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%.

Metal hybrid waveguide couplers, which are crucial passive structures in terahertz (THz) in-phase-quadrature (IQ) mixers, have raised significant attention in the development of high-speed communication systems. Spoof surface plasmon polariton (SSPP) mode, a surface wave transmission mode, possesses excellent characteristics such as localized field enhancement and energy concentration. To further expand the operating bandwidth of THz coupler and improve the balance performance between IQ paths, this article combines the SSPPs’ structure with the waveguide coupler, converts the low-pass characteristics of the traditional SSPPs’ transmission lines and high-pass rectangular waveguide transmission lines into bandpass ones, and proposes an SSPPs’ interdigital coupled quasi-periodic coupler, treating the hybrid waveguide coupler as a quasi-periodic structure, utilizing the transmission mode and dispersion relation of SSPPs to concentrate and enhance the local field strength, thus improving the coupling performance. The proposed structure achieved better amplitude balance performance and expanded the operating bandwidth. An SSPP-coupled hybrid waveguide coupler was designed and fabricated. The simulated amplitude imbalance is less than 0.3 dB and the measured one remains below 0.75 dB across the frequency range of 150–260 GHz, which has a significantly larger bandwidth than the WR-4 standard rectangular waveguide with the working frequency range of 170–260 GHz. The measured phase imbalance is within 2.2 $^{\circ}$ , and the total insertion loss is within 1.3 dB. This novel SSPPs’ coupler proves the feasibility of a promising structural design using bandpass transmission lines in replacement of traditional high-pass transmission lines in metal hybrid waveguide couplers for large-bandwidth and high-performance THz IQ mixing devices.

High-speed direct modulation devices are of great significance for the development of high-speed communication systems with large bandwidth, miniaturization, and low complexity. However, an increase in the carrier frequency in the sub-terahertz band and above will negatively impact high-performance direct modulation devices due to the large insertion loss and low on–off ratio. Based on the traveling-wave modulation mechanism, this article adopts the zero-phase-difference amplitude modulator design method. More specifically, a 1- $\mu$ m small anode Schottky diode is combined with a Z-type matching structure to form a dual-resonant coupling dynamic tunable unit. Interunit coupling is found to further improve the on–off ratio. In this way, high-speed dynamic modulation is performed for the transmission traveling-wave amplitude with low insertion loss and a high on–off ratio. On this basis, a 0.14-THz on–off keying (OOK) high-speed traveling-wave modulator is proposed, and our results showed that a on–off ratio of 25.4 dB could be achieved at the zero-phase-difference point by only using two dynamic structural units. Meanwhile, the control voltage could be adjusted to achieve high-speed modulation with a phase difference of only 3.66 $^\circ$ during the entire control voltage transition, a data rate of 24 Gb/s, and 33.99% sidebands occupation.

Compared with GaAs Schottky barrier diodes (SBDs), GaN SBDs offer a remarkable increase in the power capacity. However, GaN-based doublers face limitations in their continuous-wave output power due to challenges in the thermal dissipation. To address this issue, this article proposes a novel thermal resistance calculation model tailored to guide the development of devices with minimized thermal resistance and to streamline the procedure for extracting the anode temperature. This model is also suitable for a broad range of compound semiconductor processes. Based on this, the device’s thermal resistance structure was optimized, facilitated by the adoption of the GaN/SiC monolithic integration process. Subsequently, prototypes centered at 140, 170, and 220 GHz were tested. All sources represent a breakthrough in maximum output power without power synthesis technology, marking a state-of-the-art accomplishment. The measured room-temperature output power levels are as follows: 352 mW for the 140-GHz doubler, 350 mW for the 170-GHz doubler, and 109 mW for the 220-GHz doubler (higher power amplifiers are missing).

In this paper, we present a new type of isolator based on one-way surface magnetoplasmons (SMPs) at microwave frequencies, and it is the first time that an experimental prototype of isolator with wideband and ultra-high isolation is realized using SMP waveguide. The proposed model with gyromagnetic and dielectric layers is systematically analyzed to obtain the dispersion properties of all the possible modes, and a one-way SMP mode is found to have the unidirectional transmission property. In simulation and experiment with metallic waveguide loaded with yttrium–iron–garnet (YIG) ferrite, the scattering parameters and the field distributions agree well with the analysis and verify the one-way transmission property. The isolation is found to be as high as 80 dB and the typical value of insertion loss is 1 dB. Besides, the one-way transmission band can be controlled by changing the magnetic bias. From theoretical analysis and simulation, it is found that with a tiny value of 10 Oe of the magnetic bias, the relative bandwidth can be tuned to be greater than 50%. Compared with conventional isolators, this one-way SMP isolator has the advantages of ultra-high isolation, wide relative frequency band, and requires much smaller bias field, which has promising potential in non-reciprocal applications.