Electrically tunable terahertz metadevices: Materials, functions, and applications

Terahertz (THz) radiation exhibits high penetration, low energy, and unique fingerprint features, resulting in wide applications in sensing, nondestructive detection, imaging, and communications. The output responses of the majority of conventional THz devices are determined by fixed structural parameters defined during fabrication. Dynamic THz metadevices with reconfigurable functionalities can be realized by applying thermal, electrical, or optical stimuli. Electrically tunable THz metadevices achieve dynamic control of the amplitude, phase, frequency, and polarization of THz waves through the incorporation of functional materials and architectures, including semiconductors, phase-change materials, two-dimensional materials, liquid crystals, and microelectromechanical systems. In contrast to thermal or optical excitation, electrically driven devices provide fast responses, low energy consumption, and high compatibility with current electronic control circuitry. This review provides an in-depth examination of the mechanisms and materials facilitating tunability in electrically tunable THz metadevices, along with their modulation of THz parameters and representative applications in spatial light modulators, photonic memory, beamforming, metalenses, vortex beam modulation, holographic encryption, and high-speed 6G modulators. Finally, prospects for the future evolution and technological trends of electrically tunable THz metadevices are presented.