掲載種別：研究論文（学術雑誌）   出版者・発行元：IEEE Transactions on Terahertz Science and Technology  

Photonics-based terahertz (THz) technology has emerged as a key enabler for future 6G networks, offering ultrawide bandwidth and cross-domain applications such as high-capacity communications and high-resolution radar. However, conventional THz photomixing architectures rely on optical frequency combs or dual lasers, which impose severe limitations in terms of size, weight, power, and cost (SWAP-C). In this paper, we propose a cost-effective photonic THz signal generation scheme based on only a single electro-optically wavelength tunable laser (WTL). Moreover, two representative applications are investigated. For THz wireless communications, the proposed system employs a fiber-delayed self-multiplexer to realize on-off keying modulation via wavelength switching, together with a T-flip-flop-based decoding method that enhances data rate scalability and transmission security. An error-free 100 Mbit/s transmission at 280 GHz validates the feasibility of this low-SWAP-C communication system. For radar applications, the same single-WTL platform enables linearly frequency-modulated (LFM) THz signal generation with waveform reconfigurability. Both sawtooth and triangle LFM THz signals are achieved, providing enhanced bandwidths of 11.5 GHz and 5 GHz with chirp rates exceeding 0.027 GHz/ns at the 300-GHz-band. These results highlight the versatility of single-WTL-based photomixing, presenting a low-SWAP-C solution for future photonic THz communication and radar systems.

DOI： 10.1109/tthz.2026.3684329

Scopus

掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：2025 International Symposium on Antennas and Propagation Isap 2025  

This work presents a photonic-integrated InGaAs/SiC UTC-PD-fed microstrip stub array antenna for efficient 300 GHz fan-beam generation. The InGaAs UTC-PD is transferred onto a high-thermal-conductivity SiC substrate using the flip-wafer bonding technique. Experimental results demonstrate a peak power gain at 300 GHz, with a 3 dB bandwidth of 12 GHz. The measured H-plane radiation pattern exhibits a 3 dB beamwidth of 35° and a sidelobe level of -13 dB. The monolithic integration of photonic circuits and antennas enables compact fan-beam THz sources for wireless communication, imaging, and sensing.

DOI： 10.23919/isap63122.2025.11362206

Scopus

掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：2025 IEEE International Topical Meeting on Microwave Photonics Mwp 2025  

Rapid and stable terahertz (THz) frequency tuning is crucial for emerging applications like 6G communications and integrated sensing and communication (ISAC). This paper demonstrates a novel optoelectronic scheme, employing fixed-wavelength lasers, tunable optical single-sideband modulation (SSBM), and optoelectronic photomixing in a uni-traveling carrier photodiode (UTC-PD) to achieve such agility. The system leverages the capability of SSBM for precise and rapid sideband control, achieving 6.3 GHz frequency sweeps around 300 GHz within 15 ns and supporting diverse modulation waveforms (step, triangular, sine). This approach offers a concise, efficient, and potentially cost-effective solution for advanced THz systems, significantly contributing to the development of flexible and high-performance THz sources.

DOI： 10.1109/mwp65272.2025.11372036

Scopus

担当区分：筆頭著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Optical Switching and Networking  

Future 6G communication systems are envisioned to expand their carrier frequency to the THz region, where a broad unexplored region of spectrum is available. With this expansion, THz wireless communication has the potential to achieve ultra-high data transmission rates of up to 100 Gbit/s. However, as large amounts of data are transmitted in an open wireless environment, there are significant concerns regarding communication security due to the susceptibility to eavesdropping, interception, and jamming. In this work, we proposed a secure approach for THz wireless communication based on spatial wave mixing and flexible beam steering. To achieve this, two frequency-modulated THz waves, which are generated by photonic THz sources and carry encrypted information with true randomness, are mixed at a THz envelope detector with an exclusive-OR logic operation. We analyzed the possible spatial location for the THz detector to ensure a secure microcell network deployment. Our results demonstrate that the size of the decryptable region is directly dependent on the directivity and width of the emitted THz beam. To address this, we have developed an array antenna with integrated uni-traveling-carrier photodiodes (UTC-PDs), which is capable of generating THz waves while also improving the flexibility of beam pointing, allowing for greater control over the location and size of the decodable region. By controlling fiber-optic delay lines, we successfully demonstrated that the directional gain of a 200 GHz wave is increased by 8 dB through a 1 × 3 UTC-PD-integrated planar bowtie antenna (PBA) array, together with continuous beam steering from -20° to 10°. Additionally, using a 1 × 4 UTC-PD-integrated PBA array to emulate two encryption transmitters and a Femi-level managed barrier diode to detect spatially mixed THz waves, we successfully achieved a feasibility experiment for real-time 200 Mbit/s location-based decryption in the 200 GHz band. These results indicate that the proposed scheme is feasible for secured THz communication, and would be a powerful candidate to mitigate security risks in 6G microcell networks.

DOI： 10.1016/j.osn.2024.100773

Web of Science

Scopus

担当区分：筆頭著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Infrared Millimeter and Terahertz Waves  

THz technology has the potential to revolutionize various fields, including high-speed wireless communication, medical imaging, and spectroscopy. One challenge facing THz technology, however, is the limited output power (on the order of microwatts) of photonic THz sources (e.g., uni-traveling-carrier photodiode). Researchers are therefore exploring THz beam steering techniques to maximize their power effectiveness. To this end, we propose a photonic THz beam steering method that utilizes fiber chromatic dispersion, eliminating the need for energy-consuming active electronics. This paper explains its basic operating principle, fabrication and performance analysis of the associated THz array antenna, and demonstrates the feasibility of achieving a 300 GHz beam steering within 10^∘ by means of dispersion-varied polarization-maintaining fibers. In conclusion, the present scheme can greatly enhance the power efficiency of photonic THz sources, and enable the potential advantages of seamless integration with fiber-optic networks, including reduced complexity, simplified operation, low power consumption, and cost-effectiveness.

DOI： 10.1007/s10762-024-00975-0

Web of Science

Scopus

その他リンク： https://link.springer.com/article/10.1007/s10762-024-00975-0/fulltext.html

開催年月日： 2024年11月

開催年月日： 2023年9月

会議種別：口頭発表（招待・特別）  

開催地：Kumamoto, Japan  

Invited

開催年月日： 2023年3月

We developed a THz-wave power-combination and beam-steering system driven by an optoelectronic phased array. The 300-GHz waves from an antenna-coupled InP/InGaAs UTC-PD array are combined with 16-dB gain and steered continuously over a 30° range.

会議種別：シンポジウム・ワークショップ パネル（公募）  

開催年月日： 2025年12月