Recent progress in two-dimensional materials for terahertz protection

A Polarization-Insensitive, Vanadium Dioxide-Based Dynamically Tunable Multiband Terahertz Metamaterial Absorber

A tunable multiband terahertz metamaterial absorber, based on vanadium dioxide (VO2), is demonstrated. The absorber comprises a three-layer metal-insulator-metal (MIM) configuration with a split ring and slots of VO2 on the uppermost layer, a middle dielectric substrate based on silicon dioxide (SiO2), and a gold reflector on the back. The simulation results indicate that, when VO2 is in the metallic state, the proposed metamaterial exhibits nearly perfect absorption at six distinct frequencies. The design achieves an average absorption of 98.2%. The absorptivity of the metamaterial can be dynamically tuned from 4% to 100% by varying the temperature-controlled conductivity of VO2. The proposed metamaterial absorber exhibits the advantages of polarization insensitivity and maintains its absorption over 80% under different incident angle conditions. The underlying physical mechanism of absorption is explained through impedance matching theory, interference theory, and the distribution of electric fields. The ability to achieve multiband absorption with tunable characteristics makes the proposed absorber a promising candidate for applications in terahertz sensing, imaging, communication, and detection. The polarization insensitivity further enhances its practicality in various scenarios, allowing for versatile and reliable performance in terahertz systems.

High-Performance Transparent Ultrabroadband Electromagnetic Radiation Shielding from Microwave toward Terahertz

In the era of fifth-generation networks and Internet-of-Things, the use of multiband electromagnetic radiation shielding is highly desirable for next-generation electronic devices. Herein, we report a systematic exploration of optoelectronic behaviors of ultrathin-silver-based shielding prototype (USP) film structures at the nanometer scale, unlocking the transparent ultrabroadband electromagnetic interference (EMI) shielding from microwave to terahertz frequencies. A theoretical model is proposed to optimize USP structures to achieve increased transparency, whereby optical antireflection resonances are introduced in dielectrics in conjunction with remarkable EMI shielding capability. USP can realize a state-of-the-art effective electromagnetic radiation shielding bandwidth with measured frequencies from 8 GHz up to 2 THz. Experimental results show that a basic USP (dAg = 10 nm) offers an average shielding efficiency of ∼27.5 dB from the X- to Ka-bands (8-40 GHz) and maintains a stable shielding performance of ∼22.6 dB across a broad range of 0.5-2 THz, with a measured optical transmittance of ∼95.2%. This extraordinary performance of ultrathin-silver-based film structures provides a new ultrabroadband EMI shielding paradigm for potential applications in next-generation electronics.

Printable and low-cost perfect terahertz absorber realized by a laser-induced graphene metasurface

Terahertz (THz) absorbers are highly desired with the rapid development of THz technology. Although metasurface-based absorbers can realize perfect absorption, their fabrication often requires complicated micro-nano-processing with a high cost. In this paper, fast printable and low-cost metasurface absorbers based on a laser-induced graphene (LIG) technique are proposed. Experimental results demonstrate that these two metasurfaces can achieve maximum absorptions of 99.3% and 99.9% at their resonant frequencies in an incident angle range of ±55°. Fabrication of a metasurface with a size of 1 × 1 cm costs only 11 s. The absorbers may be applied in THz dichroism and communications.