Fibre-Based Fast T-ray Tomography

Lead Research Organisation: University of Southampton
Department Name: Optoelectronics Research Centre

Abstract

The aim of this project is to demonstrate THz tomography, operating at millisecond image frame rates. We propose to design, build and characterise a fast multi-channel THz tomography system without moving parts, utilising a new THz source based on short-pulse fibre lasers driven by high-power laser-diodes. The output of the fibre lasers will be combined to produce THz emission by difference-frequency generation. The character of the THz emission from the proposed source allows inexpensive pyroelectric detector arrays to be used. A large number of THz measurement channels will be realised as a parallel and re-configurable data acquisition and processing electronic system. The breakthrough in speed and facility of THz tomography will be achieved via novel solutions in: fibre lasers; THz optical train (difference-frequency generation, beam conditioning, detector geometry); signal acquisition and processing; methods for image reconstruction. The proposed technology will also open the way to fast benchtop THz tomographs with applications in a wide area of science and engineering.We propose a demonstrator experiment which will employ this novel THz tomography system to map major species' concentrations and temperature field distributions in high-pressure flames. These flames are opaque to the usual IR analysis techniques because of scattering from the soot particles, but have been shown by the applicants to be transparent to THz radiation. In addition, many of the species in these flames exhibit absorption resonances in the THz region. THz tomography therefore promises to be the only way to study high pressure flames. This has important implications in our understanding of the combustion processes in, for example, aero engines with the possibility of improving efficiency and reducing emissions of greenhouse gases. We'll demonstrate at least the following performance in the case of high-pressure flames in the presence of soot: image frame acquisition period <1ms; maps of the cross-sectional distribution of major species with spatial resolution (in area) of D2/64; maps of distribution of temperature (T~1000K) of water molecules. This project is a direct consequence of the THz Basic Technology work funded by RCUK and combines established expertise in tomography (Manchester), THz technology (Leeds) and novel laser sources (Southampton). The synergy between the currently running Basic Technology THz work and this project will allow the identification of the spectral behaviour of the chemical species in the flame under realistic conditions and indicate the best choice of spectral lines for temperature mapping. The project is a crucial step towards THz tomography for imaging of gas mixture systems and a variety of other objects, with expected strong impact on the future utility and affordability of the THz technology.

Publications

10 25 50
 
Description During this project we developed a compact source of THz radiation based on the frequency mixing of the output of a two wavelength fibre laser source. We achieved high power narrow linewidth output in the approximate range 1-3THz with ~1 GHz linewidth. We developed a spectrometer based on this source and illustrated high resolution spectroscopy of water vapour in air.
Exploitation Route We undertook a project with an industrial sponsor (Samsung) on a medical application of the spectrometer developed. Unfortunately the results were inconclusive and we suffered source reliability issues that hindered further detailed study. We have parked this research for the present.
Sectors Aerospace, Defence and Marine,Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology,Security and Diplomacy

 
Description The work we undertook on this project stimulated the interest of Samsung, who placed a contract with us to explore the possibility of using narrow-linewidth THz radiation to manipulate proteins. The studies proved inconclusive in the end and the project was ultimately put on hold.
First Year Of Impact 2012
Sector Healthcare,Manufacturing, including Industrial Biotechology
Impact Types Societal

 
Description SAMSUNG Global Research Outreach Scheme
Amount £100,000 (GBP)
Organisation Samsung 
Sector Private
Country Global
Start 12/2012 
End 11/2013
 
Description SPI Lasers UK Ltd
Amount £80,000 (GBP)
Funding ID UOS08888 
Organisation SPI Lasers UK 
Sector Private
Country United Kingdom
Start 01/2013 
End 09/2013
 
Description TSB - Laser Based Manufacturing
Amount £320,000 (GBP)
Organisation Innovate UK 
Sector Public
Country United Kingdom
Start 10/2009 
End 10/2012
 
Description Collaboration on THZ source development and testing 
Organisation University of Leeds
Country United Kingdom 
Sector Academic/University 
PI Contribution Development of fibre based THZ source.
Collaborator Contribution Test of source and associated spectrometry trials on water vapour.
Impact Technical papers (see publication list).
Start Year 2009
 
Description Collaboration on THZ source development and testing 
Organisation University of Manchester
Country United Kingdom 
Sector Academic/University 
PI Contribution Development of fibre based THZ source.
Collaborator Contribution Test of source and associated spectrometry trials on water vapour.
Impact Technical papers (see publication list).
Start Year 2009
 
Description Royal Society Summer Exhibition 2008 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? Yes
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Demonstrated the impact of optical fibre technology in the internet and laser based manufacturing.

Large amount of PR
Press interviews
School children visits etc
Year(s) Of Engagement Activity 2008
URL https://royalsociety.org/summer-science/2008/