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.

A graphene-based tunable wideband metamaterial absorber with polarization insensitivity and wide incident angle is presented in this paper. The results show that the absorption is over 90% from 5 to 8 GHz when the Fermi level of graphene is 0.5 eV, and the absorption can be tuned by electrically changing the Fermi level of graphene. The mechanism of wideband and tunable absorption is explained by calculating the normalized input impedance and monitoring the surface current. Finally, the results adequately verify that the absorption of metamaterial absorber has the advantages of polarization insensitivity and wide incident angle. Thus, it holds great potential application value in many fields such as electromagnetic stealth, electromagnetic shielding, communication, and so on.

Graphene has the capability of dynamically tuning its conductivity through gate voltage. Based on this fact, an electrically switchable wideband metamaterial absorber at low frequencies is presented and investigated in this paper. Our calculated results show that its absorption is over 90% from 400 to 1,000 MHz with the Fermi level of graphene being at 0 eV and the absorption band can be switched by adjusting the Fermi level of graphene without changing its physical structure. Moreover, the surface current distribution enables us to reveal the switchable wideband absorption characteristics of our designed metamaterial absorber. At last, we prove that its absorption property is polarization-insensitive due to the rotational symmetry of the structural unit. This work may provide a further step in the development of switchable sensors and absorbers at low frequencies.

We report a new kind of ultra-thin tunable metamaterial absorber at P band based on the high permittivity and its thermally tunable property of strontium titanate. It is composed of a copper ring and strontium titanate at the top layer, FR4 and copper film at the middle and bottom sections. The absorption of metamaterial absorber reaches 96% at 684 MHz at 300 K and acquires the tunable property of absorption frequency by altering its external temperature. Moreover, we study the surface current and electric field distribution of the metamaterial absorber at 684 MHz at 300 K to explore the physical mechanism of electromagnetic wave absorption. Finally, we prove that the absorption is insensitive to the polarization due to the rotational symmetry of the unit cell, but sensitive to the incident angle and structure size. Our study opens a new prospect in designing the ultra-thin metamaterial absorber at P 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.