Terahertz electromagnetic waves, situated in between radio waves and light waves, are expected to be applicable in various industrial applications. In particular, research and development are accelerating in recent years as a frequency resource indispensable for realizing ultrahigh-speed wireless communication systems.

This workshop was aimed to present and discuss cutting-edge millimeter- and terahertz-wave devices/circuits technologies and their applications to ultrahigh-speed wireless communication systems by researchers who are active at the forefront of a wide range of materials, devices, circuits, and systems research and development, attracting 18 participants. We deeply discussed on wide aspects of the technological subjects, bottlenecks, solutions and practical timelines in relation to the presentations given by four renowned leading researchers and questions, and deepened common understanding of future prospects.

Dr. Safumi Suzuki (Tokyo Inst. of Tech.) presented the experimental works for 300-GHz band 20-Gbit/s class sub-terahertz wave radio transmission experiment using resonant tunnel diodes as sub-terahertz oscillator/detector devices and addressed the prospect for 100-Gbit/s class wireless communications.

Dr. Minoru Fujishima (Hiroshima Univ.) reported on advanced technology and future prospect of a front-end transceiver circuit for 300-GHz band radio communication by using complete silicon CMOS IC technology.

Dr. Masataka Higashiwaki (NICT) presented advances in Ga2O3 power devices including the presenter's pioneering crystal growth technology of Ga₂O₃ as a next-generation high-power high-speed transistor material and the current status and future prospect of application of Ga₂O₃ to the transistor devices.

Dr. Taiichi Otsuji (Tohoku Univ.) reported the discovery and development status of a new terahertz laser/amplifier devices using graphene, a carbon-atomic monolayer material, as a gain medium. In response to these state-of-the-art research and development works leading the world, the attendees stimulated discussions deeply on issues to be coped with, benchmarking with existing/alternative technologies, as well as future prospect.

Now ITU-T is working in active to extend the frequency allocation beyond the present upper limit at 275 GHz up to 3000 GHz, being scheduled for the next fiscal year. In this situation, This workshop had a great merit for contributing to the materialization of the technology roadmap on the future ultrahigh-speed wireless communications towards beyond 6G on the way via post 5G followed by the next generation 6G. This workshop gave us very useful opportunity to understand the state-of-the-art research and development situation and to share common recognitions about technical issues and future outlooks against the independent future image of each participant envisioned.