COherent Terahertz Systems (COTS)-opening up the terahertz spectrum for widespread application

The terahertz (THz) frequency region within the electromagnetic spectrum, covers a frequency range of about one hundred times that currently occupied by all radio, television, cellular radio, Wi-Fi, radar and other users and has proven and potential applications ranging from molecular spectroscopy through to communications, high resolution imaging (e.g. in the medical and pharmaceutical sectors) and security screening. Yet, the underpinning technology for the generation and detection of radiation in this spectral range remains severely limited, being based principally on Ti:sapphire (femtosecond) pulsed laser and photoconductive detector technology, the THz equivalent of the spark transmitter and coherer receiver for radio signals. The THz frequency range therefore does not benefit from the coherent techniques routinely used at microwave/optical frequencies. Our programme grant will address this. We have recently demonstrated optical communications technology-based techniques for the generation of high spectral purity continuous wave THz signals at UCL, together with state-of-the-art THz quantum cascade laser (QCL) technology at Cambridge/Leeds. We will bring together these internationally-leading researchers to create coherent systems across the entire THz spectrum. These will be exploited both for fundamental science (e.g. the study of nanostructured and mesoscopic electron systems) and for applications including short-range high-data-rate wireless communications, information processing, materials detection and high resolution imaging in three dimensions.

The proposed work is focused on the goal of enabling the THz part of the electromagnetic spectrum to be accessed with the same precision that can be achieved at radio and, increasingly, optical frequencies. We envisage that this will enable important scientific, commercial and societal benefits.

Considering scientific benefits, the development of coherent THz spectroscopy using simple source/detector modules will have great impact in many areas of research. For example, many more 'labels', including low lying vibrational states as well as spin states split by larger fields, will be useable for determining the structural and dynamical parameters of proteins. On the physical sciences side, using coherent THz radiation will allow measurement and manipulation, including the creation of coherent superpositions, of quantum states (in e.g. single electron transistors) separated by energies of order tens of Kelvin, implying much less stringent cooling requirements than demanded currently for microwave-based state manipulation. This capability would be valuable for quantum information processing research. We are already involved in collaborations with museums and galleries, where the capability of THz imaging to study underlying layer structure in paintings and glazes has revealed details of considerable historical interest.

Concerning commercial benefits, the work on ultra-wideband wireless would enable the creation of wireless devices having similar information transfer rates to those available from direct fibre connections. This represents a significant (> $1b based on conventional system sales) [Infonetics] market opportunity. The work on spectroscopy and sensing will enable the production of small footprint (lab bench-based) CW microwave-->THz spectrometers for routine analysis needs in clinical labs and in pharmaceutical production, as well as stand-off detection sytems for use in security applications. Finally, the new coherent imaging capabilities envisaged will be of value in areas from security scanning to clinical imaging of cancerous tissue to determine surgical margins. These are again expected to be large (> $0.5b, with 37% annual growth rate by 2018 [BCC Research]) markets.

Concerning societal benefits, we anticipate that the population will welcome the availability of much increased data rates from their wireless devices and the increasing interactivity that will result. There has been considerable concern about radiation exposure from whole body X-ray security scanners and the use of THz scanners with their benefit of non-ionizing radiation will, we consider, be welcomed. Societal benefits through better security and crime detection using THz sensing and spectroscopy, will also accrue. Improvements to healthcare through compact tools for clinical imaging and pharmaceutical testing will constitute further societal benefits. Finally, we see cultural benefits through work using THz imaging to learn more about the creation of works of art.

In order to ensure that these benefits will be realised we have set up a range of partnerships with key industries and users, to contribute their knowledge of applications requirements and to provide exploitation routes for the technologies developed. As well as traditional knowledge transfer routes, such as demonstrators, publication, spin-outs and IP licensing we expect that transfer through the provision of highly trained researchers from the Programme to beneficiaries will be a major feature of our work.

We anticipate that the benefits outlined above will be achieved within five years of the completion of this grant.

In addition to the beneficiaries identified above, the knowledge gained through the project is likely to enable us to engage with businesses operating in related areas through collaboration or consultancy. Here, the role of project partner BNC is of special importance.