Proposed Absorber Research Articles

Lightweight and broadband metamaterial absorber based on ITO impedance film

In this paper, we present a lightweight, broadband metamaterial absorber that exhibits polarization stability and is insensitive to incident angles. The absorber is composed of one layer of indium tin oxide impedance surface, three layers of quartz fiber composite material, and one layer of paper honeycomb on a metal sheet. Our proposed absorber has a 90 % absorptivity bandwidth of 13.19 GHz, ranging from 4.83 GHz to 18.12 GHz at TEM plane wave normal incidence, covering the entire X and Ku band. We illustrate the variation of design parameters and the distribution of electromagnetic field and current to investigate the absorption mechanism. To demonstrate the effectiveness of our design, we fabricate a prototype sample and measure its absorption performance. The results show a bandwidth of 12.38 GHz, ranging from 4.91 GHz to 17.29 GHz, with a low profile of 0.095λL at the lowest operating frequency. The experimental results are in good agreement with the numerical simulation, effectively verifying our proposed design.

Thermal and electrical switchable wide-angle multi-band terahertz absorber.

Multi-band terahertz (THz) absorbers have recently gained attention due to their favorable application prospects in communication, imaging, detection, and other fields. However, many multi-band THz absorbers are tuned by a single method, which limits their tuning effect. To address this issue, we propose a multi-band THz absorber that can be co-modulated by thermal and electrical methods. Our proposed absorber uses vanadium dioxide (VO2) to achieve this co-modulation. When VO2 is insulating, the frequency of the absorbing peaks originating from the lateral Fabry-Pérot resonance mode can be changed by adjusting the VO2 width. When VO2 is a conductor, the quality factor of the absorbing peak based on the inductor-capacitor resonance mode can be tuned by adjusting the width of VO2. By varying the top dielectric layer thickness, the frequency of the absorbing peaks can be tuned over a wide range. For devices with two or three layers of graphene nanoribbons-dielectric stacks, a modulation effect similar to that of varying dielectric layer thickness in a single-layer graphene device can be achieved simply by applying a 1 eV Fermi energy to graphene nanoribbons in different layers. By combining thermal and electrical modulation, the two or three-layer stacked device can be dynamically switched between four or six absorbing states, and a wider range of dynamic peak frequency modulation can be realized. Furthermore, the performance of the absorber does not deteriorate significantly at an incident angle of up to 70°. Our proposed thermal-electrical switchable wide-angle multi-band THz absorber provides a reference for the design, fabrication, and application of high-performance THz absorbers in different fields.

Broadband tunable terahertz metamaterial absorber having near-perfect absorbance modulation capability based on a patterned vanadium dioxide circular patch

A new tunable broadband terahertz metamaterial absorber has been designed based on patterned vanadium dioxide (VO2). The absorber consists of three simple layers, the top VO2 pattern layer, the middle media layer, and the bottom metal layer. Based on phase transition properties of VO2, the designed device has excellent absorption modulation capability, achieving the functional transition from broadband absorption to near-perfect reflection. When VO2 is in the metallic state, there are two absorption peaks observed at frequencies of 4.16 and 6.05 THz, exhibiting near-perfect absorption characteristics; the combination of these two absorption peaks gives rise to the broadband phenomenon and the absorption bandwidth, where the absorbance exceeds 90% and spans from 3.40 to 7.00 THz, with a corresponding relative absorption bandwidth of 69.23%. The impedance matching theory, near-field patterns, and surface current distributions are provided to analyze the causes of broadband absorption. Furthermore, the broadband absorption could be completely suppressed when VO2 presents the dielectric phase, and its absorbance could be dynamically adjusted from 100% to less than 0.70%, thereby achieving near-perfect reflection. Owing to its symmetrical structure, it exhibits excellent performance in different polarization directions and at large incidence angles. Our proposed absorber may have a wide range of promising applications and can be applied in a variety of fields such as communications, imaging, sensing, and security detection.

Incident angle dependent tunable multiband infrared absorption based sensor

The effect of electromagnetic (EM) resonance in the graphene resonator and multiple reflections taking place in the dielectric spacer can provide the multiband infrared absorption. The intensity of resonance spectrum occurring due to the formation of EM dipoles in resonator can be controlled by patterning it using desired perturbation. The absorber response can be set with the multiple narrow and broad absorption peaks together by modulating the electrical properties of graphene material. The proposed absorber provides the incident angle dependent behavior with linear variation in the resonant wavelengths by maintaining the high absorption. This can provide a new way of tuning the antenna response by angle of incidence. The implemented absorber can provide the triple narrow bands which can be utilized for performing the refractive index sensing. The proposed absorber provides a significant value of sensing performance parameters including sensitivity, full-width-half-maxima, and figure-of-merit with the high value of quality factor. Moreover, the proposed absorber offers the ability of generating an extra narrow absorption band in the case of presence of sensing analyte of specific thickness and refractive index range making it highly sensitive for the detection of specific surroundings including the bio-cells, chemicals and humidity in the air. The broadband characteristics of the proposer absorber can be utilized in implementing the infrared EM shields and thermal storage components.

Triple-Band Anisotropic Perfect Absorbers Based on α-Phase MoO3 Metamaterials in Visible Frequencies.

Anisotropic materials provide a new platform for building diverse polarization-dependent optical devices. Two-dimensional α-phase molybdenum trioxides (α-MoO3), as newly emerging natural van der Waals materials, have attracted significant attention due to their unique anisotropy. In this work, we theoretically propose an anisotropic perfect metamaterial absorber in visible frequencies, the unit cell of which consists of a multi-layered α-MoO3 nanoribbon/dielectric structure stacked on a silver substrate. Additionally, the number of perfect absorption bands is closely related to the α-MoO3 nanoribbon/dielectric layers. When the proposed absorber is composed of three α-MoO3 nanoribbon/dielectric layers, electromagnetic simulations show that triple-band perfect absorption can be achieved for polarization along [100], and [001] in the direction of, α-MoO3, respectively. Moreover, the calculation results obtained by the finite-difference time-domain (FDTD) method are consistent with the effective impedance of the designed absorber. The physical mechanism of multi-band perfect absorption can be attributed to resonant grating modes and the interference effect of Fabry–Pérot cavity modes. In addition, the absorption spectra of the proposed structure, as a function of wavelength and the related geometrical parameters, have been calculated and analyzed in detail. Our proposed absorber may have potential applications in spectral imaging, photo-detectors, sensors, etc.

Tunable Ultra-Broadband Terahertz Waveband Absorbers Based on Hybrid Gold-Graphene Metasurface

In this paper, we propose a tunable ultra-broadband terahertz absorber based on hybrid gold-graphene resonator to achieve an ultra-broadband, ultra-thin, and tunable metasurface, which has not only the high absorption rate of gold metamaterials but also the tunable properties of graphene metamaterials, compared with the traditional single gold-based and graphene-based methods. By simulating the response frequencies by the finite element method, we found that the absorber achieves a broadband 2.68-7.48 THz range (absorption>80%) absorbance with a relative bandwidth of 94.5%, where the center frequency is f c=5.08THz. The physical mechanism of the absorber was analyzed using the electric field of the surface plasmon resonance, due to the design structure presents periodic geometric symmetry, the polarization angle and large angle incidence both present better advantages. The dynamic tuning of the metamaterial absorber is achieved by changing the Fermi energy level of graphene by adjusting the bias voltage to effectively control the metamaterial absorption intensity and resonant frequency. Our proposed absorber has important application prospects in sensing, optical communication, detection, and optical devices.