Terahertz radiation has enormous applications in biomedical, industrial quality control, and security areas. Low-cost, mobile devices, such as breath analyzer for disease diagnosis and handheld imaging scanner, will flourish if on-chip terahertz systems are realized. This task is however very challenging. The limitations from the device speed and passive loss have been generally acknowledged. But what has been neglected for long is that the remaining device capability is also not fully released in many widely-used electronic designs (e.g. push-push oscillator). In this talk, a fundamental approach is introduced, which transforms the THz circuit design into a process of electromagnetic-wave synthesis. In this process, electronic devices (e.g. transistor) are utilized as nonlinear, active boundary conditions to control the wave propagation and reflection inside distributed media. Regarding such wave-device interaction, I will present how to reach the device fundamental limits using the optimized wave patterns, and how to efficiently guide and radiate multi-harmonic signals using the orthogonality of different wave modes. Based on these techniques, THz chip prototypes are demonstrated with the highest radiated power and multiplier output frequency in CMOS. The proposed approach can also be extended into other device materials (e.g. GaN) and 2-D domain. Finally, a THz Schottky-diode imaging array is presented with the highest sensitivity in CMOS THz sensors without post processing. This research not only opens up a new way of reaching the limits of electronics, but also lays a foundation for future THz systems for imaging, spectroscopy and inter/intra-chip communications.
Ruonan Han received the B.Sc. in microelectronics from Fudan University in 2007, the M.Sc. in electrical and computer engineering from the University of Florida in 2009, and the Ph.D. from Cornell University in 2014. He is now a research associate in Cornell University. His research is focused on high-performance terahertz integrated circuits and systems using CMOS and GaN technologies. He is the recipient of IEEE Solid-State Circuits Society Pre-Doctoral Achievement Award and IEEE Microwave Theory and Technique Society Fellowship Award. He is also the winner of the Cornell ECE Innovation Award, the Best Student Paper Award (2nd) of the Radio-Frequency Integrated Circuit (RFIC) Symposium, and the Irwin and Joan Jacobs Fellowship.