Periodic Reporting for period 1 - THEMIS (Development of a Terahertz Self-Mixing Imaging System)
Reporting period: 2017-01-01 to 2018-06-30
During the ERC Advanced Grant ‘TOSCA’ (N° 247375), a very different approach was taken to THz generation, focused on the use of a small, compact, semiconductor source – the THz frequency quantum cascade laser (QCL), which was first demonstrated in 2002. A key breakthrough occurred in 2011 when my group in Leeds demonstrated, in collaboration with the University of Queensland, that it is possible to use a single QCL device as both a high power source of THz radiation, and also as a phase sensitive detector in a ‘self-mixing’ scheme. We subsequently made considerable advances to this technology, including not only the development and demonstration of new imaging modalities, but also the verification of the applicability of our technology across a range of application areas including non-destructive testing, materials analysis and biomedical imaging. This included measuring doped semiconductor samples, identifying explosives, and classifying different types of biological tissue. We had also developed techniques for swept-frequency feedback interferometry, three-dimensional imaging, and inverse synthetic aperture radar imaging.
Notwithstanding this potential, a number of developments were necessary to translate this technology to industry and other non-academic end-users – these were the focus of this proposal – Themis (N° 727451). They included: (a) the development of a portable optical-breadboard-based self-mixing imaging system, moving away from the existing laboratory-based optical-bench-top apparatus; (b) the demonstration of the technology in the field both with commercial end-users, and at conferences/workshops/trade shows; and, (c) the evaluation of new opportunities for THz self-mixing imaging, together with identification of end-user applications.
The project was highly successful. A portable imaging system was developed, and demonstrated at the UK’s Knowledge Transfer Network (KTN)’s ‘Showcasing Emerging Technologies 2018 – Photonics and Imaging’ in London, with terahertz research and its applications being discussed at the Innovate UK's KTN 2018 ‘Materials Research Exchange & Investor Showcase’ in London. The self-mixing imaging system was adapted to enable gas spectroscopy, incorporating a gas cell into the experimental geometry, and broad range of samples were tested with a specific focus on materials of relevance to the Electronics and Medical sectors. Further evaluation of the terahertz market was also undertaken, and a range of high performance THz QCLs were developed, operating over a range of frequencies, providing greater opportunities to potential end-users.
In part as a result of this success, further national funding was received from the UK’s Engineering and Physical Sciences Research Council, through a £6.5M Programme Grant ‘HyperTerahertz’ with University College London and the University of Cambridge to develop a breadth of terahertz instrumentation, including self-mixing imaging and near-field microscopy.