Nanoantennas design for THz communication

Terahertz (THz) communication is one of the remarkable topics in the field of communication. Terahertz communication, which is one of the promising topics in meeting the rapidly increasing number of devices and the need for data speed and channel capacity, aims to increase the wireless communication frequency band up to terahertz level. When the terahertz frequency is used the wavelength decreases significantly, which causes electromagnetic waves to be more affected by the channel effects. There must be a clear line of sight (LOS) between the transmitter and the receiver in THz communication systems and the electromagnetic wave sent must be highly directive. The use of intelligent reflective surfaces in the terahertz band can provide advantages in the reflected wave being more directive. In this study, different Intelligent Reflective Surface designs in the literature are implemented and a performance comparison is presented in terms of beam characteristics.

The rapid evolution of terahertz (THz) technology has opened new frontiers in high-speed wireless communication, imaging, and sensing. However, the practical deployment of THz systems, particularly in remote or space-constrained environments, is often limited by power constraints and rigid antenna structures. A reconfigurable THz antenna system that is powered by solar energy is suggested. By leveraging real-time energy harvesting, the antenna system maintains operation without external power sources, making it ideal for deployment in remote IoT nodes, CubeSats, or energy-constrained sensor networks. Material used in antenna design is lead glass while gold is used as a radiator, the MIMO antenna loaded with graphene with chemical potential of graphene= 0 works from 2.4–2.5 THz, 3.87–3.98 THz, and 5.17–5.3 THz. The MIMO antenna with graphene chemical potential= 1 eV works from 2.54–2.63 THz, 3.96–4.1 THz, and 5.27–5.45 THz. The MIMO antenna with graphene chemical potential= 2 eV works from 2.6–2.68 THz, 4–4.2 THz, and 5.3–5.55 THz. Gain of antenna at 2.45, 3.95, and 5.3 THz maximum gain obtained at these frequencies is 6, 5 and 7 dBi, respectively. By integrating real-time solar energy harvesting with a tunable THz antenna structure, the design enables self-sustained, high-efficiency operation for remote IoT nodes, CubeSats, and energy-constrained sensor networks, merging green energy and next-generation THz communication in a compact platform. Advantages of the proposed design are self-powered operation, reconfigurable multi-band tuning, high gain, and suitability for diverse THz applications.OPEN ACCESS Received: 23/06/2025 Accepted: 17/09/2025 Published: 23/01/2026

High modulation depth fiber-based modulators working at terahertz (THz) wavelength are of paramount importance for the application of THz communication technology by taking advantages of the low loss, high interference resistance and strong adaptability THz fiber network. Here, we demonstrate a THz modulator based on side-polished THz fiber combined with GaAs film/Au-nanoparticles (Au-Nps). The Au-Nps and the remaining thickness of the side-polishing are careful designed to achieve target resonance wavelengths. The side-polishing region of fiber provides a flat platform for integrating nanostructures to enhanced light-matter interactions which greatly enhances the modulation performance. The experimental results show that this new fiber modulator can achieve the THz wave amplitude modulation under a relatively low irradiation of an external 808 nm laser, with a tunable frequency range of 0.366-1.093 THz and a maximum modulation depth of 99.24%. Besides, resonance frequency can be adjusted by changing the remaining thickness of the device. Moreover, the area of this modulator is only 9 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> which can be easily integrated into THz systems. Therefore, we believe our work will contribute to the developments of high-performance fiber-based THz modulator for applications in THz communication system.

The ever-growing number of interconnected devices and the emergence of high-bandwidth technologies such as holographic communications in mixed reality are driving an exponential growth in the demand for terabits-per-second (Tbps) data rates with sub-milliseconds latency. For this reason, the sixth-generation (6G) wireless communications are moving towards the terahertz (THz) frequency band because of its wider spectral bandwidth availability to enable higher channel capacity and data rates according to the Shannon-Hartley theorem. However, the efficiency of wireless THz signal transmission is reduced by the increased path loss and atmospheric attenuation due to water vapor absorption at THz frequencies, which significantly decreases the signal-to-noise ratio and the spectral efficiency of THz wireless communications. The realization of THz band communications is further impeded by the limited power output of existing compact THz sources due to the extremely low conversion efficiencies. Therefore, it is crucial to develop broadband THz integrated circuits with waveguiding and beamforming functionalities for supporting high data-rate on-chip communications and to provide sufficient gains to counteract the path loss and limited power of THz wireless transmissions. This thesis aims to improve the spectral efficiency of 6G wireless communications via the spatiotemporal shaping of THz waves using silicon photonics. Spatiotemporal light shaping is the basis of nearly all THz photonic devices, ranging from THz wavefront manipulation using metasurfaces to THz planar waveguiding using photonic crystal waveguides. Silicon photonics is a promising material platform for THz wave shaping due to the low-loss propagation of THz waves in high-resistivity silicon and the prospect of a monolithic integrated circuit due to the complementary metal-oxide semiconductor (CMOS) fabrication process compatibility. Silicon metasurfaces allow the wavefront modulation of incident THz radiation by exploiting the generalized Snell’s law of refraction and reflection to beamform highly directional THz waves in a dynamic multi-user communication environment for enhancing the spectral efficiency. Likewise, broadband silicon photonic crystal waveguides allow the in-plane and lossless transport of THz waves to support on-chip high data-rate THz communications that can also seamlessly integrate multiple THz photonic devices in a THz integrated circuit. In addition, silicon electron emitters and silicon gratings potentially allow the on-chip generation of highly intense and broadband THz radiation to counteract the significant THz attenuation. In this thesis, spatiotemporal wave shaping techniques using silicon photonics for enhancing the spectral efficiency of THz band communications is presented. First, a self-adaptive and deep reinforcement learning model for THz beamforming is proposed, which can beamform multiple highly directional THz radiation beam in real-time to serve a dynamically changing multi-user communication environment and improve the signal-to-noise ratio of THz wireless transmission while potentially reducing the communication latency. Second, a broadband THz topological silicon waveguide designed based on valley photonic crystals is proposed for the robust and lossless transport of broadband THz waves for the construction of THz integrated circuits with broadband channel capacity for enabling higher data-rate on-chip communication. Last, the versatility of free-electron radiation from silicon gratings is investigated for the generation of highly intense spatiotemporal wave packets with user-designed group velocities and tunable intensity profile, with the potential to realize integrated high-power THz sources. The deep learning beamforming model, the broadband topological waveguide designs, and the free-electron radiation intensity shaping techniques presented in this thesis extends beyond the THz regime and are scalable across the entire electromagnetic spectrum. The CMOS process compatibility of silicon metasurfaces, silicon planar waveguides, along with silicon electron emitters and silicon gratings offers the opportunity to realize a broadband THz photonic integrated circuit with waveguiding, wave generation and beamforming functionalities for enhancing the spectral efficiency of THz communications in 6G wireless networks.

Graphene-based terahertz (THz) metasurfaces combined with metallic antennas have the advantages of ultra-small thickness, electrical tunability, and fast tuning speed. However, their tuning ability is limited by non-independently tunable pixels and low modulation depth due to the ultra-small thickness of graphene. Here, we demonstrate a reconfigurable THz phase modulator with 5×5 independently tunable units enabled by switching the voltages applied on 10 graphene ribbons prepared by laser cutting. In addition, by introducing quasi-bound states in the continuum resonance through a designed double C-shaped antenna, the efficiency of the device is enhanced by 2.7–3.6 times under different graphene chemical potentials. Experimental results demonstrate that a focus can be formed, and the focal length is changed from 14.3 mm to 22.6 mm. This work provides potential for compact THz spatial light modulators that may be applied in THz communication, detection, and imaging.

The concept and analysis of a graphene plasmonic nanoantenna over a SiO 2 /Si substrate at terahertz (THz) band are presented. The performance enhancement of the antenna is proposed by dynamically controlling the surface conductivity of graphene using an electric field effect. The controlling ability of graphene via gate voltage enables frequency reconfiguration of the antenna over a wide range of 2.56–4.98 THz. The performance merits of the antenna are its high directivity, broadside radiation pattern, low reflection coefficient, stable impedance and high miniaturisation. The proposed graphene plasmonic antenna has potential to be used for THz communication.

Considering that the metastructures (MSs) previously proposed usually perform in a single state, herein, a multifunctional and tunable ultra-broadband linear to circle (LTC) polarization converter based on phase transition material vanadium dioxide ( V O 2 ) is proposed in the terahertz (THz) region. By manipulating the temperature, the function of the LTC polarization conversion (PC) can be conveniently switched between transmission and reflection states. When the environment temperature is low, V O 2 presents the insulating state, and the MS can achieve ultra-wideband LTC PC from 0.57–0.83 THz with a relative bandwidth (RB) of 37.3%. When the temperature exceeds 68°C, LTC PC with the frequency bandwidth of 0.83–1.20 THz and 0.83–1.17 THz can be obtained in a reflection state when electromagnetic waves propagate forward and backward, whose RBs are 36.4% and 34.0%, respectively. Meanwhile, a broadband linear to linear (LTL) PC can also be realized in the range of 1.19–1.41 THz for the forward incident wave and 1.16–1.37 THz for the backward incident wave. The designed MS offers an effective method to realize four different functions and has tremendous potential value in realizing THz modulation devices, electromagnetic cloaking, and communication systems.

A well-known empirical rule for the demand of wireless communication systems is that of Edholm's law of bandwidth. It states that the demand for bandwidth in wireless short-range communications doubles every 18 months. With the growing demand for bandwidth and the decreasing cell size of wireless systems, terahertz (THz) communication systems are expected to become increasingly important in modern day applications. With this expectation comes the need for protecting users' privacy and security in the best way possible. With that in mind, we show that quantum key distribution can operate in the THz regime and we derive the relevant secret key rates against realistic collective attacks. In the extended THz range (from 0.1 to 50 THz), we find that below 1 THz, the main detrimental factor is thermal noise, while at higher frequencies it is atmospheric absorption. Our results show that high-rate THz quantum cryptography is possible over distances varying from a few meters using direct reconciliation, to about 220m via reverse reconciliation. We also give a specific example of the physical hardware and architecture that could be used to realize our THz quantum key distribution scheme.

Suitable power levels remain constant challenges in terahertz (THz) communications. This work analytically investigates a 1.94 THz resonant tunneling diode-gated high-electron mobility transistor (RTD-gHEMT)-based oscillator along with a graphene antenna for future 6G wireless networks. We obtain the negative conductance of a distributed circuit model from experimental results of an InGaAs/AlAs RTD oscillator. Analytical results show the device notably achieves an output power up to 14 mW (&#x223C;11.5 dBm) whilst operating at frequencies as high as 1.94 THz. Furthermore, the RTD-gHEMT device has a 37.4 nm gate length, which renders a substantial decrease in the system form factor. These unique features place the device as part of potential solutions for generation and transmission of THz signals in 6G networks.

The paper presents the prototyping of a high-order modulation (64-QAM) terahertz (THz) communication system over 100 Gbps. To begin with, the channel capacity and spectrum efficiency of a THz link are analyzed based on Shannon’s theorem and the state of the art technology. Then, a Monolithic Microwave Integrated Circuit (MMIC) frequency multiplier and a secondary harmonics mixer are designed and manufactured. Finally, we prototype the THz communication system and realize the transmission data rate over 100 Gbps with 64-QAM in lab. The test results in our study paves the way towards the fulfillment of the broadband and large capacity required by future sixth-generation (6G) mobile communication systems.

In this paper, we study a multiuser indoor Terahertz (THz) communication system with antenna array. To capture the distance-frequency dependent peculiarities of THz channels, we design a distance-aware multi-carrier transmission scheme with hybrid beamforming and antenna subarray selection. Specifically, a low complexity greedy subarray selection algorithm is proposed. Simulation results are provided to verify the effectiveness of the transmission policy as well as the antenna subarray selection algorithm for the multiuser THz system.

This paper presents a comprehensive review of integrated terahertz (THz) and free-space optical (FSO) communication systems, focusing on their potential to address the escalating demands for high-capacity, long-distance, and ultra-reliable transmission in future six-generation (6G) and space–air–ground integrated networks (SAGIN). The study systematically examines recent advancements in three critical areas: channel modeling, transmission performance, and integrated system architectures. Specifically, it analyzes THz and FSO channel characteristics, including attenuation mechanisms, turbulence effects, pointing errors, and noise sources, and compares their complementary strengths under diverse atmospheric conditions. Key findings reveal that THz communication achieves transmission rates up to several Tbps over distances of several kilometers but is constrained by molecular absorption and weather-induced attenuation, while FSO offers superior bandwidth-distance products yet suffers from turbulence-induced fading, posing significant reliability challenges. The integration of THz and FSO through adaptive switching strategies (e.g., hard and soft switching) demonstrates enhanced reliability and spectral efficiency, with experimental results showing seamless data rates exceeding Tbps in hybrid systems. However, challenges persist in transceiver hardware integration, algorithmic optimization, and dynamic resource allocation. The review concludes by identifying future research directions, including the development of unified channel models, shared architectures, and intelligent switching algorithms to achieve robust integrated communication infrastructures.

The importance of terahertz (THz) detection lies in its ability to provide detailed information in a non-destructive manner, making it a valuable tool across various domains including spectroscopy, communication, and security. The ongoing development of THz detectors aims to enhance their sensitivity, resolution and integration into compact and portable devices such as handheld scanners or integrated communication chips. Generally, two-dimensional (2D) materials are considered potential candidates for device miniaturization but detecting THz radiation using 2D semiconductors is generally difficult due to the ultra-small photon energy. However, this challenge is being addressed by the advent of topological semimetals (TSM) with zero-bandgap characteristics. These semimetals offer low-energy excitations in proximity to the Dirac point, which is particularly important for applications requiring a broad detection range. Their distinctive band structures with linear energy-momentum dispersion near the Fermi level also lead to high electron mobility and low effective mass. The presence of topologically protected dissipationless conducting channels and self-powered response provides a basis for low-energy integration. In order to establish paradigms for semimetal-based THz detectors, this review initially offers an analytical summary of THz detection principles. Then, the review demonstrates the distinct design of devices, the excellent performance derived from the topological surface state and unique band structures in TSM. Finally, we outline the prospective avenues for on-chip integration of TSM-based THz detectors. We believe this review can promote further research on the new generation of THz detectors and facilitate advancements in THz imaging, spectroscopy, and communication systems.

The promising way to provide sufficient transmission capacity is by accessing transmission bands at higher carrier frequencies. This desire for higher carrier frequency or more bandwidth led researchers to take advantage of the terahertz (THz) spectrum. The opportunity for large bandwidth in the THz band leads to the possibility of easy high data rate transmission. In spite of the advantages, the THz band suffers from large free space path loss. In the development of THz communication systems, the antenna is the most significant component. Especially, the focus is to design highly directive antennas, because it enhances the performance of the overall system by compensating the large path loss at THz and thus improves the signal-to-noise ratio. This chapter presents different types of THz antennas that include planar, reflectarray, horn antenna and lens antenna. The emphasis is on presenting the latest trend of designing THz antennas using carbon-based materials, such as graphene and carbon nanotubes. The performance of these antennas has been compared with that of traditional copper based THz antennas, by critically analyzing their properties. For completeness, a brief discussion on THz power sources has been made in this chapter. A comprehensive discussion on different fabrication techniques has been provided to appraise the reader of the general fabrication processes of THz components.

Focused THz wave from a spintronic terahertz Fresnel Zone Plate emitter