Advanced Terahertz Devices And Systems Toward 6G And Beyond

A wide untapped region exists between radio waves and light in the electromagnetic spectrum: terahertz (THz) waves. THz frequencies combine the penetration of radio waves and the large bandwidth of light, which makes them excellent candidates for next-generation information communication technology, 6G and beyond, such as ultra-broadband wireless communication, spectroscopic sensing, nondestructive imaging, and high-resolution ranging. However, THz frequencies are at the upper limit of the capabilities of conventional electronics, and the development of THz devices and systems is a challenging field of interdisciplinary research. In particular, it is difficult to generate a significant amount of power from THz sources. THz devices must, therefore, be as efficient as possible to conserve limited power. Resonant tunneling diodes are a major candidate for both THz transmitters and receivers because of their simple and low-power electronic devices. In addition, a low-loss platform for integrating THz devices is essential for various practical systems. However, the propagation loss of transmission lines based on conventional electronics is high in the THz region, mainly owing to the high ohmic loss in metals. Thus, an alternative, metal-free integrated platform based on THz silicon photonics or photonic crystals is necessary to manipulate THz waves.