Absorbers have high potential application values in the military field, such as electronic screening, radar cross-section reduction and invisible cloaking. However, most methods have the defects of narrow bandwidth, low absorptivity, complex three-dimensional structure and fixed polarizations. In this paper, we realize an ultra-broadband and full-polarization planar metamaterial absorber (PMA) with a three-layer composite structure, which exhibits multi-resonant and impedance matching properties by combining the ultra-light foams and indium tin oxide (ITO) films. The bottom two layers achieve a high-efficiency absorption rate at the low and medium spectrum, while the upper layer realizes a absorption property at a high frequency. Also, an equivalent circuit model is extracted to explain its operating mechanism. The experimental results show that our meta-absorber can achieve great absorber performance of better than 90% within 1-18 GHz for full-polarization incident waves, which is in great agreement with the numerical simulations. Moreover, our device is insensitive to oblique incidences and polarizations and possesses the physical characteristics of an ultralight, weighing 0.6 kg for a square meter, which is only 1/85.0-1/126.7 of the conventional absorbers under the same size. All these excellent performances determine that our research can be a good candidate for military stealth materials.

Wavefront manipulation is of great importance in the development of science and technology, and the generation of vortex beam is one of the most effective methods to improve the channel capacity and communication accuracy. However, current available vortex beam generators suffer from complex structure, large size, especially narrow bandwidth. To solve these issues, we propose a general strategy to enhance the bandwidth of the vortex beam generator by using double-layered reflective metasurface. The well-optimized double-layered reflective element possesses dual resonance, which realizes complete phase coverage (larger than 360 degrees) and a flat slope of the reflection phase, resulting in a broad bandwidth (8.5-11.5GHz). A compact and low-profile vortex-beam generator is proposed by combining the parabolic phase and the spiral phase plate phase. Both near field and far field experiments are performed to demonstrate the predesigned effects. A pure vortex beam is observed clearly with a topological charge of m=1 in a wide frequency window of 3 GHz (8.5-11.5GHz). More importantly, the working efficiency of the vortex beam is better than 90% at center frequency 10 GHz. The findings in this paper motivate the realization of high-performance reflective metasurfaces and other functional metadevices.

Perfect absorbers are highly desired in many engineering and military applications, including radar cross section (RCS) reduction, cloaking devices, and sensor detectors. However, most types of present absorbers can only absorb space propagation waves, but absorption for surface waves has not been researched intensively. Surface waves are easily excited on the interfaces between metal and dielectrics for electronic devices, which decreases their working performances due to the electromagnetic disturbances. Thus, it is of great significance to design appropriate absorbers to dissipate undesirable surface waves. Here, we propose the concept of a surface wave absorber, analyze its working principle, and prove its good performances experimentally. To demonstrate our concept, we design and fabricate a realistic surface wave absorber that is fixed on a metal surface. Experiments are performed to verify its electromagnetic characteristics. The results show that our designed meta-absorber can achieve an excellent surface wave absorption within a wide frequency window (5.8–11.2 GHz) and exhibit a very high efficiency over than 90%, but only with the thickness of 1 mm (0.028 λ). Our device can help to solve the issues of absorption at large angles, and it can find wide applications in large antenna array design and other communication systems.

Terahertz (THz) meta-devices are considered to be a promising framework for constructing integrated photonic circuitry, which is significant for processing the upsurge of data brought about by next-generation telecommunications. However, present active metasurfaces are typically restricted by a single external driving field, a single modulated frequency, fixed switching speed, and deficiency in logical operation functions which prevents devices from further practical applications. Here, to overcome these limitations, we propose a hybrid THz metasurface consisting of vanadium dioxide (VO₂) and germanium (Ge) that enables electrical and optical tuning methods individually or simultaneously and theoretically investigate its performance. Each of the two materials is arranged in the meta-atom to dominate the resonance strength of toroidal or magnetic dipoles. Controlled by either or both of the external excitations, the device can switch on or off at four different frequencies, possessing two temporal degrees of freedom in terms of manipulation when considering the nonvolatility of VO₂ and ultrafast photogenerated carriers of Ge. Furthermore, the “AND” and “OR” logic operations are respectively achieved at two adjacent frequency bands by weighing normalized transmission amplitude. This work may provide an auspicious paradigm of THz components, such as dynamic filters, multiband switches, and logical modulators, potentially promoting the design and implementation of multifunctional electro-optical devices in future THz computing and communication.

A novel ultracompact two‐dimensional (2D) waveguide‐based metasurface is proposed herein and applied for the first time to reduce mutual coupling in antenna array for multiple‐input multiple‐output applications. The unit cell of the proposed 2D waveguide‐based metasurface is ultracompact (8.6 mm × 4.8 mm, equal to λ₀/14.2 × λ₀/25.5) mainly due to the symmetrical spiral lines etched on the ground. The metasurface exhibits a bandgap with two transmission zeros attributing to the negative permeability in the vicinity of magnetic resonance and the negative permittivity in the vicinity of electric resonance. Taking advantage of these two features, a microstrip antenna array is then designed, fabricated, and measured by embedding an 8 × 1 array of the well‐engineered 2D waveguide‐based metasurface elements between two closely spaced (9.2 mm, equal to λ₀/13.3) H‐plane coupled rectangular patches. There is good agreement between the simulated and measured results, indicating that the metasurface effectively reduces antenna mutual coupling by more than 11.18 dB and improves forward gain. The proposed compact structure has one of the highest reported decoupling efficiencies among similar periodic structures with comparable dimensions. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:789–794, 2015.

In this paper, we proposed a three-dimensional (3D) metamaterial absorber joint by lightweight 3D grid structure and traditional magnetic materials, which can achieve wideband and wide-angle perfect absorption at 5–20 GHz. By simulation, the broadband absorption remained almost 90% from 0° to 80° for TM wave. The surface current and power loss distributions were investigated to interpret the physical mechanism of wideband and wide-angle absorption. The broadband and wide-angle absorption were derived from magnetic and electric resonances between the top resistive film, background plane and magnetic loss of magnetic materials. The results proved that different layers of the proposed absorber play different loss roles, and finally contributed to the wideband and wide-angle absorption. The polarization insensitive stability of the proposed absorber was also demonstrated at different polarized angles. The present study provided a new design to achieve a polarization insensitive, wideband and wide-angle absorber. Moreover, the structure absorber has potential applications in other fields, including the solar cell, imaging and detection etc.