Terahertz Frequency Detection and Identification of Materials and Objects

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1 Terahertz Frequency Detection and Identification of Materials and Objects

2 NATO Science for Peace and Security Series This Series presents the results of scientific meetings supported under the NATO Programme: Science for Peace and Security (SPS). The NATO SPS Programme supports meetings in the following Key Priority areas: (1) Defence Against Terrorism; (2) Countering other Threats to Security and (3) NATO, Partner and Mediterranean Dialogue Country Priorities. The types of meeting supported are generally "Advanced Study Institutes" and "Advanced Research Workshops". The NATO SPS Series collects together the results of these meetings. The meetings are coorganized by scientists from NATO countries and scientists from NATO's "Partner" or "Mediterranean Dialogue" countries. The observations and recommendations made at the meetings, as well as the contents of the volumes in the Series, reflect those of participants and contributors only; they should not necessarily be regarded as reflecting NATO views or policy. Advanced Study Institutes (ASI) are high-level tutorial courses intended to convey the latest developments in a subject to an advanced-level audience Advanced Research Workshops (ARW) are expert meetings where an intense but informal exchange of views at the frontiers of a subject aims at identifying directions for future action Following a transformation of the programme in 2006 the Series has been re-named and re-organised. Recent volumes on topics not related to security, which result from meetings supported under the programme earlier, may be found in the NATO Science Series. The Series is published by IOS Press, Amsterdam, and Springer, Dordrecht, in conjunction with the NATO Public Diplomacy Division. Sub-Series A. Chemistry and Biology Springer B. Physics and Biophysics Springer C. Environmental Security Springer D. E. Information and Communication Security Human and Societal Dynamics IOS Press IOS Press Series B: Physics and Biophysics

3 Terahertz Frequency Detection and Identification of Materials and Objects edited by R.E. Miles University of Leeds, U.K. X.-C. Zhang Rensselaer Polytechnic, Troy, U.S.A. H. Eisele University of Leeds, U.K. and A. Krotkus Semiconductor Physics Institute, Vilnius, Lithuania Published in cooperation with NATO Public Diplomacy Division

4 Proceedings of the NATO Advanced Research Workshop on Terahertz Frequency Detection and Identification of Materials and Objects Spiez, Switzerland 7 11 July 2006 AC.I.P. Catalogue record for this book is available from the Library of Congress. ISBN (PB) ISBN (HB) ISBN (e-book) Published by Springer, P.O. Box 17, 3300 AA Dordrecht, The Netherlands. Printed on acid-free paper All Rights Reserved 2007 Springer No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission from the Publisher, with the exception of any material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work.

5 CONTENTS Organising Committee Sponsors Preface ix x xi Theme 1: Devices Terahertz Emission from Semiconductors Excited by Ultrafast Laser Pulses A. Krotkus, R. Adomavičius, and V. L. Malevich Terahertz Generation by Multiplication Jan Stake, Tomas Bryllert, T. Arezoo Emadi, and Josip Vukusic Towards Superlattice Terahertz Amplifiers and Lasers Alvydas Lisauskas, Ernst Mohler, Hartmut G. Roskos, and Nataliya V. Demarina Tailoring the Emission of Terahertz Quantum Cascade Lasers Richard Green, Lukas Mahler, Cosimo Mauro, Tonia Losco, Ji-Hua Xu, Alessandro Tredicucci, Fabio Beltram, Harvey Beere, and David Ritchie Guided Propagation of Terahertz Pulses on Metal Wires Kanglin Wang and Daniel M. Mittleman Superlattice and Other Negative-Differential-Resistance Devices: Current Status Heribert Eisele Theme 2: Interactions with Materials Molecular and Organic Interactions A. G. Davies and E. H. Linfield 91 v

6 vi CONTENTS Terahertz Beam Interactions with Amorphous Materials Mira Naftaly and Robert E. Miles Development of Tagless Biosensors for Detecting the Presence of Pathogens Jing Yin Chen, Joseph R. Knab, Shuji Ye, Yunfen He, and Andrea G. Markelz Theme 3: Detection and Sensing Improvements to Electronic Techniques for Terahertz Spectroscopic Detection Daniel W. van der Weide, Alan D. Bettermann, Min K. Choi, and John Grade Terahertz Time-Domain Spectroscopy of Crystalline and Aqueous Systems Peter Uhd Jepsen, Hannes Merbold, Zhengxin Li, Xiaoyu Xing, and Stewart Clark Continuous-Wave Terahertz Photomixer Systems for Real-World Applications Ian S. Gregory, Hideaki Page, and Lee Spencer Theme 4: Systems for Security Systems Requirements for A Multi-Channel Terahertz Contraband Scanner William S. Truscott Challenges to Terahertz Counter-Terrorism and Security-Related Applications Howard Cummins Terahertz Detection of Illegal Objects Roger Appleby, Peter R. Coward, and Gordon N. Sinclair Terahertz Rays to Detect Drugs of Abuse Kodo Kawase, Adrian Dobroiu, Masatsugu Yamashita, Yoshiaki Sasaki, and Chiko Otani

7 CONTENTS Terahertz Spectroscopy for Explosive, Pharmaceutical, and Biological Sensing Applications Hai-Bo Liu and Xi-Cheng Zhang Terahertz Communications: A 2020 vision Martin Koch vii Theme 5: Overview Applied Terahertz Science: The Technology of the Future, and Always Will Be? Martyn Chamberlain List of speakers List of participants Group photograph Index

8 ORGANISING COMMITTEE Professor X.-C. Zhang (Rensselaer Polytechnic, USA) Professor A. Krotkus (Semiconductor Physics Institute, Vilnius, Lithuania) Professor R. E. Miles (University of Leeds, UK) Dr. H. Eisele (University of Leeds, UK) Co-director Co-director Secretary Treasurer ix

9 We wish to thank the following for their financial contributions which have contributed greatly to the success of the workshop. NATO US Army International Technology Centre Atlantic, Research Division US Air Force Office of Scientific Research Teranova (European Union Integrated Project) x

10 PREFACE This volume contains an account of the third NATO-sponsored meeting on terahertz science and technology. The first, held in 1996, was an Advanced Study Institute (ASI) on New Directions in Terahertz Technology which in turn was followed in 2000 by an Advanced Research Workshop (ARW) entitled Terahertz Sources and Systems. In these earlier meetings, the difficulties involved in generating THz frequency signals formed a background to most of the presentations and discussions with frequent mentions of the 0.3 to 3 THz Terahertz Gap. This gap is still with us but, with advances in technology, has been reduced to the region between about 1.0 THz and 2.5 THz. In the 2000 ASI, the lack of a complete set of THz electronic devices, in particular an amplifier, was identified as an obstacle to progress. While this is still the case, it became clear from this ASI that THz amplifiers based on semiconductor superlattice structures are very close to being realized. The purpose of this workshop was to explore the potential of THz techniques in the detection of illegal substances, especially for security purposes. The workshop set out to identify the state of the art, to define the scope of the problem and the areas where THz frequency radiation could contribute. Extensive studies have shown that drugs of abuse and explosives can be identified from their THz spectra and prototype systems are already in place in Japan to scan mail online as it passes through the automated systems. From this and other work reported at the ASI it is clear that THz technology has a part to play in security screening but developments are still required to improve the delivery of THz signals to the area of concern and its subsequent detection. One possibility is that THz techniques may not be the first line of detection but could be used for more detailed identification of, say, suspicious packages. Stand-off detection, as is required in the identification of suicide bombers, is a more difficult issue but the delegates concluded that detection at 30 m is possible but effective systems will only result from close cooperation between the THz generation and signal-processing communities. We learned at this meeting that THz radiation can be generated at a distance using air as the transducer. However, this necessitated the use of a powerful laser beam which could not be employed in a public place such as an airport, but could perhaps be implemented in other situations. We trust that the readers of this book will gain a flavour of the excitement of the meeting. However, one thing that is difficult to convey here is the wonderful way in which we were looked after by our hosts Peter and Margit Schlatter for whom nothing was too much trouble. xi

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