 25 °C, the dual-frequency absorption points (2.59 THz, 3.03 THz) and a narrow absorption region over 90% (6.54–7.10 THz), whose relative bandwidth (RB) is 7.9%, will be tailored to a single-frequency point absorption (3.12 THz) and a broadband absorption area (6.00–7.21 THz, and RB = 18.3%). For figuring out the property of the absorber mentioned above, the impacts of incident and polarization angles along with some relevant parameters of the structure on the absorption property are investigated. In addition, for plainly expounding the physical mechanism of absorption, the distributions of the surface current diagrams of the presented absorber are calculated, as well as the electric field diagrams, the magnetic field diagrams, the power loss density diagrams, and the power flow density diagrams. The proffered scheme in this article may offer a novel idea for realizing the reconfigurable absorbers.
相似文献This paper presents a simple multi-band metamaterial absorber for terahertz applications. The unit cell of the proposed structure consists of a single square ring having gaps at the centers on three of its sides. The proposed absorber produces three absorption bands for all polarizations and hence the design can be considered as insensitive to polarization variation. It provides an average absorption of 96.92% for the TE polarization with a peak absorption of 99.44% at 3.87 THz and for the TM polarization, it provides an average absorption of 98.4% with a peak absorption of 99.86% at 3.87 THz. An additional absorption peak is observed for the TE polarization at 1.055 THz that gradually diminishes with the increase in polarization angle and completely vanishes for the TM polarization. Thus, the structure displays a hybrid polarization response with polarization insensitivity in three bands and polarization sensitivity in one band. Parametric analysis has been carried out validating the optimal selection of the design parameters. The simplicity of the design and its combined polarization sensitive and polarization insensitive absorption characteristics can find tremendous applications in the field of terahertz imaging and sensing.
相似文献Ensuring a good trade-off between high-quality factor (Q-factor) and polarization independency is a key challenge for designing practicable terahertz metamaterial devices. We propose a symmetric composite aluminum-structured metamaterial absorber to achieve high Q-factor beyond 80 and near-unity absorbance of arbitrary polarization waves in the terahertz regime. Ultrahigh Q-factor reaches 84, and polarization-independent absorption is as high as 99% for resonant frequency tuning from 7.58 to 8.97 THz, covering 14% of the standard THz gap. The geometric effect of the symmetric sublattice on resonant frequency tuning is analyzed. The large Q-factor and strong absorption by oblique incidence is discussed. Designed high-Q metamaterial perfect absorber has various applications, including terahertz hyperspectral imaging, filtering, and sensing.
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