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Tailoring absorption spectrum by inserting an epsilon-near-zero film into metal-dielectric-metal assembly
摘要： A method of tailoring the absorption band generated by metal-dielectric-metal (MDM) resonator is analytically proposed and numerically investigated in this paper. By inserting an epsilon-near-zero (ENZ) ?lm into the MDM layers, the absorption bandwidth can be su?ciently widened due to the coupling from ENZ mode to localized edge plasmon mode. Theoretical instructions of how to design respective layer thickness to obtain optimized absorption rate are investigated with the guidance of vast simulations and the hybrid resonance characteristics by the coupling from ENZ mode are further inspected by monitoring the resonant electric and magnetic ?eld. The meta-absorber can achieve high absorption with a large bandwidth under oblique incidence. The method and the structure proposed in this paper have potential views in highly integrated nanostructures in solar cells, photovoltaic and sensing application ?elds.
关键词： Epsilon-near-zero (ENZ),Absorber,Metamaterial
更新于2025-09-23 15:19:57
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[IEEE 2018 18th Mediterranean Microwave Symposium (MMS) - Istanbul, Turkey (2018.10.31-2018.11.2)] 2018 18th Mediterranean Microwave Symposium (MMS) - Polarization Insensitive Metamaterial Absorber Using Sunflower Shaped Unit Cell
摘要： In this paper, a novel polarization insensitive metamaterial absorber using sunflower shaped unit cell is proposed. The performance of the proposed absorber was demonstrated with 3D full-wave EM solver under normal incidence for TE and TM polarization modes. Due to the symmetric geometry of the sunflower shaped unit cell, the proposed absorber provides a high level of absorptivity, about %90, for both TE and TM modes at 11.9 GHz. To enhance the absorptivity, we then created a hollow at the center of the proposed unit cell. The later device resonates at 11.7 GHz, and provides perfect absorption for both polarization modes. Our study reveals that employing hollow type symmetrical gaps provokes the interaction of EM wave and the metamaterial, and can lead to the perfect metamaterials for X-band absorber applications.
关键词： Metamaterial,absorber,X band,unit cell,polarization insensitive
更新于2025-09-19 17:15:36
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Superconducting Filter Based on Split Ring Resonator Structures
摘要： A design of high-temperature superconducting (HTS) bandpass filter (BPF) based on split ring resonator (SRR) structures is presented in this paper. The SRR has been considered as a classical element for metamaterials and exhibits characteristics of subwavelength resonator, hence can aid in the compact design of filters. Filter has been simulated and optimized using Sonnet software. The measured results of the filter have good consistency with the simulated results and show good band pass characteristics. The center frequency of the filter measured at 70K was 2.515GHz, the rectangle coefficient was 1.22, and the insertion loss was 0.1dB at the center frequency.
关键词： high-temperature superconducting,bandpass filter,split ring resonator,metamaterial
更新于2025-09-19 17:15:36
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[IEEE 2018 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting - Boston, MA, USA (2018.7.8-2018.7.13)] 2018 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting - Computational Millimeter-wave Spotlight Imaging using Holographic Metasurface Antennas
摘要： In this paper, a spotlight imaging system integrated with a frequency-diverse aperture is presented for security-screening applications. The spotlight imager consists of holographic metasurface antennas that can dynamically be tuned to radiate spotlight patterns allowing the extraction of high-resolution images from a constrained field-of-view (FOV). The spotlight aperture operates at a single frequency, 75 GHz, within the W-band frequency regime (75 – 110 GHz) and is used for the identification of threat objects while the frequency-diverse aperture operates at K-band frequencies (17.5 – 26.5 GHz) and is used for detection purposes, determining the constrained FOV to be imaged using the spotlight imager at high resolution.
关键词： spotlight,metamaterial,metasurface,millimeter-wave,microwaves,imaging,focusing
更新于2025-09-19 17:15:36
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Enhanced Conversion Process in a Sub-wavelength Thin Upconversion Layer by Using Metamaterial Mirror
摘要： Because of finite bandgap, useful spectral ranges of semiconductors are limited for photovoltaic applications. The upconversion (UC) process is one of alternatives to extend the useful spectral range by converting long wavelength photons to short wavelength photons. For example, NaYF4 codoped Yb3+/Er3+ converts photons from near-infrared (970 nm) to visible (660 nm). However, in the form of a thin layer on a flat metal mirror, which is a representative structure to add UC layer into photovoltaic devices, the UC material exhibits low efficiency in optical devices because of its low absorption and conversion efficiencies. In this paper, the UC process is highly enhanced by a metamaterial mirror consisting of grooved silver surfaces. The absorption of UC material is improved by a factor of 5.3 due to increased light-matter interaction because the electric field is highly concentrated in the UC layer near the metal surface. The surface plasmon polariton (SPP) modes induced by a dipole emitter to a metal grooved surface enhance the spontaneous emission (SE) rate of the emission wavelength of UC material by a factor of 65 compared with a thin UC layer on flat mirror. Consequently, total efficiency of the UC process is 400 times more enhanced than the reference structure by magnetic mirror property and SPP modes of metamaterial mirror.
关键词： Metamaterial,Upconversion,Thin film
更新于2025-09-19 17:15:36
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[IEEE 2018 18th Mediterranean Microwave Symposium (MMS) - Istanbul, Turkey (2018.10.31-2018.11.2)] 2018 18th Mediterranean Microwave Symposium (MMS) - Chiral SRR Metasurfaces for Circular Polarisation Conversion
摘要： A circular polarization dual band metamaterial polarization rotator composed of two double split ring resonators rotated 90o with respect to each other is presented. Asymmetric transmission between Txx and Tyy and symmetric transmission between Txy and Tyx has been achieved. The circular polarization is caused by the symmetric transmission between Txy and Tyx. The design has been demonstrated numerically at microwaves frequency. The structure holds promise for ultra-compact polarizing devices for any frequency range given the scalability of the approach.
关键词： Metasurfaces,Circular polarization,Chiral metamaterial,Split Ring Resonators
更新于2025-09-19 17:15:36
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Implementing infrared metamaterial perfect absorbers using dispersive dielectric spacers
摘要： A typical metamaterial perfect absorber (MPA) is comprised of a metamaterial layer, a dielectric spacer, and a ground plane. The conventional spacer material is usually a lossy dielectric with little-dispersion for the purpose of easing the design and optimization procedure of the MPA. In this paper, we present the design, fabrication, and characterization of metamaterial perfect absorbers with a highly dispersive spacer, which is compatible with functional microelectromechanical systems. The measured dispersive permittivity of a silicon nitride thin film is used in modeling the absorption response of MPAs with rigorous coupled wave analysis. Different designs of MPA structures are fabricated and characterized. Spectroscopy data shows two perfect absorption peaks in wavelengths ranging from 8 μm to 20 μm, which supports the theoretical calculation and numerical simulation. The dispersion of silicon nitride enables the shared resonant modes of the two peak wavelengths and decreases the wavelength shift led by variations in structural parameters. We demonstrate that the use of dispersive dielectric materials in MPAs potentiates various functional devices.
关键词： rigorous coupled wave analysis,metamaterial perfect absorber,infrared,silicon nitride,fabrication,characterization,dispersive dielectric
更新于2025-09-19 17:15:36
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Ultra-narrow band perfect metamaterial absorber based on dielectric-metal periodic configuration
摘要： The ultra-narrow band perfect metamaterial absorber (PMA) based on dielectric-metal periodic configuration for near infrared spectral region is proposed. The PMA consists of a dielectric resonant structure and a metal substrate. Two design examples show that the proposed PMAs are able to exhibit nonpolarizing absorption peaks at normal and oblique incidences respectively. Moreover, the absorption spectra of the PMA for oblique incidence are insensitive to the incident angle under TE polarized light illumination. But this PMA exhibits a large spectral shift by rotating the angle of incidence under TM polarized light illumination. Then a PMA sample for oblique incidence is fabricated through thin-film deposition and electron beam lithography patterning. Finally, the reflection spectra of the fabricated PMA sample are measured. The absorption spectra obtained by subtracting the measured reflection spectra from incident spectra are consistent with the theory. Thus the novel characteristics of the ultra-narrow band PMA based on dielectric-metal periodic configuration are experimentally demonstrated.
关键词： Ultra-narrow band,Nonpolarizing absorption,Perfect metamaterial absorber,Tunable spectrum,Diffraction grating
更新于2025-09-19 17:15:36
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Design and equivalent circuit model extraction of a third-order band-pass frequency selective surface filter for terahertz applications
摘要： In this paper, a third-order band-pass frequency selective surface (FSS) filter is proposed for terahertz applications. The presented FSS filter is designed based on miniaturized unit cells and a fractional bandwidth of 72% around 0.775 THz is achieved. In addition, a high transmission magnitude is obtained with an acceptable flatness in comparison to previous reports. In order to verify the numerical results, an equivalent circuit model of the proposed spatial filter is introduced considering both normal and oblique incident angles. The sensitivity of the filter with respect to the incident wave angle is investigated in the range of 0–60° whereas the obtained performance is acceptable for various incident angles in the mentioned range. Moreover, the effects of altering different geometrical parameters are studied and justified based on the extracted equivalent circuit model.
关键词： Miniaturized elements,Terahertz filter,Equivalent circuit model,Metamaterial,Frequency selective surface
更新于2025-09-19 17:15:36
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Graphene-enabled tunable multifunctional metamaterial for dynamical polarization manipulation of broadband terahertz wave
摘要： Graphene-enabled metamaterials have emerged as promising photoelectric devices for dynamically controlling the polarization of electromagnetic waves. However, it is still a key technological challenge to design a tunable metamaterial possessing more sufficient freedom for polarization manipulation. Here, we propose a graphene-enabled tunable multifunctional metamaterial consisting of metallic strips arranged on a grounded polymer substrate embedded with a graphene sandwich structure to electrically control the polarization states of terahertz waves. By adjusting the Fermi energy of graphene through voltage biasing, the electromagnetic responses of the presented metamaterial can be tailored, resulting in dynamical tunable polarization manipulation in reflection mode. All expected performances are demonstrated through full wave simulation. The results reveal that this metamaterial device can operate as a switchable quarter-wave plate and a tunable half-wave plate for both linear- and circular-polarization incidences. Furthermore, the polarization conversion ratio, of which incident waves are converted to their cross-polarized reflection mode, can be continuously regulated from 2% to 95% in a wide band from 1.46 to 2.26 THz. The proposed metamaterial continues the process of developing tunable polarizers and polarization switchers with graphene materials, and may be applied in various areas such as wireless communication, terahertz sensing and imaging.
关键词： Polarization manipulation,Terahertz,Graphene,Tunable,Metamaterial
更新于2025-09-19 17:13:59