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

Lead Research Organisation: University College London
Department Name: Electronic and Electrical Engineering

Abstract

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.

Planned Impact

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.
 
Description We have demonstrated that THz frequencies are suitable for high data rate, short range wireless communications. In particular, we have shown by systems analysis and confirmed experimentally that atmospheric attenuation levels are acceptable for indoor wireless coverage systems.

We have made a proof of principle demonstration of THz spectroscopy with unprecedented resolution and frequency accuracy. At the start of the COTS Programme Grant, highly coherent (Hz linewidth) continuous wave THz sources did not exist. We started from heterodyning of phase-locked communications wavelength lasers in ultra-fast photodiodes to access the frequency range up to 2 THz. Higher frequencies were addressed using quantum cascade laser (QCL) technology.
A selection of achievements of the COTS Programme Grant include:
• Development of QCL self-mixing with the University of Queensland [1] [2] leading to new IP filings.
• Successful demonstration of photonically generated THz wireless signals at up to 100 Gb/s [3] [4], leading to an invited tutorial presentation at the 2014 IEEE/OSA Optical Fibre Communications Conference and an invited review in Nature Photonics [5].
• Successful demonstration of the first monolithically integrated dual DFB laser source and UTC device, with up to 100 µW generated at 120 GHz (through an international collaboration with III-V Laboratories) [6].
• Successful demonstration of the first locking of a THz QCL operating at 1.997 THz to a fibre-based comb source [Optics Letters, in preparation].
• Successful demonstration of coupled cavity Vernier effect tuned QCL [7].
• First demonstration of efficient out-coupling of QCL mode using hollow waveguide technology [8] [9].
A full publication list (> 250 papers and other information can be found on the COTS website www.terahertzsystems.org.
Added Value and use of Programme Grant Flexibility
Collaboration between the COTS consortium has enabled unique technologies to be developed, which could not have been developed otherwise. For example, the locked QCL capability was achieved using University of Leeds QCL with UCL photonic locking technology. The same technology was used to demonstrate ultra narrow linewidth spectroscopy capability using baseline FTIR measurements from University of Leeds and London Centre for Nanotechnology. Achieving these results required deployment of personnel and equipment resources between the consortium universities in a flexible manner. A further example is the use of UCL low-loss THz waveguide designs fabricated at the University of Cambridge and by international project partner Rutgers University to achieve coupling to samples in cryostatic environments. The COTS Programme Grant has also played a key role in the formulation of the successful UK THz Network proposal TeraNet (PI: Professor J. E. Cunningham) funded by EPSRC, and has led engagement with industrial and other end users through such activities as the successful THz Day, held at Cambridge University. Further, we have developed a set of outreach activities from exhibition at the science museum (Dr C. Renaud and Dr M. Fice) on the 19th of June 2014 in collaboration with the Photonics KTN and the Institute of Physics or a BBC radio broadcast explaining the use of QCL for THz techonology given by Professors E. Linfield and G Davies. COTS (Dr Fice) also presented an exhibition at the Big Bang Science Fair at Alexandra Palace. Finally in order to disseminate even further the importance of the THz part of the spectrum and developing technologies to access it a video was edited and published on youtube (https://www.youtube.com/watch?v=7FY5kbvBbic)


[1] P. Dean and al., Applied Physics Letters, vol. 103, p. 181112, 2013.
[2] A. Rakic and al., Optics Express, vol. 21, pp. 22194-22205, 2013.
[3] H. Shams and al., IEEE Photonics Journal, vol. 7, 2015.
[4] H. Shams and al., Optics Express, vol. 22, pp. 23465-123472, 2014.
[5] T. Nagatsuma, G. Ducournau and C. C. Renaud, Nature Photonics, vol. 10, pp. 371-379, 2016.
[6] F. Van Dijk and al., IEEE Photonics Technology Letters, vol. 26, pp. 965-968, 2014.
[7] I. Kundu and al., Optics Express, vol. 22, p. 16595-16605, 2014.
[8] F. Castellano and al., Optics Express, vol. 23, p. 5190-5200, 2015.
[9] R. Wallis and al., Optics Express, vol. 23, p. 26276-87, 2015.
Exploitation Route Short range wireless systems could be developed for high capacity connections between personal devices, such as smart-phones, tablets and lap-top computers and the fixed communications infrastructure.

Precision THz spectroscopy can be used for the analysis of molecular structure in substances of commercial interest. A new Programme Grant HyperTHz commenced in 2017 to develop THz instrumentation based upon COTS technologies.
Sectors Aerospace, Defence and Marine,Chemicals,Digital/Communication/Information Technologies (including Software),Electronics,Healthcare,Government, Democracy and Justice,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology,Security and Diplomacy

URL http://www.terahertzsystems.org
 
Description Demonstrations of high data rate wireless transmission carried out under this grant have increased interest in the use of THz frequencies for future wireless systems. The technology is now under active investigation by companies such as Huawei for use in 5G+ communications systems. The THz generation materials developed within the programme are supplied commercially to a major manufacturer of THz products. A patent, granted in 2015, relating to a high speed switch based on materials developed in the programme has been assigned to a major electronics company. A patent on THz bandwidth photodiodes using the technologies developed in the programme has been granted in the US and Japan. The technology is being evaluated by a major photonics manufacturer. A joint patent has been granted with an Australian university on a laser system for imaging and materials analysis and the technology is being developed for exploitation.
First Year Of Impact 2017
Sector Digital/Communication/Information Technologies (including Software),Electronics,Manufacturing, including Industrial Biotechology
Impact Types Societal,Economic

 
Description Collaborative Inpact studentship with National Physical Laboratory
Amount £100,000 (GBP)
Organisation University College London 
Sector Academic/University
Country United Kingdom
Start 11/2014 
End 10/2018
 
Description ESA Call on Millimeter wave high power source
Amount € 385,000 (EUR)
Funding ID 4000117914/16/NL/GLC 
Organisation European Space Agency 
Department European Space Research and Technology Centre (ESTEC)
Sector Public
Country France
Start 01/2017 
End 12/2019
 
Description FP7-ICT IPHOBAC-NG
Amount € 480,000 (EUR)
Funding ID 619870 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 11/2013 
End 10/2016
 
Description Collaboration with CityU Hong Kong on THz spectroscopic sensors 
Organisation City University of Hong Kong
Country Hong Kong 
Sector Academic/University 
PI Contribution Developoment of sensing techniques based on uni travelling carrier photodetectros based at UCL
Collaborator Contribution Development of an integrated spectroscopic tool for gas sensing
Impact The partnership is just starting so no outcome yet
Start Year 2016
 
Description Collaboration with Rutherford Appleton Laboratory and European Space Agency 
Organisation European Space Agency
Country France 
Sector Public 
PI Contribution Development and design of high power high speed photodetectors, to be used as millimetre wave optically pumped oscillators
Collaborator Contribution ESA is funding the work while STFC-RAL is developing the packaging and modelling heat management.
Impact So far we have demonstrated a lower bias high performance high speed photodetector.
Start Year 2016
 
Description Collaboration with Rutherford Appleton Laboratory and European Space Agency 
Organisation Rutherford Appleton Laboratory
Country United Kingdom 
Sector Public 
PI Contribution Development and design of high power high speed photodetectors, to be used as millimetre wave optically pumped oscillators
Collaborator Contribution ESA is funding the work while STFC-RAL is developing the packaging and modelling heat management.
Impact So far we have demonstrated a lower bias high performance high speed photodetector.
Start Year 2016
 
Description Big Bang schools event - Alexandra Palace 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Presented research-inspired interactive exhibits as part of the BIg Bang schools event aimed at increasing the interest and engagement of (mainly) secondary school children in science and engineering. Held at Alexandra Palace, London.
Year(s) Of Engagement Activity 2014
 
Description Big Bang schools event - Newham College 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Presented research-inspired interactive exhibits as part of the BIg Bang schools event aimed at increasing the interest and engagement of (mainly) secondary school children in science and engineering. Held at Newham College, London, 30 June 2015.
Year(s) Of Engagement Activity 2015
 
Description Big Bang schools event - Westminster Kingsway College 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Presented research-inspired interactive exhibits as part of the BIg Bang schools event aimed at increasing the interest and engagement of (mainly) secondary school children in science and engineering. Held at Westminster Kingsway College, London on 1 July 2015.
Year(s) Of Engagement Activity 2015
 
Description KTN Photonics group book launch at Science Museum 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Interactive tabletop display related to photonic THz systems to help illustrate the range of photonics applications being investigated in the UK. Part of the launch of the Photonics - Revolutionising Our World publication by the Photonics group of the Knowledge Transfer Network on behalf
of the UK photonics community and the Photonics Leadership Group. Evening event held at the London Science Museum on 19 June 2015, reaching over 200 people from postgraduate students to policymakers.
Year(s) Of Engagement Activity 2014
 
Description Photonics Open Day 2015 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact UCL hosted a Photonics Open Day to coincide with the International Year of Light. Over 70 school children (6th form students from across the region) visited the London Centre for Nanotechnology and the Electronic and Electrical Engineering Department where they heard talks about photonics and terahertz. This coincided with the International Year of Light 2015.
Year(s) Of Engagement Activity 2015
 
Description Physics at work 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Physics at work takes place every year at the Cavendish Laboratory. A total of 2000 school students visit to listern to talks and demonstrations. My research group gives around 20 presentations to 25 students each year about semiconductor physics.

Heightened interest in science and particular physics amongst local school students. Physics undergraduates are currently at record numbers in Cambridge.
Year(s) Of Engagement Activity Pre-2006,2006,2007,2008,
URL http://www-outreach.phy.cam.ac.uk/physics_at_work/
 
Description Royal Society's 'Quantum of Spin' Summer Science Exhibition 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact High profile exhibition about quantum technologies with links to photonics and terahertz research at UCL particularly highlighted.
Year(s) Of Engagement Activity 2012
 
Description Short Course to CityU student in Hong Kong on THz coherent photonic systems 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Special lecture for all Hong Kong postgraduate students in technology and Physics as part of a workshop on advanced technology at CityU. expected attendance is 80
Year(s) Of Engagement Activity 2016
 
Description UK Terahertz Day - Lobbying for the formation of a UK THz Network funded by the EPSRC 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact 80 academic and industry guests attended the UK's first Terahertz Day workshop/conference event at Cambridge. There were keynote talks on terahertz activity from companies such as Teraview and then each of the major THz research labs in the UK highlighted their work with a view to set up new collaborations and lobby for the creation of a THz Network group funded by the EPSRC. This was successfully set up and is lead by Professor John Cunningham (Leeds).
Year(s) Of Engagement Activity 2013
URL http://gow.epsrc.ac.uk/NGBOViewGrant.aspx?GrantRef=EP/M00306X/
 
Description Video for schools: "Exploring the Last Frontier of the Electromagnetic Spectrum" 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Schools
Results and Impact We produced a video with involvement from Investigators and RAs on COTS aimed at educating school children about the importance of THz, photonics and engineering more generally, particularly in the International Year of Light 2015. The video is available at: https://youtu.be/7FY5kbvBbic. To date, the video has had over 300 Youtube views.
Year(s) Of Engagement Activity 2015
URL https://youtu.be/7FY5kbvBbic