A simple design of a broadband multifunctional polarization converter using an anisotropic metasurface for X-band application is proposed. The proposed polarization converter consists of a periodic ...array of the two-corner-cut square patch resonators based on the FR-4 substrate that achieves both cross-polarization and linear-to-circular polarization conversions. The simulated results show that the polarization converter displays the linear cross-polarization conversion in the frequency range from 8 to 12 GHz with the polarization conversion efficiency above 90%. The efficiency is kept higher than 80% with wide incident angle up to 45°. Moreover, the proposed design achieves the linear-to-circular polarization conversion at two frequency bands of 7.42-7.6 GHz and 13-13.56 GHz. A prototype of the proposed polarization converter is fabricated and measured, showing a good agreement between the measured and simulated results. The proposed polarization converter exhibits excellent performances such as simple structure, multifunctional property, and large cost-efficient bandwidth and wide incident angle insensitivity in the linear cross polarization conversion, which can be useful for X-band applications. Furthermore, this structure can be extended to design broadband polarization converters in other frequency bands.
In this paper, a broadband metamaterial microwave absorber is designed, simulated and measured. Differently from the traditional method which is only based on unit cell boundary conditions, we ...carried out full-wave finite integration simulations using full-sized configurations. Starting from an elementary unit cell structure, four kinds of coding metamaterial blocks, 2 × 2, 3 × 3, 4 × 4 and 6 × 6 blocks were optimized and then used as building blocks (meta-block) for the construction of numerous 12 × 12 topologies with a realistic size scale. We found the broadband absorption response in the frequency range 16 GHz to 33 GHz, in good agreement with the equivalent medium theory prediction and experimental observation. Considering various applications of metamaterials or metamaterial absorbers in the electromagnetic wave processing, including the radars or satellite communications, requires the frequency in the range up to 40 GHz. Our study could be useful to guide experimental work. Furthermore, compared to the straightforward approach that represents the metamaterials configurations as 12 × 12 matrices of random binary bits (0 and 1), our new approach achieves significant gains in the broadband absorption. Our method also may be applied to the full-sized structures with arbitrary dimensions, and thus provide a useful tool in the design of metamaterials with specific desired frequency ranges.
Developing a simple structure using low-cost material that enables both large-scale fabrication and broadband absorption response is highly desirable but very challenging for achieving ...high-performance metamaterial absorber. Herein, we propose and numerically investigate an ultra-broadband and wide-angle insensitive perfect metamaterial absorber in the ultraviolet to near-infrared (UV–NIR) region based on a simple metal–dielectric–metal structure. The proposed absorber structure consists of a periodic array of a tungsten hexagonal prism and a tungsten ground plane separated by a silicon dioxide dielectric substrate. The proposed absorber achieves an ultra-broadband absorption response in the range of 275–1000 nm with an absorptivity above 90
%
and a relative bandwidth of 106.8
%
at normal incidence, which covers from the UV to NIR region. The absorption efficiency is maintained with the figure of merit
η
OBW
higher than 90
%
for a wide incident angle up to 40
o
for transverse electric (TE) polarization and 65
o
for transverse magnetic (TM) polarization. The effects of structural parameters and different metallic materials on the absorption performance are presented. In addition, the physical mechanism is analyzed using the surface density and distributions of electric and magnetic fields that are attributed to both localized surface plasmon (LSP) and propagating surface plasmon (PSP) resonances. Owing to outstanding merits of simple structure, low cost, and high absorption performance, the designed absorber can be suitable for many applications in the UV–NIR spectrum such as thermal emitters and solar cells.
Fluorescence imaging is an important technique used for early diagnosis and effective treatment of some incurable diseases including cancer. Herein, we report novel NaYF4:Yb3+/Er3+@silica-TPGS ...bio-nano complexes for labeling cancer cells. The NaYF4:Yb3+/Er3+ nanoparticles have been successfully synthesized via a hydrothermal route, further coated with a silica shell, and functionalized with d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS). The experimental results indicate that NaYF4:Yb3+/Er3+@silica-TPGS emits stronger upconversion luminescence than NaYF4:Yb3+/Er3+ under an excitation of 980 nm. More significantly, the NaYF4:Yb3+/Er3+@silica-TPGS bio-nano complexes could strongly label MCF-7 breast cancer cells for in vitro experiments detected by a fluorescence microscope. On the other hand, the complex could not typically probe healthy cells, which are HEK-293A human embryonic kidney cells, under the same experimental conditions. Because of their strong upconversion luminescence, good dispersibility, and biocompatibility, NaYF4:Yb3+/Er3+@silica-TPGS bio-nano complexes can be a promising candidate/probe for biomedical labeling and diagnostics.
The design of a lightweight and ultra‐wideband absorber for C and X bands is still a challenge as the dimension of the absorber is relatively large in such a relatively low‐frequency band. Herein, an ...ultra‐wideband and lightweight metamaterial absorber (MMA) is presented for C‐ and X‐band applications. The unit cell of the proposed MMA consists of four copper sectors loaded by lumped resistors and a continuous copper ground plane, which is printed on two FR‐4 substrates. Furthermore, an airgap separating the FR‐4 layers is used as the active substrate medium of the MMA to achieve both ultra‐wideband absorption spectra and lightweight design. The MMA is investigated by simulation and measurement, showing that a good agreement is achieved. The result indicates that the absorptivity of the MMA under both transverse electric (TE) and transverse magnetic (TM) polarizations is greater than 90% in a wide range from 3.7 to 13.6 GHz for all polarization angles. Compared to other reported broadband absorbers, the proposed MMA shows an ultra‐wide absorption bandwidth and a lightweight design, which demonstrates a great potential for C‐and X‐band applications.
Herein, a lightweight, ultra‐wideband, and polarization‐insensitive metamaterial absorber is designed and fabricated. The designed absorber exhibits absorption response with absorptivity greater than 90% in a wide range from 3.7 to 13.6 GHz and a relative bandwidth of 114.5% for all polarization angles, which entirely covers both the C and X bands.
We numerically and experimentally investigated the metamaterial absorber (MMA) based on ring and dish structures in GHz region. It found that the combined structure of ring and dish (RD) exhibit ...dual-band absorption peaks at 8.6 and 15.6GHz. By replacing the ring to the structure of split-ring and dish (SRD), the first magnetic resonance peak is shifted from 8.6 to 14.0GHz. The physical mechanism of magnetic resonance frequencies was elucidated using simple LC circuit model. We achieved a broadband MMA with bandwidth of 3.7GHz by arranging four SRD structures into a super unit-cell. The experimental results are good agreement with both the numerical simulation and calculation.
We numerically and experimentally investigate single-band and dual-band isotropic metamaterial absorbers (IMAs) based on metallic disks. By optimizing the diameter of the metallic disks and the ...thickness of the dielectric substrate, the single-band IMA is observed at 16.2 GHz with absorptivity of 97%. When adding one disk-pair to the structure, the dual-band IMA is obtained at 12.8 and 15.5 GHz due to the symmetry breaking. The physical mechanics is explained by near-field coupling effect and equivalent LC circuit model. The measurement results performed in the range 12–18 GHz show a good agreement with simulation and theoretical analysis. Our findings demonstrate a new approach to achieve dual-band and multi-band IMAs.
•Single-band and dual-band isotropic metamaterial absorbers (IMAs) based on disk resonators.•Single-band and dual-band IMAs are obtained by asymmetric structure and near-field coupling effect.•Dual-band and multi-band can be adjusted by the thickness of dielectric layer and the diameter of metallic disks.•A new simple and effective approach to achieve dual-band and multi-band IMAs.
Metamaterial full-sized absorber structures are numerically and experimentally investigated in GHz region and then examined in THz frequency. By manipulating monitoring the number and the position of ...the defect elements in conventional unit cells, the optimal integrative absorber structures are generated. The proposed structures provide an ultra-broadband absorbance in the operating frequency. The good agreement between simulation, measurement and theoretical analysis is observed with a 5 GHz-bandwidth corresponding to the absorption of 95%. In particular, we extrapolate the concept to THz region and demonstrate that, the method can be applied to increase the bandwidth of the metamaterial absorber to 5 THz, while maintaining the other characteristics. This structure can be applied to improve the performance of telecommunication systems such as micro-antenna, micro-electromagnetic transmitters and apply to imaging and sensing fields.
Polarization-control devices have attracted considerable interest, however, most of the polarization converters operating at lower frequencies have a heavy design and narrow bandwidth which limits ...their practical applications. Here we report a simple design of an ultra-wideband and lightweight polarization converter for applications in the S- and C-bands. The proposed converter is designed based on a metasurface structure with the dielectric layer modified to hollow structure to obtain a lightweight design even working at such low frequency. Theoretical analysis and simulation results indicate that the converter can convert the orthogonal polarization transformation of reflected wave. Furthermore, the measurement results show good agreement with the simulation results. The proposed polarization converter can achieve a polarization conversion ratio above 90% in an ultra-wide frequency range from 2 to 8.45 GHz due to multi-resonance modes. These performances are going beyond state of the art in terms of bandwidth and lightweight design, thus it can be applied in various applications in the operating bands.
We numerically and experimentally investigate a broadband, polarization-independent and wide-incident-angle metamaterial perfect absorber (MPA) based on conductive polymer. By optimizing the ...electrical conductivity of the polymer, a 16.7 GHz broadband MPA is observed with the absorptivity greater than 80% for both transverse magnetic and electric polarization. The measurement results performed in the range 8-18 GHz show a diametrical concatenation with simulation results and theoretical analysis. The absorption mechanism is explained by demonstrating the influence of polymer conductivity on the dissipated power, the equivalent impedance, and the induced electric field. Our work may contribute to further studies on broadband MPA using for various applications.
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