Huygens metasurfaces have demonstrated remarkable potential in perfect transmission and precise wavefront modulation through the synergistic integration of electric resonance and magnetic resonance. However, prevailing active or reconfigurable Huygens metasurfaces, based on all-optical systems, encounter formidable challenges associated with the intricate control of bulk dielectric using laser equipment and the presence of residual thermal effects, leading to limitations in continuous modulation speeds. Here, we present an ultrafast electrically driven terahertz Huygens metasurface that comprises an artificial microstructure layer featuring a two-dimensional electron gas (2DEG) provided by an AlGaN/GaN heterojunction, as well as a passive microstructure layer. Through precise manipulation of the carrier concentration within the 2DEG layer, we effectively govern the current distribution on the metasurfaces, inducing variations in electromagnetic resonance modes to modulate terahertz waves. This modulation mechanism achieves high efficiency and contrast for terahertz wave manipulation. Experimental investigations demonstrate continuous modulation capabilities of up to 6 GHz, a modulation efficiency of 90%, a transmission of 91%, and a remarkable relative operating bandwidth of 55.5%. These significant advancements substantially enhance the performance of terahertz metasurface modulators. Importantly, our work not only enables efficient amplitude modulation but also introduces an approach for the development of high-speed and efficient intelligent transmissive metasurfaces.

As a key potential component of future sixth-generation (6G) communication systems, terahertz (THz) technology has received much attention in recent years. However, a lack of effective high-speed direct modulation of THz waves has limited the development of THz communication technology. Currently, most high-speed modulators are based on photonic systems that can modulate electromagnetic waves with high speed using sophisticated optoelectronic conversion techniques. Yet, they usually suffer from low conversion efficiency of light to the THz range, resulting in low output power of the modulated THz waves. Here, we describe a guided-wave modulator for THz signals whose performance nearly matches that of existing in-line fiber-optic modulators. Our results demonstrate a maximum modulation depth greater than 20 dB (99%) and a maximum sinusoidal modulation speed of more than 30 GHz, with an insertion loss around 7 dB. We demonstrate the capabilities of this modulator in a point-to-point communication link with a 25 Gbit/s modulation speed. Our modulator design, based on near-field coupling of a THz transmission line to a single resonant meta-element, represents a powerful improvement for on-chip integrated high-performance THz devices.

High-speed logic modulation of terahertz (THz) waves is crucial for future communications, yet a technology gap persists. Here, we report a dual gate–controlled two-dimensional electronic gas logic modulation metasurface that enables symmetric and asymmetric electron distribution states through independent control of the two electron transport channels. The transition between these two states leads to various response modes in the metasurface and notably increases the diversity of the spectrum transformation, resulting in a multivalued relationship in which each output corresponds to more than one input signal, thus establishing the logical modulation. Our results demonstrate the common logical functions of AND, OR, XOR, XNOR, NOR, and NAND at different frequencies with a modulation speed faster than 250 picoseconds. This work offers a unique avenue for the high-speed, free-space logical operation of THz waves and increases the security of secure communication.

In the practice of terahertz upstream and downstream systems, the inconsistency of up/downstream channels and terahertz frontends, unpredictable nonideality of terahertz transceivers, and crosstalk between channels lead to short communication range and limits application scenarios of terahertz communication systems. In this paper, an all-solid-state terahertz full-duplex upstream and downstream communication system working in the 220 GHz band is proposed with a 630 m communicationdistance.Frequencydivisionmultiplexingandorthogonal frequency division multiplexing(OFDM) are employed. Terahertz frontend and real-time demodulation baseband circuit are designed, and a debugging algorithm for power distribution in bidirectional communication systems is proposed, which is capable of finding the feasible solution of the furthest distance of bidirectional communication system in the premise of unclear performance of RF frontend and baseband systems. The system performance and debugging algorithm are verified in the experiment. The field test shows a communication distance of 630m under the communication speed of 20.8 Gbit/s per channel, with a bit error rate is less than 10 ⁻¹⁰ , which supports real time bidirectional non-compression-4K video transmission at the same time. The estimated maximum communication distance of the system can exceed 1 km, and the difference in the estimated maximum communication distance between upstream and downstream is less than 7%.

Terahertz (THz) wireless links have attracted significant attention due to their pivotal role in next-generation communication systems. Multiplexing is one of the key techniques used to expand channel capacity for high-speed data transmission in point-to-point wireless communication. Using a pair of multifunction metasurfaces, we construct mode division multiplexing (MDM) in THz wireless link with cylindrical vector beams (CVBs) as orthogonal channels. The proposed metasurfaces integrate the functions of CVB generation and vector mode multiplexing, greatly simplifying MDM links. The simulated and measured results show that the multiplexer/demultiplexers are broadband in the frequency range of concern (from 0.36 to 0.44 THz) and compatible with frequency-division-multiplexing and polarization-division-multiplexing. Importantly, we experimentally accomplished a two-channel MDM in a direct modulation THz communication system at 0.36 THz in which the maximum modulation speed is 5 GHz (isolation>20dB). This study will lay the groundwork for CVB-based multidimensional multiplexing in the THz spectrum, potentially enhancing high-capacity THz communication.

As an exceptional nonlinear material, graphene offers versatile appealing properties, such as electro‐optic tunability and high electromagnetic field confinement in the terahertz regime, spurring advance in ultrashort pulse formation, photodetectors and plasmonic emission. However, limited by atomic thickness, weak light–matter interaction still limits the development of integrated optical devices based on graphene. Here, an exquisitely designed meta‐cavities combined with patterned graphene is used to overcome this challenge and promote THz‐graphene interaction via terahertz location oscillation. By using an 800 nm pump laser, the local field‐induced strong interaction allows sensitive responses to the ultrafast energy transfer from the ultrafast optical pump to graphene electron heat, enabling 46.2% enhancement of terahertz transparency. Such optical modulation of terahertz waves shows ultrafast response in delay less than 10 ps. Moreover, thanks to the nature of graphene, the device shows unique potential for electrically dynamic tuning and further bandwidth broadening.