Abstract-Terahertz absorber with dynamically switchable dual-broadband based on a hybrid metamaterial with vanadium dioxide and graphene

 

Yan Liu, Rui Huang, Zhengbiao Ouyang, 

(a) Schematic of the proposed absorber based on VO2-graphene metamaterials and the incident light polarization configuration. (b) Top view of the unit cell. (c) Side view of the unit cell.

https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-29-13-20839&id=452098

An absorber based on hybrid metamaterial with vanadium dioxide and graphene has been proposed to achieve dynamically switchable dual-broadband absorption property in the terahertz regime. Due to the phase transition of vanadium dioxide and the electrical tunable property of graphene, the dynamically switchable dual-broadband absorption property is implemented. When the vanadium dioxide is in the metallic phase, the Fermi energy level of graphene is set as zero simultaneously, the high-frequency broadband from 2.05 THz to 4.30 THz can be achieved with the absorptance more than 90%. The tunable absorptance can be realized through thermal control on the conductivity of the vanadium dioxide. The proposed device acts as a low-frequency broadband absorber if the vanadium dioxide is in the insulating phase, for which the Fermi energy level of graphene varies from to 0.1 eV to 0.7 eV. The low-frequency broadband possesses high absorptance which is maintained above 90% from 1.10 THz to 2.30 THz. The absorption intensity can be continuously adjusted from 5.2% to 99.8% by electrically controlling the Fermi energy level of graphene. The absorption window can be further broadened by adjusting the geometrical parameters. Furthermore, the influence of incidence angle on the absorption spectra has been investigated. The proposed absorber has potential applications in the terahertz regime, such as filtering, sensing, cloaking objects, and switches.

© 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Tunable terahertz metamaterial absorber based on electricity and light modulation modes

Jinfeng Wang, Tingting Lang, Zhi Hong, Tingting Shen, and Gangqi Wang

(a) Schematic view of the proposed tunable THz absorber. (b) Unit cell of the structure with geometrical parameters, the parameters of the absorber are set as p = 80 μm, t = 2 μm, h = 50 μm, b = 0.2 μm, a = 40 μm. The permittivity dispersion (real part: dotted line and imaginary part: solid line) of doped Si in the different layer under the pump fluence of 200 μJ/cm2 is shown on the middle.

https://www.osapublishing.org/ome/abstract.cfm?uri=ome-10-9-2262

In this paper, a metamaterial absorber that achieved absorption tuning by electricity and light control has been proposed in the terahertz (THz) regime. The THz absorber exhibits an absorbance of 97.5% at a resonant frequency of 0.245 THz. First, we simulated the absorption spectra under different structural parameters. Then the absorption characteristics are analyzed under different Fermi energies and pump fluences. When the Fermi energy changes from 0 to 1 eV, the peak absorbance decreases from 97.5% to 56.2%. As the fluence of the pump beam increases from 0 to 100 µJ/cm2, the peak absorbance decreases from 97.5% to 42.8%. The amplitude modulation depth T of our designed absorber is approximately 0.55. Electric and magnetic resonances are proposed in this article, which allows for nearly perfect absorption. Finally, the absorption for both transverse electric and transverse magnetic modes were investigated under different incident angles, from 0° to 75° with a step-width of 15°. The absorber can be potentially applied to THz detection, imaging, and sensing.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Ultra-broadband wide-angle terahertz absorber realized by a doped silicon metamaterial

Author links open overlay panelMingwei Jiang, Zhengyong Song, Qing Huo,


https://www.sciencedirect.com/science/article/abs/pii/S0030401820303308

Metamaterial absorber as a functional device has been extensively studied in the past decade, and its performance is continuously improved. Here we present a wide-angle terahertz absorber through polarization-insensitive doped silicon. The structural unit cell consists of a square silicon ring and a silicon substrate. Full-wave simulated results show that the designed absorber has excellent performance in the frequency range of 0.7-5.7 THz with the center frequency of 3.2 THz. The relative bandwidth ratio is 156.25% with absorptance greater than 90%. The design is insensitive to polarization at the small incident angle and still shows good performance over a wide range of incident angle. The proposed system may find potential applications in terahertz energy harvesting and thermal emission.

Abstract-A dynamically tunable terahertz metamaterial absorber based on an electrostatic MEMS actuator and electrical dipole resonator array

Fangrong Hu, Ningning Xu, Weiming Wang, Yue'e Wang, Wentao Zhang,  Jiaguang Han, Weili Zhang

https://iopscience.iop.org/article/10.1088/0960-1317/26/2/025006/meta

We experimentally demonstrate a dynamically tunable terahertz (THz) metamaterial absorber based on an electrostatic microelectromechanical systems (MEMS) actuator and electrical dipole resonator array. The absorption of the THz wave is mainly a result of the electrical dipole resonance, which shows a tunable performance on demand. By preforming the finite integral technique, we discovered that the central absorption frequency and the amplitude can be simultaneously tuned by the applied voltage U. Characterized by a white light interferometer and a THz time domain spectroscopy system, our THz absorber is measured to show a modulation of the central frequency and the amplitude to about 10% and 20%, respectively. The experimental results show good agreement with the simulation. This dynamically tunable absorber has potential applications on THz filters, modulators and controllers.

Abstract-A multi-band terahertz metamaterial absorber with novel structure

Wei Wei Meng, Jian Lv, Long Cheng Que, Yun Zhou, Ya Dong Jiang,

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10840/108401F/A-multi-band-terahertz-metamaterial-absorber-with-novel-structure/10.1117/12.2507451.short

A multi-band terahertz metamaterial absorber (MA) is proposed. The unit cell is formed by windmill-shaped elements in a square ring, a dielectric substrate and a metallic ground plane. The MA unit cell is investigated at normal and oblique incidence for both transverse electric (TE) and transverse magnetic (TM) polarizations. The simulated results show that the MA has three high absorption (greater than 99%) resonance narrow bands. The LC equivalent circuit is employed to analyze the origin of multi-band. The proposed MA is easy to fabricate, what’s more, the proposed MA has high absorption rate and insensitive to polarization, which is favorable for various applications, such as terahertz detecting, imaging, and so on.

© (2019) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Abstract-Improvement of multiband absorption with different technics (graphene, ito, and hole) for metamaterial absorber at optical frequencies

Batuhan Mulla,  Cumali Sabah

https://www.spiedigitallibrary.org/journals/Journal-of-Nanophotonics/volume-12/issue-4/046017/Improvement-of-multiband-absorption-with-different-technics-graphene-ito-and/10.1117/1.JNP.12.046017.short?SSO=1

Three absorption improvement techniques are numerically applied to a multiband metamaterial absorber design for solar energy harvesting. These techniques are the following: the reshaping of the back metallic plate, the integrating of graphene sheets, and the utilizing of indium tin oxide (ITO), in the design. Based on numerical simulation results, each of these methods has the capacity to enhance total absorption rates. In addition to the enhancement in the total absorption rates, new absorption peaks are also obtained within the various frequency regions (infrared and ultraviolet). Furthermore, the absorption enhancement abilities of the mentioned methods are also compared. Among all the techniques, ITO provides the highest absorption rates, as it enhanced the total absorption rate by 48.5%.

© 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)

Abstract-Ultra-wideband THz/IR Metamaterial Absorber based on Doped Silicon

Huafeng Liu, Kai Luo, Danhua Peng, Fangjing Hu, Liangcheng Tu

https://arxiv.org/abs/1809.09400

Metamaterial-based absorbers have been extensively investigated in the terahertz (THz) range with ever increasing performances. In this paper, we propose an all-dielectric THz absorber based on doped silicon. The unit cell consists of a silicon cross resonator with an internal cross-shaped air cavity. Numerical results suggest that the proposed absorber can operate from THz to mid-infrared, having an average power absorption of >95% between 0.6 and 10 THz. Experimental results using THz time-domain spectroscopy show a good agreement with simulations. The underlying mechanisms for broadband absorptions are attributed to the combined effects of multiple cavities modes formed by silicon resonators and bulk absorption in the substrate, as confirmed by simulated field patterns. This ultra-wideband absorption is polarization insensitive and can operate across a wide range of the incident angle. The proposed absorber can be readily integrated into silicon-based platforms and is expected to be used in sensing, imaging, energy harvesting and wireless communications systems.

Abstract-Terahertz dual-band metamaterial absorber based on graphene/MgF2 multilayer structures

Zhaoxian Su, Jianbo Yin, and Xiaopeng Zhao

http://65.202.222.105/oe/abstract.cfm?uri=oe-23-2-1679

We design an ultra-thin terahertz metamaterial absorber based on graphene/MgF2 multilayer stacking unit cells arrayed on an Au film plane and theoretically demonstrate a dual-band total absorption effect. Due to strong anisotropic permittivity, the graphene/MgF2 multilayer unit cells possess a hyperbolic dispersion. The strong electric and magnetic dipole resonances between unit cells make the impedance of the absorber match to that of the free space, which induces two total absorption peaks in terahertz range. These absorption peaks are insensitive to the polarization and nearly omnidirectional for the incident angle. But the absorption intensity and frequency depend on material and geometric parameters of the multilayer structure. The absorbed electromagnetic waves are finally converted into heat and, as a result, the absorber shows a good nanosecond photothermal effect.

© 2015 Optical Society of America

Abstract-Wide-angle perfect metamaterial absorbers based on cave-rings and the complementary patterns

Xiutao Huang, Conghui Lu, Cancan Rong, and Minghai Liu

https://www.osapublishing.org/ome/abstract.cfm?uri=ome-8-9-2520&origin=search

Wide-angle polarization-insensitive triple-band perfect metamaterial absorbers (PMAs) based on single resonators are investigated. Generally speaking, the single resonator can only generate an absorption peak induced by the excitation of a fundamental resonance. Here, the designed absorbers with a single cave-ring resonator appear three perfect peaks for different polarization angles at 6.53 THz, 7.09 THz and 7.64 THz. For the case of the transverse electric (TE) mode, the resonant peaks are controlled by the angle of incidence. Compared with previous studies about angular stability, the absorptivity still exceeds 92% around 6.53THz even when the incident angle for the TE mode is up to 80°. For the case of the transverse magnetic (TM) mode, the absorptance at 7.64 THz is still greater than 92% even up to 70°. Simulated electric field (Ez) and magnetic field (/H/) distributions indicate that perfect absorption arises from the excitation of the multipolar response and surface plasmons. Besides, the complementary structure also displays three absorption peaks. We have demonstrated that simple ultrathin PMA has good absorption stability under an oblique incidence up to 70° at 2.62 THz, and that the resonance frequency at 2.62 THz is almost unchanged for the incident angle ranging from 0° to 70°. These proposed absorbers may be used in many applications, such as THz imaging, sensors, and detectors.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Multi-mode Tunable Absorber Based on Graphene Metamaterial

Ning Hu, Peiguo Liu, Li-an Bian, Qihui Zhou, Chenxi, Liu Jihong Zhang, Hanqing Liu,


https://www.sciencedirect.com/science/article/pii/S0749603618310565

In this paper, a novel design of metamaterial absorber (MA) with multi modes and tunability characteristics in terahertz (THz) range is presented. The MA consists of patterned gold-graphene on the top layer, graphene sheet and gold ground separated by SiO2. The chemical potential of patterned graphene and graphene sheet can be tuned independently. Thus, the regulation flexibility of MA is greatly enhanced. For demonstration, the proposed MA is investigated using circuit analogy method and the distributions of the electric field are also discussed in detail to explore underlying mechanism. Numerical calculations are stimulated in a commercial full-wave solver and indicate that the proposed MA possesses excellent absorption properties. There are three perfect absorption ($\ge 99.2\text{\%}$) modes at 2.4 THz, 4.2 THz and 7.2 THz respectively. Under the regulation of chemical potential, the proposed MA could serve as single-frequency or dual-frequency absorber without change of physical structure. When working as single-frequency absorber, the MA could be regulated between different modes during a large frequency range and the absorption peaks could also be regulated within the same mode during a relative smaller frequency range. Furthermore, the MA has two absorption peaks at 2.4 THz and 7.2 THz ($\ge 95\text{\%}$) simultaneously as dual-frequency absorber. The proposed MA shows promising application potentials due to the flexible modulation and functions and this work provides a new perspective for the design of tunable THz absorbers based on graphene.

Abstract-Based on graphene tunable dual-band terahertz metamaterial absorber with wide-angle

Mulin Huang, Yongzhi Cheng, Zhengze Cheng, Haoran Chen, Xuesong Mao, Rongzhou Gong,

https://www.sciencedirect.com/science/article/abs/pii/S0030401818300646

We present a wide-angle tunable dual-band terahertz (THz) metamaterial absorber (MMA) based on square graphene patch (SGP). This MMA is a simple periodic array, consisting of a dielectric substrate sandwiched with the SGP and a continuous metallic film. The designed MMA can achieve dual-band absorption by exciting fundamental and second higher-order resonance modes on SGP. The numerical simulations indicate that the absorption spectrum of the designed MMA is tuned from 0.85 THz to 1.01 THz, and from 2.84 THz to 3.37 THz when the chemical potential of the SGP is increasing from 0.4eV to 0.8eV. Moreover, it operates well in a wide-angle of the incident waves. The presented THz MMA based on the SGP could find some potential applications in optoelectronic related devices, such as sensor, emitter and wavelength selective radiators.

Abstract-Ultrasensitive sensing with three-dimensional terahertz metamaterial absorber

Siyu Tan, Fengping Yan, Wei Wang, Hong Zhou, Yafei Hou,

http://iopscience.iop.org/article/10.1088/2040-8986/aab66e/pdf

Planar metasurfaces and metamaterial absorbers have shown great promise for label-free sensing applications at microwaves, optical and terahertz frequencies. The realization of high-quality-factor resonance in these structures is of significant interest to enhance the sensing sensitivities to detect the minute frequency shifts. We propose and demonstrate in this manuscript an ultrasensitive terahertz metamaterial absorber sensor based on three-dimensional split ring resonator absorber with a high quality factor of 60.09. The sensing performance of the proposed absorber sensor was systematically investigated through detailed numerical calculations and a maximum refractive index sensitivity of 34.40% RIU-1 was obtained. Furthermore, the absorber sensor can maintain a high sensitivity for a wide range of incidence angles up to 60° under TM polarization incidence. These findings would improve the design flexibility of the absorber sensors and further open up new avenues to achieve ultrasensitive sensing in terahertz regime.
© 2018 IOP Publishing Ltd

Abstract-Electrically tunable terahertz dual-band metamaterial absorber based on a liquid crystal

Zhiping Yin,  Yujiao Lu,  Tianyu Xia,  Weien Lai,  Jun Yang,  Hongbo Lua,  Guangsheng Deng,

http://pubs.rsc.org/en/content/articlelanding/2018/ra/c7ra13047c#!divAbstract

In this paper, a liquid crystal (LC) based tunable metamaterial absorber with dual-band absorption is presented. The proposed absorber is analysed both numerically and experimentally. The analysis shows that the two absorption peaks, originating from the new resonant structure, are experimentally detected at 269.8 GHz and 301.4 GHz when no bias voltage is applied to the LC layer. In order to understand the absorption mechanisms, simulation results for the surface current and power loss distributions are presented. Since liquid crystals are used as the dielectric layer to realize the electrically tunable absorber, a frequency tunability of 2.45% and 3.65% for the two absorption peaks is experimentally demonstrated by changing the bias voltage of the LC layer from 0 V to 12 V. Furthermore, the absorber is polarization independent and a high absorption for a wide range of oblique incidence is achieved. The designed absorber provides a way forward for the realization of tunable metamaterial devices that can be applied in multi-band detection and imaging.

Abstract-Analysis of the thickness dependence of metamaterial absorbers at terahertz frequencies

Guangwu Duan, Jacob Schalch, Xiaoguang Zhao, Jingdi Zhang, Richard D. Averitt, and Xin Zhang

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-3-2242

Metamaterial absorbers typically consist of a metamaterial layer, a dielectric spacer layer, and a metallic ground plane. We have investigated the dependence of the metamaterial absorption maxima on the spacer layer thickness and the reflection coefficient of the metamaterial layer obtained in the absence of the ground plane layer. Specifically, we employ interference theory to obtain an analytical expression for the spacer thickness needed to maximize the absorption at a given frequency. The efficacy of this simple expression is experimentally verified at terahertz frequencies through detailed measurements of the absorption spectra of a series of metamaterials structures with different spacer thicknesses. Using an array of split-ring resonator (SRR) as the metamaterial layer and SU8 as the spacer material we observe that the absorption peaks redshift as the spacer thickness is increased, in excellent agreement with our analysis. Our findings can be applied to guide metamaterial absorber designs and understand the absorption peak frequency shift of sensors based on metamaterial absorbers.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Identifying the perfect absorption of metamaterial absorbers

G. Duan, J. Schalch, X. Zhao, J. Zhang, R. D. Averitt, and X. Zhang

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.97.035128

We present a detailed analysis of the conditions that result in unity absorption in metamaterial absorbers to guide the design and optimization of this important class of functional electromagnetic composites. Multilayer absorbers consisting of a metamaterial layer, dielectric spacer, and ground plane are specifically considered. Using interference theory, the dielectric spacer thickness and resonant frequency for unity absorption can be numerically determined from the functional dependence of the relative phase shift of the total reflection. Further, using transmission line theory in combination with interference theory we obtain analytical expressions for the unity absorption resonance frequency and corresponding spacer layer thickness in terms of the bare resonant frequency of the metamaterial layer and metallic and dielectric losses within the absorber structure. These simple expressions reveal a redshift of the unity absorption frequency with increasing loss that, in turn, necessitates an increase in the thickness of the dielectric spacer. The results of our analysis are experimentally confirmed by performing reflection-based terahertz time-domain spectroscopy on fabricated absorber structures covering a range of dielectric spacer thicknesses with careful control of the loss accomplished through water absorption in a semiporous polyimide dielectric spacer. Our findings can be widely applied to guide the design and optimization of the metamaterial absorbers and sensors.

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Abstract-Terahertz reflection and visible light transmission of ITO films affected by annealing temperature and applied in metamaterial absorber

Zaiying Shi,  

Lixin Song, 

Tao Zhang

https://www.sciencedirect.com/science/article/pii/S0042207X17315476
The ITO film with visible light transparence, and high terahertz (THz) reflectivity is a promising material for the commercial and engineering applications in the THz field. This study investigates the terahertz optical performance and electrical properties of ITO films prepared by DC magnetron sputtering in the presence of oxygen at different annealing temperatures. By comparing the XPS spectra of ITO films before and after the annealing, the doping theory is employed to explain why and how the ratio of Sn⁴⁺/Sn²⁺ can be changed because of annealing, and it is concluded that Sn with low valence (Sn²⁺) can result in a lower visible transmission. In the THz region, the ITO film has high reflectance that observes the Hagen-Rubens (HR) relationship to some extent. According to the HR relation, the THz reflectance of the ITO film is mainly affected by the conductivity which can be controlled by adjusting the annealing temperature and the oxygen flow in the process of preparation. Applying the prepared ITO film with high THz reflectance into our proposed metamaterial absorber, the experimental result proves that the maximum absorptivity of 94.66%. can be achieved at 4.26 THz.

Abstract-Wide-angle broadband terahertz metamaterial absorber with a multilayered heterostructure

Junxing Fan, Dong Xiao, Qiong Wang, Qiang Liu, and Zhengbiao Ouyang

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-56-15-4388&origin=search

In this paper, a wide-angle broadband perfect absorber is composed of a periodical metamaterial heterostructure. The structure is designed according to the concept that the metamaterial absorber’s resonant frequency range can be manipulated by adjusting the filling factor of a bi-insulator heterostructure. The calculated results reveal that the four-layer herostructure has four perfect absorption peaks at the range of the terahertz frequency band. The related absorption bandwidth is 300 GHz and the average absorptivity is 98.6%. At the same time, the structure is insensitive to the incident angle.

© 2017 Optical Society of America

Abstract-Characteristic analysis of a photoexcited metamaterial perfect absorber at terahertz frequencies

Pibin Bing, Shichao Huang, Zhongyang Li, Zhou Yu, Ying Lu, Jianquan Yao

http://www.worldscientific.com/doi/abs/10.1142/S0217984917502074

The absorption characteristics of a photoexcited metamaterial absorber at terahertz frequencies were analyzed in this study. Filling photosensitive semiconductor silicon into the gap between the resonator arms leads to modulation of its electromagnetic response through a pump beam which changes conductivity of silicon. Comparisons of terahertz absorbing properties which were caused by different thicknesses and dielectric constants of polyimide, cell sizes and widths of SRRs, and lengths and conductivities of the photosensitive silicon, were studied by using Finite Difference Time Domain (FDTD) from 0.4 THz to 1.6 THz. The results of this study will facilitate the design and preparation of terahertz modulator, filters and absorbers.

Abstract-Experimental realization of a terahertz all-dielectric metasurface absorber

Xinyu Liu, Kebin Fan, Ilya V. Shadrivov, and Willie J. Padilla

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-1-191

Metamaterial absorbers consisting of metal, metal-dielectric, or dielectric materials have been realized across much of the electromagnetic spectrum and have demonstrated novel properties and applications. However, most absorbers utilize metals and thus are limited in applicability due to their low melting point, high Ohmic loss and high thermal conductivity. Other approaches rely on large dielectric structures and / or a supporting dielectric substrate as a loss mechanism, thereby realizing large absorption volumes. Here we present a terahertz (THz) all dielectric metasurface absorber based on hybrid dielectric waveguide resonances. We tune the metasurface geometry in order to overlap electric and magnetic dipole resonances at the same frequency, thus achieving an experimental absorption of 97.5%. A simulated dielectric metasurface achieves a total absorption coefficient enhancement factor of FT=140, with a small absorption volume. Our experimental results are well described by theory and simulations and not limited to the THz range, but may be extended to microwave, infrared and optical frequencies. The concept of an all-dielectric metasurface absorber offers a new route for control of the emission and absorption of electromagnetic radiation from surfaces with potential applications in energy harvesting, imaging, and sensing.

© 2017 Optical Society of America

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