• Project Abstract
The THz region was limited to applications in radio astronomy and space science. In recent years, THz systems have expanded into many more areas of science, defence, security, and non-destructive industrial applications. Microwave based THz cameras have demonstrated the highest sensitivity at large distances. However, their current state of the art is comparable to the first analog photographic cameras characterized by long exposition times. Two fundamental problems have to be addressed to change this situation: technologically, there is the lack of integrated coherent arrays with high power and sensitivity; and theoretically, a field representation to characterize analytically these systems is missing.
I propose to tackle the technological problem by exploiting the coherency between small lens antenna arrays coupled to actuated lenses to overcome the sensitivity problem. The proposed antenna technology is based on a recent breakthrough that I pioneered: micro-lenses excited by leaky waves with seamless integration in silicon technology. This antenna enables the fabrication of large fly’s eye cameras in just two wafers, and promises one order of magnitude better scanning performances than previous solutions. An analytical model to investigate the electromagnetic response of coherent THz arrays is the enabling tool for optimizing the camera performances. I will develop this tool by combining advance spectral antenna techniques with coherent
Fourier Optics. This model will not only be used in new beamforming techniques, but also for the characterization of future THz telecommunication links.
This project will make the first significant strides in developing the next generation of coherent THz imaging cameras. The outcome of this project will be instrumental in pushing today's costly THz niche applications into the main stream, and possibly pole vault THz systems into the 21st century communication society.
• Project Conclusions
We have developed a theoretical framework based on Coherent Fourier Optics for deriving the Plane Wave Spectrum in Quasi-Optical Systems. This technique is extremely powerful for the optimization of these systems using field-match techniques as well for modelling periodic structures inside Quasi-Optical systems. The most relevant contributions that came out thanks to this framework and that would have not been possible otherwise are:
• We derived the fundamental trade-offs for absorber based focal plane arrays and compared to well-known antenna trade-offs. These trade-offs were applied to the design of THz imaging security systems
•We developed state-of-art wide-band integrated lens antennas exploiting the field match between the QO field and the field radiated by a leaky wave antenna, including also the complex field propagation through in-lens periodic gratings
•We designed focal plane arrays based on lens antennas with state of the art scanning performance for imaging applications.
Besides the theoretical framework, we performed the following key technological demonstrations that enable the efficient exploitation of the THz spectrum for future application areas in sensing and communications:
• Dynamic beam steering of ultra-narrow beams at >100GHz via phased arrays composed of leaky wave lens antennas integrated with piezo-motors
• CMOS integrated focal plane array based on leaky wave connected arrays for diffraction limited imaging in the 200-600GHz bandwidth.
• Photoconductive antennas with leaky wave enhanced radiation fabricated on a micro-metric LT-GaAS membranes for power generation and detection in the 100GHz-1THz bandwidth.
