Query: metamaterial absorber

title: A dual band metamaterial absorber for graphene surface plasmon resonance at terahertz frequency
abstract: In this paper, we present a dual band metamaterial absorber for graphene surface plasmon resonance at terahertz frequency. We use the finite difference time domain (FDTD) method to study the absorption characteristics of the homocentric graphene ring and disk nanostructure. These simulation results show that the change of the geometrical parameters and the substrate thickness of the nanostructure can change the absorption characteristics and the emergence of dual band absorption peaks. Moreover, we study the field distribution of nanodisks with different radius in detail. By changing the Fermi level of graphene, the wavelength of their absorption peaks can be adjusted flexibly. In addition, the proposed dual band absorber also shows a good angle tolerance for both TE and TM polarizations. By calculation the surface filled water (n 1.332) and 25% aqueous glucose solution (n 1.372) for the metamaterial absorber, the sensitivities of mode I and mode II are 5.0 mm/RIU and 15.0 mm/RIU. These research results will have broad application prospects for sensing and spatial light modulators.

title: Triple band perfect metamaterial absorber with good operating angle polarization tolerance based on split ring arrays
abstract: In this paper, a triple band perfect metamaterial absorber based on Cu dielectric Cu triple layer nanostructure is reported. The top metal film structure consists of a ring and four pairs of capacitor plates, which has a frequency selection effect, allowing the absorber to resonate in the near infrared range. Theoretical study shows that the absorption of the three absorption peaks (872.54 nm, 1008.69 nm and 1138.62 nm) are 87.1% 99.9% and 99.6% respectively. The average absorption is 95.53% including two perfect absorption peaks. Changing the structural parameters can affect its absorption peaks and resonant wavelengths. At the same time, due to the high symmetry of the absorber, it is not sensitive to the polarization angle and incident angle. Whether in the TE mode or the TM mode, the absorber at a wide incident angle (0 60deg) also exhibits good operating angle polarization tolerance. Therefore, the perfect metamaterial absorber we designed can be widely used in sensing.

title: Design of a dual band terahertz metamaterial absorber using two identical square patches for sensing application
abstract: A dual band terahertz metamaterial absorber composed of two identical square metallic patches and an insulating medium layer on top of a continuous metallic ground is demonstrated. Two resonance peaks (labeled A and B) with near 100% absorbance are obtained, of which peak A derived from the localized resonance of the two square patches has a line width of 0.2571 THz and quality factor of 6.9156, while peak B which resulted from the hybrid coupling of the localized resonance of the two square patches and surface lattice resonance of the device has a very narrow line width of 0.0083 THz and large quality factor of 296.2771. Narrow line width and large quality factor have important prospects in sensing application. Based on this, the sensing performance of the device is explored; it is revealed that peak B exhibits highly sensitive sensing ability (including a sensing sensitivity of 1.9010 THz per RIU and figure of merit of 229.04) in terms of the surrounding index. In addition, the influence of structural parameters on the absorption performance is discussed to further verify the formation mechanism of these two absorption peaks.

title: A Tunable Triple Band Near Infrared Metamaterial Absorber Based on Au Nano Cuboids Array
abstract: In this article, we present a design for a triple band tunable metamaterial absorber with an Au nano cuboids array, and undertake numerical research about its optical properties and local electromagnetic field enhancement. The proposed structure is investigated by the finite difference time domain (FDTD) method, and we find that it has triple band tunable perfect absorption peaks in the near infrared band (1000 2500 nm) We investigate some of structure parameters that influence the fields of surface plasmons (SP) resonances of the nano array structure. By adjusting the relevant structural parameters, we can accomplish the regulation of the surface plasmons resonance (SPR) peaks. In addition, the triple band resonant wavelength of the absorber has good operational angle polarization tolerance. We believe that the excellent properties of our designed absorber have promising applications in plasma enhanced photovoltaic, optical absorption switching and infrared modulator optical communication.

title: Dual band tunable terahertz perfect metamaterial absorber based on strontium titanate (STO) resonator structure
abstract: A temperature controlled dual band terahertz perfect metamaterial absorber (MMA) based on strontium titanate (STO) resonator structure is proposed and investigated numerically. This MMA is a simple periodic array, consisting of two stacked square shaped STO resonator structures and a copper substrate. Numerical simulation results indicate that the reflectance of the proposed MMA under room temperature T 300 K is decreased to 2.1% and 0.2% at 0.114 THz and 0.181 THz, and corresponding absorbance is up to 97.9% and 99.8 respectively. Further results show that the designed MMA is polarization insensitive, and wide angle to the incident waves for both transverse electric (TE) and transverse magnetic (TM) modes. The simulated distributions of electromagnetic (EM) fields and power flow reveal that the observed high level absorption is originated from the excitations of the fundamental dipole modes. Furthermore, the absorption property can be changed by varying structural parameters of the MMA and external temperature. Due to its excellent performance, the designed tunable MMA may find useful and important applications such as thermal emitter, bolometric imaging, energy harvesting, and sensing in terahertz region.

title: A Broadband Tunable Terahertz Metamaterial Absorber Based on Single Layer Complementary Gammadion Shaped Graphene
abstract: We present a simple design of a broadband tunable metamaterial absorber (MMA) in the terahertz (THz) region, which consists of a single layer complementary gammadion shaped (CGS) graphene sheet and a polydimethylsiloxane (PDMS) dielectric substrate placed on a continuous metal film. The Fermi energy level (Ef) of the graphene can be modulated dynamically by the applied DC bias voltage, which enables us to electrically control the absorption performance of the proposed MMA flexibly. When Ef 0.8 eV, the relative bandwidth of the proposed MMA, which represents the frequency region of absorption beyond 90% can reaches its maximal value of 72.1% Simulated electric field distributions reveal that the broadband absorption mainly originates from the excitation of surface plasmon polaritons (SPPs) on the CGS graphene sheet. Furthermore, the proposed MMA is polarization insensitive and has wide angles for both transverse electric (TE) and transverse magnetic (TM) waves in the broadband frequency range. The broadband absorption capacity of the designed MMA can be effectively adjusted by varying the Fermi energy level of graphene. Lastly, the absorbance of the MMA can be adjusted from 42% to 99.1% by changing the Ef from 0 eV to 0.8 eV, which is in agreement with the theoretical calculation by using the interference 41theory. Due to its simple structure and flexible tunability, the proposed MMA has potential application prospects in tunable filtering, modulators, sensing, and other multispectral devices.

title: Study on Temperature Adjustable Terahertz Metamaterial Absorber Based on Vanadium Dioxide
abstract: In the study of modern optics, the work of terahertz metamaterial absorbers is mostly multi band perfect absorbers and ultra wideband perfect absorbers. In contrast, in practical applications, metamaterial absorbers with adjustable resonance frequency or amplitude play an essential role in many forms. Here, we firstly designed an ultra wideband terahertz metamaterial perfect absorber, achieving over 99% perfect absorption in the 6.6 8.9 THz range. Secondly, based on the absorber, phase change material VO2 was added to improve the structure, and three tunable terahertz metamaterial absorbers based on VO2 were designed, respectively realizing broadband movement and conversion between broadband and multi band. Also, the terahertz absorber with dynamic tuning characteristics can flexibly control the absorption performance, providing an excellent platform for the realization of terahertz filtering, modulation, and so on.

title: Elliptical metallic rings shaped fractal metamaterial absorber in the visible regime
abstract: Achieving the broadband response of metamaterial absorbers has been quite challenging due to the inherent bandwidth limitations. Herein, the investigation was made of a unique kind of visible light metamaterial absorber comprising elliptical rings shaped fractal metasurface using tungsten metal. It was found that the proposed absorber exhibits average absorption of over 90% in the visible wavelength span of 400 750 nm. The features of perfect absorption could be observed because of the localized surface plasmon resonance that causes impedance matching. Moreover, in the context of optoelectronic applications, the absorber yields absorbance up to 70% even with the incidence obliquity in the range of 0deg 60deg for transverse electric polarization. The theory of multiple reflections was employed to further verify the performance of the absorber. The obtained theoretical results were found to be in close agreement with the simulation results. In order to optimize the results, the performance was analyzed in terms of the figure of merit and operating bandwidth. Significant amount of absorption in the entire visible span, wide angle stability, and utilization of low cost metal make the proposed absorber suitable in varieties of photonics applications, in particular photovoltaics, thermal emitters and sensors.

title: Perfect metamaterial absorber.
abstract: We present the design for an absorbing metamaterial (MM) with near unity absorbance A(omega) Our structure consists of two MM resonators that couple separately to electric and magnetic fields so as to absorb all incident radiation within a single unit cell layer. We fabricate, characterize, and analyze a MM absorber with a slightly lower predicted A(omega) of 96% Unlike conventional absorbers, our MM consists solely of metallic elements. The substrate can therefore be optimized for other parameters of interest. We experimentally demonstrate a peak A(omega) greater than 88% at 11.5 GHz.

title: High Quality Factor, High Sensitivity Metamaterial Graphene Perfect Absorber Based on Critical Coupling Theory and Impedance Matching
abstract: By means of critical coupling and impedance matching theory, we have numerically simulated the perfect absorption of monolayer graphene. Through the critical coupling effect and impedance matching, we studied a perfect single band absorption of the monolayer graphene and obtained high quality factor (Q factor 664.2) absorption spectrum which has an absorbance close to 100% in the near infrared region. The position of the absorption spectrum can be adjusted by changing the ratio between the radii of the elliptic cylinder air hole and the structural period. The sensitivity of the absorber can be achieved S 342.7 nm/RIU (RIU is the per refractive index unit) and FOM 199.2 (FOM is the figure of merit) which has great potential for development on biosensors. We believe that our research will have good application prospects in graphene photonic devices and optoelectronic devices.