A Compact System for Terahertz Imaging and Spectroscopy

Terahertz Metalens Antenna
  • Project Details:
Project Code:T42-103/16-N
Project Title:A Compact System for Terahertz Imaging and Spectroscopy
Project Coordinator:Professor Chi-hou CHAN
Coordinating Institution:City University of Hong Kong
Participating Institution(s):The University of Hong Kong
  • Abstract
Terahertz (THz) wave is in the electromagnetic spectrum between the conventional microwave and infrared regions with a wide range of applications. Penetration of THz wave is susceptible to water molecules and can distinguish intrinsic contrast between normal and cancerous tissues. When used in imaging, foreign objects in drugs and foods can be conveniently detected.

Researchers hoping to exploit this promising frequency regime must confront the enormous entry barriers attributed to the cost of the testing equipment and the availability of THz sources with sufficient power.

A low-cost, compact THz system for imaging and spectroscopy can accelerate THz research and resolve more burning issues affecting our welfare. Our synergistic effort will bring advances in high-resolution imaging, material inspection for high value-added manufacturing, and food safety.
  • Research Impact
We have developed low-cost, high-power THz sources based on the scalable coupled oscillator-radiator array architecture implemented by 65-nm complementary metal-oxide-semiconductor (CMOS) technology. These chips comprise synchronized oscillators at the fundamental frequency with the desired harmonic signals radiating coherently for high output power.

Our second-harmonic chip operating at 0.45 THz incorporated with a low-cost Teflon lens yields the highest effective isotropic radiated power (EIRP) of 28.2 dBm. The 0.7-THz third-harmonic chip achieves the highest -3-dBm output power among all the coherent, scalable radiator Integrated Circuit (IC) beyond 0.6 THz.

We also developed beam steering chips at 0.32 THz with a scanning range of ±30º. These THz sources enable the replacement of the bulky waveguide-based setup feeding the THz antennas and devices we developed for THz Mueller matrix imaging and beam manipulation. We successfully demonstrated space-time-coding metasurface antenna s that can manipulate polarization, amplitude, frequency, beam direction, and phase of the antennas’ radiation through sequences of on-off switching of the meta-atoms. This disruptive technology provides new perspectives in imaging and communications. Although designed at 27 GHz for proof of concept, frequency scaling
of the antenna to THz frequencies can be achieved through CMOS technology.

Applications of THz technology are not limited to imaging and spectroscopy but also in the future 6th generation (6G) of wireless communications. We have developed THz-optic modulators to modulate THz signals into optical carrier frequencies efficiently. Therefore, the long-haul transmission of THz signals is made possible through optical communications networks. The fabricated thin-film lithium niobate modulator has a measured 3-dB electro-optic bandwidth of 170 GHz and a 6-dB bandwidth of 295 GHz. With further incorporation of mixers, amplifiers, etc., into our THz radiator ICs, the outputs of this project pave the way for our future demonstration of 6G wireless communications.