Topological and Reconfigurable Terahertz Metadevices

Abstract

The terahertz (THz) frequency range, situated between microwave and infrared radiation, has emerged as a pivotal domain with broad applications in high-speed communication, imaging, sensing, and biosensing. The development of topological THz metadevices represents a notable advancement for photonic technologies, leveraging the distinctive electronic properties and quantum-inspired phenomena inherent to topological materials. These devices enable robust waveguiding capabilities, positioning them as critical components for on-chip data transfer and photonic integrated circuits, particularly within emerging 6G communication frameworks. A principal advantage resides in the capacity to maintain low-loss wave propagation while effectively suppressing backscattering phenomena, a critical requirement for functional components operating at higher frequencies. In parallel, by leveraging advanced materials such as liquid crystals, plasma, and phase-change materials, these devices facilitate real-time control over essential wave parameters, including amplitude, frequency, and phase, which augments the functionality of both communication and sensing systems, opening new avenues for THz-based technologies. This review outlines fundamental principles of topological components and reconfigurable metadevices operating at THz frequencies. We further explore emerging strategies that integrate topological properties and reconfigurability, with a specific focus on their implementation in chip-scale photonic circuits and free-space wavefront control.

Fig. 1.

On-chip topological THz metadevices (A) Photonic supercoupling in silicon topological waveguides [26]. (B) On-chip THz taper-free waveguides [27]. (C) THz topological photonics for on-chip communication [30]. (D) Landmark self-similar multi-resonant units with gradually changed resonant peaks [33]. (E) Quasi-BIC-based metasensors [34]. (F) On-chip topological THz biosensors [31]. (G) Nonlinear generation and topologically tuned confinement of THz waves [36]. (H) On-chip active supercoupled topological cavity [37].

Fig. 2.

THz topological metadevices for free space applications. (A) 3D topological insulator Bi₂Te₃ [40]. (B) Anomalous wave propagation in topological transition metadevice [47]. (C) Milliwatt THz harmonic generation [48]. (D) Spin-decoupled wavefront manipulation [49]. (E) Subcycle observation of lightwave-driven Dirac currents [51]. (F) Design of a topological laser [52].

Fig. 3.

LC-based reconfigurable THz metadevices. (A) Phase gradient metasurface with liquid crystal-enhanced cavity mode conversion [62]. (B) Transmissive digital coding metasurfaces based on liquid crystals [66]. (C) LC integrated programmable metasurfaces [67]. (D) Vortex vector beam conversion [69]. (E) Individually addressable transmissive metadevice [68]. (F) Flexible manipulation enabled by anisotropic liquid crystal coupled chiral metasurfaces [71]. (G) Dielectric-liquid crystal-plasmonic metadevice [75].

Fig. 4.

Plasma and PCMs-based THz reconfigurable metadevices. (A) Reconfigurable beamforming silicon plasma antenna [77]. (B) Gate-voltage tunability of plasmons [82]. (C) Reconfigurable electromagnetically induced transparency metamaterial [92]. (D) Reversible switching of the metasurface-induced transparency in the THz spectrum [100]. (E) Electrically addressable integrated intelligent THz metasurface [101].

Fig. 5.

THz reconfigurable topological metadevices. (A) Reconfigurable chiral spintronic THz emitters [113]. (B) Non-volatile reconfigurable phase change topological photonics [116]. (C) Electrically tunable topological notch filter [117]. (D) Ultrahigh-Q THz topological cavities on a chip [120]. (E) Phototunable chip-scale topological photonics [121]. (F) On-chip topological beamformer [122].