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.

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 σ_si = 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.

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.

A mechanically controlled switchable wideband frequency–selective rasorber/absorber, with the transmission window inside the absorption band, based on a frequency–selective surface and a rotatable metal plate, is presented in this paper. The absorption of the switchable rasorber/absorber is over 90%, from 3.9 GHz to 11.77 GHz, when the rotatable metal plate is parallel to the rest of the layers, and its transmission coefficient can reach up to 0.62 at 11.6 GHz, with the rotatable metal plate perpendicular to the rest of the layers. The mechanism of wideband absorption and transmission are explained by monitoring and analyzing the surface current distribution at the absorption and transmission frequencies. The control method is simple, reliable and accurate. It has application value in communication and radar stations.