Dual-band Absorber Research Articles

Dual-band polarization-independent maze-shaped absorber based on graphene for terahertz biomedical sensing

This paper introduces an adjustable metamaterial absorber in the terahertz spectrum with exclusive properties such as resistance to polarization variation. Although this absorber can operate in various applications like chemical and environmental industries, its captivating features in different refractive (RI) make it a good choice in sensing and biomedical applications such as cancer early detection, blood glucose monitoring, and detecting malaria mosquito bites. The structure originally includes four different layers from top to bottom: graphene/ SiO2/Si/Au, respectively. The finite integration technique has been used for simulation. In terms of absorbing parameters, the proposed structure reveals an outstanding absorption of 98.32% at 4.3 THz and 98.49% at 7.35 THz, with an average Q-factor of 8.92, by following simple absorption rules, simulation, and electric field distribution of the suggested structure, which is illustrated through diagrams to consider various parameters such as frequency, sensitivity, and physical mechanism.

Polaron hopping induced dual-band absorption in all amorphous cathodic electrochromic oxides

Polaron hopping induced dual-band absorption in all amorphous cathodic electrochromic oxides

Dual-band tunable absorber based on graphene-ITO composite metasurface

Dual-band tunable absorber based on graphene-ITO composite metasurface

Dynamically switchable multifunctional device for terahertz application using vanadium dioxide and graphene-based metasurface

Abstract In this article, a dynamically switchable and multifunctional metasurface is realized using a combination of vanadium dioxide (VO2) and graphene-based structures. The device can be tuned using the temperature transition property of vanadium dioxide from a wideband linear-to-circular polarization converter (LTCPC) to a wideband linear-to-linear cross polarization converter (LTLPC) and a dual-band absorber. The unit cell is designed with a gold-backed lossy-silicon dioxide (SiO2) substrate with a permittivity of 3.9, and the top metasurface layer is designed with a graphene-based dual triangle loaded split ring (DTLSR) and two stripes of vanadium oxide to cover the split partially. The proposed device can be used as a wideband LTCPC at normal temperature (298 K) from 1.43 THz to 2.85 THz, i.e., 66.35% fractional bandwidth (FBW). At temperatures greater than 341 K, VO2 exhibits metallic properties, and the structure functions as LTLPC from 1.82 THz to 3.31 THz (PCR ≥ 80%), i.e., 58.08 % FBW and maximum polarization conversion ratio (PCR) reported as high as 99.65 %. Furthermore, at this metallic condition, two absorption peaks are obtained at 1.22 THz and 3.30 THz with absorptivity of 93.5% and 100%, respectively. The device offers incident angle invariability up to 40° for LTCPC and up to 50° for LTLPC operation. Further insight into the mechanism of operation is developed using the surface current density and electric field distribution analysis. The advantage of the proposed metasurface over other similar structures is assessed with respect to multifunctional behavior, bandwidth, and stability under oblique incidence.

Dual-band photodetector based on a large circular dichroism

Room temperature near-infrared photodetector has important applications in military, aerospace, and other fields. However, the development of highly efficient and highly selective circularly polarized photodetectors is still a challenge. Here, we theoretically demonstrate a near-infrared photodetector based on the dual-band perfect absorber in a filleted L-shaped chiral dielectric metal metasurface, and the optical, thermal, and electrical properties are analyzed in detail. Numerical simulation results show that two absorption peaks at λ=1129 nm and λ=1148 nm under right-hander circularly polarized (RCP) are achieved, and the absorption rate is both greater than 90%, while the electromagnetic waves are almost completely reflected under left-hander circularly polarized (LCP), which indicates that the proposed system has strong optical chirality. Then, we investigate the effects of polarization angle and structure period on the absorption spectra. The relationship between the surface temperature of the thermo-sensitive material and the wavelength is calculated when the absorber is used as the heat source. Finally, two kinds of chiral photodetectors based on different effects, thermoelectric and pyroelectric effects, are designed, and the temperature time-varying relationship of the thermo-sensitive material is mainly discussed at λ=1129 nm. By constructing a complete external circuit, the correlated electrical properties of the system to the load are analyzed. This integrated photothermoelectric numerical simulation method can comprehensively consider the optical, thermal, and electrical effects so as to more accurately predict the overall performance of the photo-detection system in practical applications, which can significantly improve the overall efficiency of the system and achieve better energy utilization and performance.

Dual-band spin-dependent perfect absorber with anisotropic thin films in mid-infrared range

Abstract Motivated by the imperative demand for chirality manipulation within mid-infrared (mid-IR) range, this study presents an innovative solution to obtain selective perfect absorption and chiroptical responses with conventional Otto configuration. Optical responses of the structure have been calculated numerically by the 4×4 anisotropic transfer matrix method (ATMM). The results show that the proposal supports the chiral response with dual-band resonance in absorption spectra by displaying different properties for left-hand circular polarization (LCP) and right-hand circular polarization (RCP) light, its circular dichroism (CD) and working wavelength could be tuned by adjusting the layer thickness and incidence angle. It is demonstrated that the proposed device exhibits an extraordinary absorption efficiency of unity for RCP light and zero for LCP light at a wavelength of 9.32 μm, accompanied by a maximum CD in absorption of -1. The strategy in manipulating dual-band selective chiroptical (CO) responses holds great potential in realizing mid-IR devices capable of chirality manipulation.

A novel dual-band absorber for millimeter-wave RADAR applications

Abstract A linearly polarized dual-resonant millimeter-wave absorber for Radio Detection And Ranging (RADAR)applications is presented in this paper. The frequency-selective absorber (FSA) is composed of solitarily using the distributed elements. The proposed FSA achieves a dual-band resonance characteristic utilizing the mutual coupling between concentric square loops, the second harmonic mode of the Jerusalem cross, and the corrugated cross grids. The proposed dual-band FSA operates from 25.5 to 26.5 GHz (1 GHz) (fL) and 31.8 GHz–32.5 GHz (0.7 GHz) (fH) with minimum absorptivity of 96% and 92%, respectively. The desired frequency response of the proposed unit cell is demonstrated by an equivalent circuit model. The FSA prototype is fabricated and the simulated results are validated using experimental measurements. The proposed FSA is a suitable candidate for stealth application in defense and military systems.

A dual-band broadband absorber using frequency selective surface for satellite antenna.

A dual-band broadband absorber based on frequency selective surface (FSS) is proposed. This double-layer absorber consists of two layers of FSS structure; each layer has a unique construction and plays its wave-absorbing function in different frequency bands. In the low-frequency band, layer I is a transmission channel, and layer II effectively absorbs electromagnetic waves. Furthermore, layer I exhibits significant absorption characteristics in the high-frequency band, whereas layer II provides effective reflection. The combination of the two layers results in a remarkably effective absorption. Its reflectivity below - 10dB covers a bandwidth of 5.5-14.8GHz and 22.9-33.1GHz, and its fractional bandwidth is 128%. The structure prevents external electromagnetic interference from affecting the antenna's performance, ensuring communication quality in critical frequency bands while reducing unwanted absorption in unwanted frequency bands. It is worth mentioning that the structure still has good stability under 45° oblique incidence. The physical mechanism is analyzed in detail by using an equivalent circuit model (ECM). The measurement results are in good agreement with those of simulation and ECM.

A Triple-Tunable Dual-Band Metamaterial Absorber Based on Dirac Semimetal and InSb

The dynamically triple-tunable dual-band metamaterial absorber that can be electrically, thermally, and magnetically controlled is proposed in this paper. The absorber is composed of bulk Dirac Semimetal (BDS), SiO2, and InSb layers. The physical absorption mechanism can be analyzed theoretically by the equivalent circuit model (ECM) and electric field intensity distributions at absorption peaks. In the absence of applied magnetic field, based on the bright–bright coupling effect, the average absorption rate of dual-band absorber can reach 99.4% when the Fermi energy of the BDS is 0.13 eV and the temperature of the InSb is 475 K. When the applied magnetic field is along the X axis, the absorption frequencies and rates of dual-band absorber can be electrically tuned by adjusting the BDS Fermi energy and thermally and magnetically controlled by adjusting the InSb temperature and magnetic field. Furthermore, the impacts of parameters in dual-band absorbers and the application prospects of the dual-band absorber model as a refractive index sensor are further discussed. This work provides a theoretical basis for the designs of triple-tunable absorbers and sensors.

Theoretical design of an electrically and thermally dual-controlled double-band absorber based on graphene and InSb

A novel, to our knowledge, double-band metamaterial absorber based on graphene and InSb is proposed in the terahertz regime. The amplitude and center frequency of the absorber can be electrically tuned by adjusting the graphene chemical potential and thermally controlled by varying the InSb temperature independently. First, owing to the bright–bright mode coupling effect, the average absorption rate of double-band absorber can reach 97% in the FDTD simulation. Meanwhile, the physical absorption mechanism can be analyzed theoretically by the radiating two-oscillator model. Second, when the chemical potential of graphene increases, the absorption rates of the absorber decrease gradually, and the absorption frequencies are almost unchanged. Moreover, if the temperature of InSb increases, the absorption frequencies and rates of absorber increase simultaneously. Finally, the impact of parameters on the absorption spectra, and the excellent sensing performance of the dual-band absorber as a refractive index sensor, are further discussed. This work provides a theoretical basis for the designs of dual-tunable absorbers and sensors.

Design of dual peak star shaped metamaterial absorber for S and C band sensing applications

This paper presents the detailed design configuration and investigation of a small-scale dual-band metamaterial absorber (MTMA) for solid and liquid sensing applications. The overall dimension of the MTMA unit cell is 10 × 10 × 1.57 mm3 and constitutes an affordable FR-4 substrate. The absorber exhibits dual absorption peaks at 3.470 GHz for the S-band and 7.219 GHz for the C-band, respectively. Both absorption characteristics have been validated through comprehensive simulation and experimental procedures. The dual-band absorption rate exceeded 99% during simulations, and experimental validation showed an absorption rate above 98%. For sensing applications, various solid materials, including different Rogers substrates ( RT 5880, RT 5870, RT 4003 and RT 4835) and liquids such as sunflower and crown oil, were utilized. Our findings indicate that the proposed MTMA achieves a maximum Q-factor of 191 and a sensitivity of up to 2.5 for both solid and liquid sensing applications compared to previous studies. The simulation and experimental validation of the result indicate that suggested MTMA can be effectively used in different sensing applications such as the medical and communications industry.

All-semiconductor plasmonic type-II superlattice detector with dual-band absorption enhancement

All-semiconductor plasmonic type-II superlattice detector with dual-band absorption enhancement

3D-printed polarization-independent low-cost flexible frequency selective surface based dual-band microwave absorber

Abstract A 3D-printed polarization-independent low-cost lightweight and flexible frequency selective surface based dual-band microwave absorber is presented in this paper. Two concentric square loops fabricated at different heights using 3D printing technology are responsible for exhibiting dual-band responses at 3.32 GHz (S-band) and 5.46 GHz (C-band) with more than 97% absorptivities. The corresponding full widths at half maximum bandwidths are observed as 230 MHz (3.21–3.44 GHz) and 450 MHz (5.27–5.72 GHz). The proposed topology is polarization-insensitive owing to the four-fold symmetry. The absorption phenomenon is explained with the analysis of current distributions at the surface and impedance curves at the frequencies of resonance. Further, the performance has been evaluated for both planar and curved surfaces with different angles of curvature, and the good agreement between the measured and simulated responses confirms the flexible behavior of the proposed structure.

Design and performance of a dual-band plasmonic perfect absorber for infrared refractive index sensing

In this study, we introduce what we believe is an innovative design for a plasmonic perfect absorber (PPA) that is based on half-cut disk resonator metamaterials. This design exhibits remarkable stability and versatility, demonstrating effective functionality across a wide range of incident angles for both transverse electric (TE) and transverse magnetic (TM) polarization. The distinct operational characteristics of the PPA are highlighted by the presence of two corresponding absorption peaks at wavelengths of 870 and 1599 nm, where it achieves outstanding maximum absorption rates of 98.99% and 97.5%, respectively. The design’s ultra-narrow resonance peaks are indicative of its high-quality factors, which are vital for enhancing sensitivity in plasmonic sensory applications. This characteristic renders our PPA an exceptional candidate for refractive index (RI) sensing, where precision is critical. The dual-band perfect absorber (PA)-based sensor demonstrates significant RI sensitivity, with values approximately equal to 365 nm/RIU at the first absorption peak and 733 nm/RIU at the second. Our findings elucidate the exceptional potential inherent in this novel dual-band perfect absorber design. The versatility and efficiency across varied applications not only contribute to the existing body of knowledge but also pave the way for future advancements in plasmonic sensor technologies and metamaterial research.

Graphene-Based Dual-Band Metasurface Absorber with High Frequency Ratio.

In this paper, we propose a novel dual-band metasurface absorber with a high frequency ratio based on graphene. By carefully designing a centrally symmetrical graphene pattern and positioning it on a glass medium, while utilizing ITO as a ground, the metasurface absorber achieves remarkable high frequency ratio microwave absorption. Specifically, this metasurface absorber exhibits two distinct resonance points at 3.7 GHz and 14 GHz, with an impressive frequency ratio over 3.5. It achieves over 90% absorption efficiency in the frequency ranges of 3.5-4.5 GHz and 13.5-14.5 GHz, highlighting its capability to effectively absorb microwaves across widely spaced frequency bands. Furthermore, the metasurface absorber demonstrates optical transparency and polarization insensitivity, adding to its versatility and potential applications. The measured results of the fabricated prototype validate its design and potential for practical use.

A dual-band polarization independent dielectric metasurface-based absorber for sensing application in the visible light regime

We present a dual-band, polarization-independent dielectric terahertz absorber exhibiting near-perfect absorption and minimal reflection at frequencies of f 1 = 419 THz and f 2 = 528 THz. Using electromagnetic theory, we modeled the structure to derive the surface electric admittance and magnetic impedance of the metasurface, elucidating the conditions required for perfect absorption in terms of inverse electric and magnetic polarizabilities. The absorber features a tunable symmetrical design, facilitating precise frequency adjustment by modifying structural parameters and ensuring polarization independence for perpendicularly incident electromagnetic waves. This scalable and versatile absorber, constructed from readily available materials, is optimally suited for applications in resource detection, imaging, sensing, and medical diagnostics, attributed to its simplicity, cost-effectiveness, and high performance.

Multifunctionality in vanadium dioxide-integrated metamaterials for switching between dual-band perfect absorption and asymmetric transmission

In this work, we present a theoretical proposal for an actively tunable metamaterial design that integrates vanadium dioxide (VO2). This VO2-integrated design demonstrates the ability to switch between dual-band perfect absorption and asymmetric transmission (AT) functionalities in the near-infrared and mid-infrared spectral ranges. By utilizing the unique properties of VO2, our proposed device achieves broadband absorption across approximately 2.47 μm with polarization independence when VO2 is in its metallic state. Furthermore, it exhibits narrowband absorption with polarization correlation, reaching a linear dichroism value of approximately 0.704. On the other hand, when VO2 is in its insulating state, the metamaterial structure realizes AT of 0.418 for circularly polarized light. We provide physical insight into the operating mechanisms through impedance matching analysis and electric field distributions. The integration of VO2 in this dynamically tunable, multifunctional metamaterial design offers a novel approach to developing reconfigurable nanophotonic and nanosystem technologies.

Dual-narrowband terahertz metamaterial absorber based on all-metal vertical ring array for enhanced sensing application

In this paper, a novel design of a dual-narrowband metamaterial absorber (MMA) was proposed for using as a high-performance refractive index (RI) sensor in the terahertz (THz) region. The proposed MMA is based on a vertical-ring-shaped (VRS) structure gold film array. Through numerical simulation, it was found that the MMA can achieve high absorption levels of 99.8% and 94.6% at 1.723 THz and 2.457 THz, respectively, which are consistent with the values obtained using coupling mode theory (CMT). The MMA also exhibits high Q-factor values of about 27.35 and 102.38, respectively, which are close to the CMT values of 29.94 and 98.34. The dual-band strong absorption of the MMA is attributed to the guided modes of the critical coupling resonance, and the absorption properties can be adjusted by changing the geometrical parameters of the unit-cell structure. The proposed MMA has a narrowband and a higher Q-factor, making it suitable for RI sensing, with a sensitivity of about 1.66 and 1.88 THz RIU−1, and a figure-of-merit (FOM) of about 259.4 and 659.7 RIU−1, respectively. These findings open up new opportunities for the development of highly efficient MMAs, which have potential applications in biochemical sensing and detection in the THz region.

Vanadium dioxide-assisted switching of a half-wave and quarter-wave plate to a dual-band absorber for the terahertz wave

In this study, we present a broadband, multi-functional, and switchable metamaterial for terahertz (THz) waves. The metamaterial design achieves high polarization conversion efficiency and can seamlessly transition between a polarization converter (PC) and a dual-band absorber through the phase transition behavior of vanadium dioxide (VO2). Our design facilitates linear to-cross (Half-wave plate) and linear to-circular (Quarter-wave plate) polarization conversion across a bandwidth extending from 0.58 THz to 0.88 THz, and 0.35 THz to 0.50 THz respectively. Near-perfect absorption at 0.35 THz and 0.99 THz was observed when VO2 changed its phase from an insulator to a conductor. These broadband features are realized through a straightforward metamaterial design incorporating only a reflector, a dielectric spacer, and an antenna (meta-atom resonator). Our designed structure demonstrates impressive angular stability for incident angles ranging from 0° to 45°. The proposed switchable metamaterial holds promise for advancing the development of tunable polarization rotating devices and on/off switching LPC devices, offering broad applications in THz detection, sensing, and communications.

Tunable dual-band composite metasurface absorber in the mid-infrared region based on LSPs-SPPs interaction

Mid-infrared (MIR) region includes many important fingerprint signals about of particular chemical molecules and functional groups, which is an important band for compact optical sensing system. Controlling the localized surface plasmons (LSPs) and surface plasmon polariton (SPP) modes is an effective approach to achieving perfect absorption in plasmonic metasurfaces. In this work, we systematically investigate the interaction between LSP and SPP within a composite plasmonic metasurface absorber, as well as the impact of this interaction on its absorption characteristics. The absorber achieves absorptivity 99.2 % at 2.39 μm and 98.8 % at 3.61 μm. The detailed absorption mechanism and tunability of the absorber are discussed associated with a physical model based on quantum electron dynamics (QED) theory. Our analysis also explores the effect of incident angle, identifying a Rabi splitting at 40° and 3.61 μm due to the interaction between cavity modes and LSPs, while the absorption peak at 2.39 μm experiences a redshift with an increasing angle. These peaks show minimal dependence on the polarization angles of incident light. Furthermore, we investigate the impact of the SiO2 spacer's refractive index using an admittance model, observing a redshift in the absorption peaks with an increase in refractive index. Our findings not only introduce a metasurface absorber for the MIR spectrum, applicable in sensing and detection, but also establish a foundation for further research.