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We present an optically reconfigurable multifunctional metamaterial with switchable wideband absorption and transmission across the THz frequency range. The reconfigurability is achieved by introducing optically active silicon into the resonator of the metamaterial unit which could be effectively modulated through external electrical pumping. When the silicon conductivity reaches 50,000 S/m, the metamaterial shows significant absorption of electromagnetic waves ranging from 3.1 to 10 THz. By reducing the applied external pump power and decreasing the silicon conductivity to 150 S/m, the proposed metamaterial exhibits transmission of the incident waves at 5.12 THz with a transmission coefficient of 61%. The proposed optically reconfigurable metamaterial has the advantages of simple structure, wideband absorption, and switchable between absorption and transmission modes, showing potential applications in stealth, communication, or radar systems. [ABSTRACT FROM AUTHOR]

This paper proposes a thermally controlled multifunctional metamaterial absorber with switchable wideband absorption and transmission at the THz band based on resistive film and vanadium dioxide (VO2). The function of the absorber can be adjusted by changing the phase transition characteristics of VO2. When VO2 is in a metallic state, the absorber can achieve wideband absorption with above 90% absorption from 3.31 THz to 10 THz and exhibits excellent absorption performance under a wide range of incident and polarization angles. When VO2 is in an insulating state, the metamaterial acts in transmission mode with a transmission coefficient of up to 61% at 5.15 THz. The transmission region is inside the absorption band, which is very important for practical applications. It has the advantages of having a simple structure, wideband absorption, and switchable absorption/transmission with potential application value in the fields of stealth of communication equipment and radar at the THz band. [ABSTRACT FROM AUTHOR]

Based on the tunable conductivity of silicon as a function of incident pump power, a photoexcited switchable dual-function metamaterial absorber for sensing and wideband absorption at the THz band is designed in this paper. The absorber has an absorption peak at 2.08 THz with the absorption up to 99.6% when the conductivity of silicon is 150 Sm−1, which can be used for sensing. The refractive index sensitivity of the absorption peak is up to 456 GHz/RIU. A wideband absorption is generated from 3.4 THz to 4.5 THz with the bandwidth of 1.1 THz as the conductivity σsi = 12,000 Sm−1. The generation mechanism of the sensing absorption peak and wideband absorption is explained by monitoring the surface current, electric, and magnetic field distribution at some absorption frequencies. It has the advantages of being simple and having a high sensitivity, and wideband absorption with wide application prospects on terahertz communication, electromagnetic stealth, and biochemical detection. [ABSTRACT FROM AUTHOR]

Acoustic metasurfaces based on microperforated panels and coplanar spiral tubes are proposed to realize acoustic absorption in the low‐frequency range, which are composed of holes and an in‐plane coiling‐up channels. Herein, the deep‐subwavelength metasurfaces are developed based on nesting damping subchannels for dual‐band or broadband acoustic absorption in the low‐frequency regime. The absorption properties of the proposed metasurfaces are theoretically and experimentally studied. At the resonant frequencies, high acoustic absorption is observed at deep‐subwavelength scale (the thickness of metasurfaces is smaller than λ/50). The measured results show that both dual‐band and broadband metasurface‐based acoustic absorbers are realized at around 300 Hz, in good agreement with theoretical predictions by properly designing the profile of the holes and channels. Furthermore, the measured acoustic impedances are presented as effectual quantity revealing the dual‐band and broadband feature of the metasurface absorbers. The design herein can be further applied to extra broadband absorption with a compact metasurface in future. [ABSTRACT FROM AUTHOR]

Graphical abstract This work not only exhibits the importance of interfacial polarization in EM wave absorbing process, but also demonstrates that the incident angle of EM wave plays an important role in EM wave absorption performance. Abstract Hierarchical chrysanthemum-like CuCo 2 O 4 -CuO composites were successfully synthesized by a facile one-pot hydrothermal method after calcination at 500 °C. Based on the results of X-ray diffraction (XRD), Raman spectra, thermogravimetric analysis (TGA) and transmission electron microscope (TEM), we found that not only the morphology (from 2 dimensional to 3 dimensional) but also the crystalline structure (Cu0 + Cu 2 O + CoO x → CuO + CuCo 2 O 4) of the samples could be tuned by the calcination temperature. The existed interfaces of CuCo 2 O 4 -CuCo 2 O 4 , CuCo 2 O 4 -CuO, and CuO-CuO played a key role on the attenuation of electromagnetic waves. The effective absorption frequency bandwidth is up to 4.02 GHz with a matched thickness of 2.8 mm. The CuCo 2 O 4 -CuO/paraffin composites can even exhibit bigger effective frequency bandwidth (from 4.02 to 4.65 GHz) if we turn the incident angle of electromagnetic (EM) wave to a proper value (i.e. , 45°). We believe that the hierarchical chrysanthemum-like CuCo 2 O 4 -CuO composites can be a good candidate for the high-performance Co-based spinel microwave absorbers. [ABSTRACT FROM AUTHOR]

An optically transparent metamaterial for microwave absorber with wide operation angle, polarization insensitivity, broadband and high absorptivity was demonstrated. The metamaterial is composed of planar indium tin oxide (ITO) structures and low-loss glass substrates. By tailoring the reflection response of ITO patterns and the position of arrayed ITO resonators between quartz glass dielectric substrates, more than 90% absorption in the frequency ranges of 8–20 GHz and within a wide angular range from 0° to 60° is achieved. Meanwhile, by employing transparent substrates, including soda-lime glass and quartz glass, good optical transmittance (80%) is obtained. The dielectric loss of quartz glass is lower than other dielectric substrates, which implies that the high absorptivity was achieved mainly due to the contribution of planar ITO metamaterial structure. The reflectivity of proposed MMAs is simulated and measured experimentally. Both of which demonstrate excellent absorption performance of the metamaterial. The optically transparent broadband metamaterials absorber with high absorptivity and polarization insensitivity opens a horizon of potential applications in many fields. • We report a metamaterial with more than 90% absorption in the whole frequency ranges of 8–20 GHz within a wide angular range from 0° to 60°. • By employing transparent substrates, including soda-lime glass, quartz glass and ITO structures, high optical transmittance (80%) is obtained. • Low-loss optical glass can be employed for high-performance electromagnetic absorber by designing the ITO structures and the position within the substrates. [ABSTRACT FROM AUTHOR]