All-Semiconductor Integrated Terahertz Time Domain Spectrometer

Lead Research Organisation: University of Southampton
Department Name: School of Physics and Astronomy


The terahertz (THz) part of the EM spectrum stands between infrared and microwaves. Therefore, THz technology stands in the interface of optics and electronics; until recently, both electronics and optics technological approaches failed to produce a practical THz source or detector. THz sources and detectors were prohibitingly expensive and as a consequence were used only in astronomy and physics research. This is the reason why traditionally this spectral region was called the THz gap. Although there was a lot of interest for medical diagnosis and material spectroscopy because this region is very rich in absorptions, practical applications were not possible. However, THz science expanded during the 1990s with the invention of ultrafast laser systems that can be used to generate and measure THz fields. The instrument that redefined THz science is called Terahertz time domain spectrometer (THz-TDS). At present, companies such as Teraview Ltd. target the development of imaging solutions and produce spectrometers with advanced capabilities in drug research and medical diagnosis but also with high cost and size. It is obvious though that research in the area should be sponsored to expand outside this approach of complicated spectroscopic imaging machines to a more flexible compact solution that will open even more application possibilities. THz spectrometers need further development to unleash their full market potential; mainly, development to bring the cost and size down. Furthermore THz radiation is strongly absorbed by water and this makes it impossible to use THz to penetrate the human body or make measurements of liquids; this limitation should be overcome. Nevertheless, THz cancer detection is specifically based on the sensitivity of THz on water content; a THz spectrometer can detect the higher water concentration of cancerous cells. Scientists are addressing these problems daily, doing research for smaller size spectrometers and liquid measurement ability; it is generally accepted that there is a place for Terahertz technology in the near-future of sensing for medicine, biology and homeland security.The research proposed here is crucial to further expand terahertz technology and it results to a device that can be directly used in the industry with solid and liquid sample capabilities. It is a highly interdisciplinary attempt to give a new route for the use of this technology in chemistry, medicine and biology. The proposed research is for an integrated THz time domain spectrometer in an all-semiconductor configuration. It aims to the development of a terahertz spectrometer with reduced cost and size by using compact semiconductor pump laser sources and integrated optics. Furthermore, it overcomes the water absorption problem because it uses very small water samples to keep absorption values low. This research is timely because at the moment terahertz industry is coming to maturity commercially around the world as it is slowly adopted in the pharmaceutical industries and is tested also for medical diagnosis and security controls.
Description During this grant we have created a THz - VECSEL spectrometer. We have also worked on the performance of VECSELs.
Although VECSELs were exhibiting adequate power levels and short pulses they could not demonstrate adequate stability in order to start implementing the integrated spectrometer that was promised at the beginning. We have worked a lot in the grant in producing VECSELS that have the necessary stability to be used for a THz time domain apparatus and we believe that now VECSELs could be used for that. Also we have worked on algorithm to study materials in the THz spectrometer that we believe that is a field that has not been adequately studied and is a major obstacle on the use of THz spectrometers. We have made our algorithm freely available in
Exploitation Route As Vecsels improve a THz - VECSEL spectrometer is the way forward for a compact and fast spectrometer to be used in the field
Sectors Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software),Electronics,Manufacturing, including Industrial Biotechology

Description In Laser research, bringing VECSEL semiconductor lasers closer to maturity we have helped subsequent research efforts to improve the performance of VECSELS. Also during the award we have worked a lot on THz algorithms for material THz parameter extraction that have been used by other groups and we have published a book chapter on how to produce a THz refractive index algorithm based on transfer functions. We have freely included our algorithm in
First Year Of Impact 2014
Sector Aerospace, Defence and Marine,Electronics,Other
Impact Types Cultural,Economic

Title THz material parameter extraction alorithm 
Description Algorithm that is freely available on extracting refractive indices from data taken with THz time domain spectrometers 
Type Of Material Computer model/algorithm 
Year Produced 2013 
Provided To Others? Yes  
Impact not known, people are using the algorithms but i do not know if something has been published 
Description Cavendish Cambridge 
Organisation University of Cambridge
Department Cavendish Laboratory
Country United Kingdom 
Sector Academic/University 
PI Contribution The collaboration is based on the growth of samples in Cavendish and our use for fabrication of emitters, lasers etc
Collaborator Contribution Molecular beam epitaxy
Impact The publications that we got together
Start Year 2010
Description Teraview 
Organisation Teraview Ltd
Country United Kingdom 
Sector Private 
PI Contribution We have worked with TeraView on two KTS secondments on using outputs of our research mainly on THz refractive index algorithms to problems encountered by TVIiew
Collaborator Contribution Advice, in kind contribution of a Tsunami spectra Physics Laser, with pump and pulse picker
Impact General collaboration, transfer of knowledge
Start Year 2010