Chip-scale terahertz systems

The past decade has seen transformative changes in the terahertz spectrum beyond 100 GHz, both in terms of technological progress and in application development. Of note is the progress made towards enabling efficient and compact Terahertz systems operable at room temperature and deployable at large scales. On the application development, the interest in this spectrum has grown significantly in the band due to the evolution of 5G and steadily increasing large-scale deployments of technology in the sister millimeter-Wave bands. On the technology side, we have seen significant advancements in a multitude of integrated technology substrates in electronics, photonics and in hybrid systems. In the electronics regime, this potpourri of technology has spanned from III-V based devices such as InP HBTs and HEMTs (f_max > 1 THz) to silicon-based IC technology that have shown remarkable advancements in complex systems including chip-scale phased arrays, active and passive imagers, and wireless communication systems. The'THz gap' has steadily been closing in the past ten years due to the technological progress, and attention is being paid now towards closing the'THz' and large-scale'application' gap in the next decade. To enable this shift in paradigm in presence of device limitations, we will need to innovate on new design architectures that allow properties such as reconfigurability, adaptability and multi-functionality in THz chip-scale systems yet being realized in substrates where the devices are inherently not optimally efficient. In this paper, we summarize the advancements in integrated THz systems in the past decade, discuss future challenges and directions to progress towards that goal.