A DSTO workshop at the frontier of technology, Dec 16-17, 2004, Adelaide, Australia.

TeraHertz for Defence and Security

  Abstract Listing  


Invited Oral Presentations: (listed in alphabetical order of presenting author)


Author: Roger Appleby

Title: "From passive millimetre wave to THz for security applications."

Affiliation: QinetiQ, St. Andrews Rd, Gt. Malvern, Worcs, WR14 3PS, UK.

Abstract: It is well known that millimetre wave systems can penetrate poor weather, dust and smoke far better than infrared or visible systems. Imaging in this band offers the opportunity to be able to navigate and perform surveillance in these conditions of poor visibility. Furthermore the ability to penetrate dielectrics such as plastic and cloth has opened up the opportunity of detecting weapons and contraband hidden under people's clothing. The optical properties of materials have a direct impact on the applicability of imaging systems. In the terahertz band, solids exhibit absorption that can be assigned to vibrational modes. Lattice modes occur at the lowest frequencies and polythene for example has a lattice mode at 2.4THz. Solids have no such absorption in the millimetre bands (30 to 300GHz) and image contrast is produced by differences in transmission, reflection and absorption.

A novel, real time, mechanically scanned, passive millimetre wave imager has been designed. The antenna elements are based on a combination of a Schmidt camera and a conical scanner, both of which have their origins in optical systems. Polarisation techniques, which were developed for operation in the centimetric band, are used to fold the optics. Both 35GHz and 94GHz versions have been constructed.


Authors: R. Appleby, R. N. Anderton, S. Price, N. A. Salmon, G. N. Sinclair, P. R. Coward, A.R. Barnes, P. D. Munday, M. Moore, A. H. Lettington, and D. A. Robertson.

Title: "Mechanically scanned real time passive millimetre wave imaging at 94 GHz."

Affiliation: QinetiQ, St Andrews Road, Malvern, Worcs, WR14 3PS, UK.

Abstract: It is well known that millimetre wave systems can penetrate poor weather and battlefield obscurants far better than infrared or visible systems. Thermal imaging in this band offers the opportunity for passive surveillance and navigation allowing military operations in poor weather.

We have previously reported a novel real time mechanically scanned passive millimetre wave imager operating at 35 GHz and in this paper a 94 GHz variant will be described. This 94 GHz imager has a field-of-view of 30° x 60° and has diffraction limited performance over the central two thirds of this field-of-view. It is relatively inexpensive, because the scene is imaged using a linear array of direct detection receivers and compact folded optics. The receiver array has been constructed using indium phosphide monolithic microwave integrated circuits (MMICs) allowing high gain and low noise figure to be achieved. The compact optics consist of a polarisation sensitive mirror and a Faraday rotator. The mirror is constructed from expanded polystyrene supporting a printed copper grid etched onto a PTFE/glass fibre substrate these materials are low cost and readily available. The Faraday rotator is made from a commercial grade plasto-ferrite sandwiched between antireflection coatings. The optics produce a conical scan pattern and image processing is used to generate a raster scan pattern and to do gain and offset corrections.


Authors: Sandra G. Biedron, N. Gopalsami, J.W. Lewellen, S.V. Milton, J. Schneider, L. Skubal, M. Virgo (Argonne National Laboratory, USA), Gian Piero Gallerano, Andrea Doria, Emilio Giovenale, Giovanni Messina, Ivan Panov Spassovsky (ENEA C.R. Frascati, Frascati, Roma).

Title: "The use of terahertz radiation for global homeland security: focus on compact electron beam based sources."

Affiliation: Argonne National Laboratory, Advanced Photon Source, 9700 S. Cass Ave., Argonne, Illinois,
60439, USA.

Abstract: Although terahertz (THz) radiation was first observed about one hundred years ago, this portion of the electromagnetic spectrum at the boundary between the microwaves and the infrared has been, for a long time, rather poorly explored. This situation changed with the rapid development of coherent THz sources such as solid state oscillators, quantum cascade lasers, optically pumped solid state devices, and novel free electron devices. These in turn have stimulated a wide variety of applications from material science to telecommunications, from biology to biomedicine. In this talk, the focus will be on the production of THz radiation from electron beams. An overview of the present electron beam devices able to produce THz radiation and the corresponding output photon beam characteristics will be provided. Finally, a number of potential global homeland security uses will be given.


Authors: Trevor Bird, Kieran Greene, John Kot and Stephen Hanham.

Title: "Terahertz imaging from a RF engineering perspective."

Affiliation: CSIRO ICT Centre, POB 76, Epping, NSW 1710, Australia.

Abstract: The CSIRO ICT Centre has recently commenced a project to develop a terahertz (THz) wave imaging system, although capabilities relevant to future security, communications, sensing, actuation and spectroscopy will also be investigated. The project will build on CSIRO expertise in radio frequency (RF) engineering, including previous work in the millimetre-wave region, and medical imaging. The proposed application is low-cost medical imaging and will employ focal plane array technology to form the image. The intention is to build a benchtop demonstrator and to use this to investigate different medical applications. The demonstrator will be designed to confirm theoretical designs and understanding of the governing rules for propagation in biological and other media, demonstrate the potential to user groups, and to gain experience in the practicalities of system operation.

The presentation will outline the project and our proposed approach, which is from a RF engineering standpoint. This compares with some existing approaches that down-convert from the optical spectrum. The likely advantages of an RF approach are reduced size, greater efficiency and lower cost of the final imaging system. The technical challenges expected in realising the benchtop demonstrator include sensitivity of THz detectors, the power, complexity and cost of THz emitters, the realisation of multi-element arrays at THz, fabrication and integration, and losses in components. We do not expect to solve these problems alone but plan to partner with other organisations with complementary research goals.


Authors: B. Ferguson, S. Wang, D. Gray, X.-C. Zhang, and D. Abbott.

Title: "Towards the realisation of three-dimensional THz inspection systems."

Affiliation: Tenix Defence, 2nd Avenue, Technology Park, Mawson Lakes, SA 5095, Australia.

Abstract: A three-dimensional spectroscopic imaging system has many potential applications in defence and security settings, particularly for package and personnel inspection. This paper describes progress towards 3D THz inspection systems on two fronts; classification algorithms and tomographic imaging.

A classification algorithm based on frequency selection by a genetic algorithm is used to attempt to differentiate between materials in THz spectral images. Encouraging preliminary results have been obtained distinguishing Bacillus thuringiensis from benign powders, and detecting cancerous cells.

Coherent T-ray tomography has been used to obtain high fidelity reconstructions of 3D objects with sub-millimetre resolution. Reconstruction algorithms and example images will be presented.


Authors: Bernd M. Fischer, Matthias Hoffmann, Hanspeter Helm, and Peter Uhd Jepsen.

Title: "Chemical recognition with broadband THz spectroscopy and its applications in the defence and security sectors. "

Affiliation: Freiburg Materials Research Center, University of Freiburg, Stefan-Meier-Strasse 21, D-79104 Freiburg, Germany.

Abstract: THz science is developing rapidly in Europe as well as the rest of the world. There is strong interest in the exploitation of the THz frequency range in virtually all fields of basic natural science (physics, chemistry, biology) as well as medicine. Recently commercial interest in THz technology has also been growing, spurred by the potential for THz technology in the safety/security sector and biotechnology sector.

We will review some of the most important contrast mechanisms, which may lead to important real-world applications of THz technology, especially in the fields of applied chemistry and biotechnology. Whereas single-frequency THz technology without doubt will be important for e.g. real-time imaging at larger stand-off distances, we will concentrate on broadband spectroscopic identification of various substances. It has been established that the 0.1–4 THz spectral range contains a unique fingerprint of crystalline substances, including explosives and illicit drugs as well as most other chemicals in powder form. Since many packing materials are transparent to THz radiation this fundamental property of crystalline compounds, in principle, allows remote sensing and recognition of the chemicals. However, due to the enormous number of known (and still unknown) chemicals there are fundamental limitations to this recognition potential.

On the other hand, the THz spectrum of amorphous systems, including aqueous solutions, contains very little information about the detailed composition of the system. However, under certain conditions it is still possible to learn a great deal about amorphous systems with broadband THz spectroscopy. Amorphous systems of great biotechnological importance include DNA and proteins, both in aqueous solution and as dried matter. We will discuss methods for THz science and technology to attack the very complex problems involved in the extraction of useful new information, which may be difficult, expensive, or impossible to obtain with other methods, from minute amounts of biomaterial.


Authors: Anthony Fitzgerald, Colin Baker, Vincent Wallace, Emma Pickwell, Yoachun Shen, Thomas Lo, Bryan Cole, Phil Taday, William Tribe, Mike Kemp.

Title: "Terahertz reflection spectroscopy in security and biological applications."

Affiliation: TeraView Limited, Platinum Building, St. John's Innovation Park, Cambridge, CB4 0WS, UK.

Abstract: One of the key advantages of using THz wavelengths for security applications is that spectral fingerprints can be exploited to identify and characterise materials. Techniques for transmission measurements to identify these fingerprints are well advanced. The implementation of THz technology in many real-world security applications will, however, rely on identification of these features using reflection measurements. We show, for the first time, THz spectral measurements on the explosive material RDX measured in a reflection arrangement, with good agreement to results obtained in transmission.

Threat detection will be most useful when it is performed at some stand-off distance from the person concealing the potential hazard. We have developed a prototype system with the ability to make spectroscopic reflection measurements of objects some distance away. The performance of the system was validated using well characterised materials with flat responses in the THz regime (quartz, polyethylene and silicon). We demonstrate the ability of this stand-off system to detect spectral fingerprints of RDX in plastic explosive, at a distance of 1m. This is the first time that spectral measurements of explosive materials have been made at any significant stand-off distance.

We have also pioneered a hand-held spectroscopic reflection ‘wand’, with a single source and multiple detectors, which will be operated much like a metal detector at security checkpoints and is designed to detect explosives and weapons concealed beneath clothing. We present initial results from a prototype of this spectroscopic wand, showing spectroscopic discrimination between different materials. Spectroscopic measurements in reflection geometry can be used for chemical mapping. As a demonstration of this we apply Component Spatial Pattern Analysis (CSPA) to image scenes containing RDX, sucrose and lactose. CSPA successfully distinguishes the hazardous RDX material from the benign lactose and sucrose items, highlighting the potential benefits of using THz technology in the security field.

The techniques we have developed for security applications should benefit other areas of research, including medical applications. We have shown there is a difference in the spectral response of normal skin and skin with basal cell carcinoma (BCC). This difference accounts for contrast seen in invivo images of BCC in reflection. More recent work on breast cancer is beginning to show difference between the reflected signal from tumour and benign tissue. Using probes similar to the reflection wand, it may be possible to identify these in a surgical environment to assist surgeons in the complete excision of breast cancer.


Authors: Leonard T. Hall, Hedley J. Hansen and Derek Abbott.

Title: "Simple and effective design techniques for passive mm-wave devices."

Affiliation: Centre for Biomedical Engineering (CBME) and School of Electrical & Electronic Engineering, The University of Adelaide, SA 5005, Australia.

Abstract: We present a conformal high gain antenna array made up of a linear array of radiating microstrip line elements. This approach has been applied to the front end of a 77 GHz automotive radar. The potential of this simple concept—to be applied to antenna arrays mounted on much more complex shapes—is also discussed. Additionally, we will present a number of simple but very useful transmission line transitions between microstrip, waveguide, stripline and finline. The design process is explained and a number of examples given. The potential of this approach to reduce the implementation cost and complexity is also discussed.


Author: Hedley J. Hansen

Title: "Stand-off detection using mm-wave spectroscopy."

Affiliaton: RFT Group, EWRD, Defence Science and Technology Organisation (DSTO), Endinburgh, SA 5111, Australia.

Abstract: The sub-millimeter/mm-wave frequency band contains the fundamental rotational resonance frequencies of many molecular gases composed of carbon, nitrogen, oxygen and sulphur. The high specificity of the rotational spectra to organic molecules affords mm-wave spectroscopy having potential use in remotely sensing atmospheric pollutants and the detection of airborne chemicals is gaining importance for arms control treaty verification, intelligence collection and environmental monitoring. This presentation considers the sensitivity requirements of Radio Frequency (RF) receiver systems for measuring mm-wave absorption/emission signatures. The association between a detecting receiver’s signal level and the absorbing medium’s optical depth parameter is outlined. Optical depths in an ammonia-air mixture have been measured in a laboratory-based transmission experiment using Ka-band (20-40 GHz) emissions. The suitability of state-of-the-art RF receiving systems for stand-off gaseous signature measurements is addressed.


Authors: Kodo Kawase1,2, Yuichi Ogawa,2 and Chiko Otani1

Title: "Detection of drugs in mail using THz-waves."

Affiliation: 1: RIKEN (The institute of physical and chemical research) 2: Department of Agricultural Science, Tohoku University. Kawase Initiative Research Unit, RIKEN, 2-1 Hirosawa, Wako 3510198, Japan.

Abstract: We have studied the generation of terahertz (THz) waves by optical parametric processes based on laser light scattering from the polariton mode of nonlinear crystals. Using parametric oscillation of MgO-doped LiNbO3 crystal pumped by a nano-second Q-switched Nd:YAG laser, we have realized a widely tunable coherent THz-wave sources with a simple configuration. We have also developed a novel basic technology for THz imaging, which allows detection and identification of chemicals by introducing the component spatial pattern analysis. The spatial distributions of the chemicals were obtained from terahertz multispectral transillumination images, using absorption spectra previously measured with a widely tunable THz-wave parametric oscillator. Furthermore, we have applied this technique to the detection and identification of illicit drugs concealed in envelopes. The samples we used were methamphetamine and MDMA, two of the most widely consumed illegal drugs in Japan, and aspirin as a reference.


Authors: James O. Jensen1 and Dwight L. Woolard2

Title: "U.S. Army research in terahertz sensing science & electronic technology: current progress and future directions for effective battlefield deployment."

Affiliation: 1: U.S. Army Edgwood Chemical and Biological Center, Passive Standoff Detection Team, AMSRD-ECB-RT-DP, Bldg E5554, Aberdeen Proving Ground, MD 21010-5424, USA. 2: U.S. Army Research Laboratory Army Research Office, RTP, NC 27709, USA.

Abstract: During the last few years, new research programs have emerged within the U.S. Army and the Department of Defense (DoD) that have been focused on advancing the state-of-the-art in terahertz (THz) frequency electronic technology and on investigating novel applications of THz frequency sensing. Similarly, there has been a steadily growing interest among the international scientific and technical communities in the unique challenges associated with developing a robust electronics technology and with developing a detailed understanding of the THz frequency sensing science. The last research frontier in high-frequency electronics now lies in the terahertz (or submillimeter-wave) regime between microwaves and the infrared (i.e. 0.3 – 10 THz). While the terahertz (THz) frequency regime offers many technical advantages (e.g. wider bandwidth, improved spatial resolution, compactness), the solid-state electronics capability within the THz frequency regime remains extremely limited from a basic signal source and systems perspective.

However, important applications of THz technology are rapidly emerging that are extremely relevant to basic science and to national defence. These applications include the use of fundamental interactions of THz radiation at the molecular level for sensing and characterizing chemical and biological (CB) systems. Of course, these new developments have broad ramifications to such areas as CB defense, bio-medical and molecular science. One example would be the remote sensing of anthrax. The remaining challenges associated with developing a robust THz technology that can provide adequate power while at the same time being compact and cost effective compels new innovation in source and detector device and system electronics. This presentation will focus on the main science and technology issues that are relevant for assessing the future utility of THz sensing for national defense. Specifically, the U.S. Army has maintained a focused research effort over the last decade that has sought to extend the science base for using terahertz (THz) frequency spectroscopy as a tool for the detection, identification and characterization of biological materials and agents. During this same period, a significant amount of investment has also be dedicated to the advancement of THz-frequency electronic technology that will enhance science-based laboratory investigations and that will allow for effective field deployment capabilities. This talk will overview the current progress of this research program and elaborate on future directions of the programs that seek to establish novel integrated sensor platforms that have the potential for point and remote detection of biological warfare agents.


Authors: Roger Lewis

Title: Terahertz technology and material properties

Affiliation: Engineering Physics, University of Wollongong, Northfields Avenue, Wollongong NSW 2522, Australia.

Abstract: Terahertz radiation is a powerful probe of materials properties, because many materials have characteristic energies corresponding to the energies of terahertz photons. Take the particular example of semiconductor materials: phonon energies, cyclotron energies, and the energy levels of bound states in quantum wells, all typically lie in the terahertz region. Contrariwise, the properties of materials are crucial in the development of terahertz technology. This applies to every part of the system—from emitter, through elements for transferring and manipulating the radiation, and finally to the detector. These issues will be discussed with particular emphasis on materials suitable for optical filtering, for example, to cut out near-infrared radiation from a pump laser and to simultaneously pass terahertz. The distinction will be made between the mechanism of scattering, important when the material is placed near the source, and absorption, important when the material is placed near the detector. A number of materials conventionally used for optical filtering (teflon, polystyrene) are found to have rather high absorption coefficients for terahertz radiation.


Authors: Torsten Löffler, Karsten Siebert, Noboru Hasegawa, Tobias Hahn, Mark Thomson, Gabriel Loata and Hartmut G Roskos.

Title: "Opto-electronic techniques for remote-sensing and imaging with pulsed and cw THz radiation."

Affiliation: Phys. Inst., JWG University, Robert-Mayer-Str. 2-4, D-60054 Frankfurt (Main), Germany.

Abstract: We present the concept and performance of our all-opto-electronic cw THz imaging system. This will be illustrated by some examples of THz images obtained from archived tumor and other biomedical samples. The potential of the cw-technique will be discussed in comparison to pulsed THz imaging systems. Using a THz dark-field technique, we show that scattering and diffraction of THz radiation is a further contrast mechanism. Additionally, based on results of our pulsed-THz remote sensing set-up, we show that the identification of surfaces defects on metals (using a dark-field technique) and the characterization of interfaces in non-conducting multiple layer structures (based on time domain information) is possible. In the outlook we discuss the potential of opto-electronic cw detection for use with new high-power sources such as the novel THz-QCL’s with respect to THz radar application.


Authors: J. R. Knab, J.–Y. Chen, E. Erdemir and A. G. Markelz.

Title: Establishing THz Sensitivity of Target to Probe Binding for Pathogen Detection.

Affiliation: Physics Department, University at Buffalo, 239 Fronczak Hall, Buffalo, NY 14260, USA.

Abstract: Airborne pathogen detection methods vary with pathogen, requiring multiple platforms for complete screening. The vibrational modes associated with large scale structural motion of biomolecules lay in the THz frequency range. These vibrational modes are highly sensitive to biomolecule-biomolecule binding, and thus the monitoring of the distribution of modes could be an ideal universal method for pathogen-antibody binding detection. For example, recently authors have demonstrated a significant change in the vibrational density of states in the 5-20 cm-1 frequency range with ligand binding using inelastic neutron scattering (INS). INS is not conceivable as a pathogen monitoring method, however terahertz dielectric spectroscopy, which probes the same vibrational modes, is a viable method for in situ monitoring. We have demonstrated a strong resemblance between THz dielectric response and vibrational mode density of states and have used the method of terahertz time domain spectroscopy (TTDS) to determine the change in mode density with protein conformation, oxidation state and hydration. These measurements establish the monitoring conditions required for using TTDS for pathogen detection. In particular we find that for relative humidities (r.h.) below 60%, the dielectric response is relatively insensitive to small changes in humidity, however above 60%, the THz absorbance and index increase rapidly with small changes in r.h. as the first solvation shell is completed. We will review these results and their impact on our ligand binding measurements in xerogels.


Authors: Samuel P Mickan.

Title: "T-ray Biosensing."

Affiliation: Centre for Biomedical Engineering (CBME) and School of Electrical & Electronic Engineering, The University of Adelaide, SA 5005, Australia.

Abstract: A biosensor consists of two parts: a sensitive biological element and a physiochemical transducer/sensor. Biosensor technology was born with the oxygen electrode in 1956; today biosensing is used to detect tiny concentrations of biomolecules such as nucleic acids, hormones, antibodies and blood constituents.

Many sensitive biological elements can be used as bioreceptors, including antigens, antibodies, nucleic acids, catalysts. Similarly, many technologies have been used as transducers in biosensors, including charge sensors, temperature sensors, mass sensors, infrared spectroscopy, Raman spectroscopy, fluorescence and surface plasmon resonance.

Terahertz spectroscopy offers an alternative that will sense unique properties of the biosensor—for example, hydration, large-scale structure or hydrogen bonding. Biosensing based on the terahertz response of biomolecules has detected DNA hybridisation in a variety of forms, and biotin-avidin binding in thin films.

The importance of biosensing in defence, security, hazard control and environmental monitoring is expanding as biosensors become cheaper and more sensitive. T-ray biosensors have the potential for very high sensitivity and selectivity in certain applications.


Authors: Samuel P. Mickan.

Title: "A national user-facility for advanced T-ray imaging and spectroscopy."

Affiliation: Centre for Biomedical Engineering (CBME) and School of Electrical & Electronic Engineering, The University of Adelaide, SA 5005, Australia.

Abstract: The terahertz group at the University of Adelaide has received Federal funding to establish a T-ray User Facility in 2005, for use by researchers nationally and world-wide. Although there are many large T-ray groups around the world, the specialised nature of most T-ray systems has limited access to collaborative projects. The proposed facility will enable scientists from all backgrounds to explore the possibilities of the terahertz spectrum in their specific application areas. We propose a cluster of T-ray systems that will address: (i) gas sensing, (ii) low-noise liquid sensing, and (iii) biomaterial sensing in the nearfield. By opening terahertz sensing and imaging to a broad scientific community, new applications for T-rays will be developed and promoted, leading to new breakthroughs of strategic importance.


Authors: Robert E. Miles, Mira Naftaly, Mark Stringer, Michael Stone.

Title: "Terahertz science and technology for material identification and classification."

Affiliation: School of Electronic Engineering, University of Leeds, Leeds LS2 9JT, UK.

Abstract: This paper will discuss how terahertz (THz) frequency technology and spectroscopy can be used to identify and determine the condition of a range of materials, which have potential use in criminal activity. The requirements needed of practical systems for operational use will also be summarised.

THz frequency radiation interacts with matter in a number of ways:- in solids and liquids the (complex) dielectric constant is a measure of the propagation velocity of the radiation and any absorption that occurs in for example intramolecular bonds and phonons. Furthermore, scattering at dielectric discontinuities provides a means of probing the internal 3-D structure of a complex composite material. In gasses the relative isolation of the molecules leads to sharp resonant peaks at precisely defined frequencies. THz radiation is strongly absorbed in polar materials, the most obvious example being water. Whilst this absorption precludes the transmission of the radiation over long distances in the atmosphere or through more than a millimetre or so of liquid water, transmission over tens of metres in air is quite possible and the radiation can penetrate a few millimetres of biological tissue.

Therefore, when considering possible applications and uses at THz frequencies the considerations mentioned above must be kept in mind.

THz Spectroscopy: Materials with potential interest in security and crime fighting which have been studied include glasses, fabrics, lubricating oils and various types of paper.

(i) Glasses: Clear distinctions exist between the spectra of silica based and borosilicate glasses. The materials can therefore be identified from a single calibrated spectral line which can be obtained in just a few seconds.

(ii) Oils: THz spectra obtained for a range of lubricating oils of various viscosities and additive content reveal sufficient detail to differentiate between the different types.

(iii) Fabrics: The two-dimensional “warp and weft” structure of fabrics can be identified using polarised THz radiation. In addition the spectra can be used to identify different materials (linen, cotton, etc.)

(iv) Papers:. THz frequency characterisation has the potential of identifying paper types, their origins and, by comparing samples, to establish possible links. In addition, THz images have been used to view water-marks and therefore assist in detecting forgeries.

THz Systems:- At the present time most THz work is being carried out using techniques based on laboratory based Ti:sapph lasers delivering femtosecond pulses. In many instances, laboratory inspection is perfectly acceptable but for "scene of crime" use more portable "hand held" equipment is required. Such equipment is likely to be based on semiconductor devices but this may not exclusively be the case.


Authors: Tamath Rainsford, Sam Mickan, and Derek Abbott.

Title: "Terahertz sensing and imaging—global review of applications."

Abstract: THz wavelengths are long enough to pass through dry, non-polar objects opaque at visible wavelengths, but short enough to be manipulated by optical components to form an image. Sensing in this band potentially provides advantages in a number of areas of interest to security and defence such as screening of personnel for hidden objects and the detection of chemical and biological agents. This paper reviews recent research into THz applications by groups across Europe, the US, Australasia, and the UK. Several private companies are developing smaller, reliable cheaper devices allowing for commercialisation of these applications. While there are a number of challenges to be overcome there is little doubt that THz technologies will play a major role in the near future advancement of security, public health and defence.


Authors: A. W. Thomas and G.P. Williams.

Title: "The free electron laser at Jefferson lab: the technology and the science."

Affiliation: Thomas Jefferson National Accelerator Facility, 12000 Jefferson Ave., Newport News, VA 23606, USA.

Abstract: The free electron laser at Jefferson Lab is producing beams of infrared and THz radiation with intensities a miilion times greater than other sources. It will soon produce UV radiation of similar intensity. Coupled with its unique time structure the facility has enormous discovery potential in physics, chemistry and the biological and biomedical sciences. It also presents an enormous range of possibilities in applied science and engineering.

Authors: D.W. van der Weide, M. Choi and A. Bettermann.

Title: "Antennas and electronics for sub-THz stand-off spectroscopic imaging."

Affiliation: Department of Electrical & Computer Engineering, University of Wisconsin, 1415 Engineering Dr., Madison, WI 53711, USA.

Abstract: Broadband sensing and spectroscopic imaging using both reflection and transmission in the 1-1000 GHz regime can be carried out with pulsed terahertz (THz) circuits, such as nonlinear transmission lines (NLTLs). Yet some of the most significant limitations of any time-domain THz system—whether purely electronic or optoelectronic—arise from the lack of amplifiers, whether power or low-noise. To address this pressing need, we have been developing ultrawideband (UWB) antennas that have greater gain and better polarization characteristics than the planar antennas used in today’s THz systems. Many concepts imported from lower-frequency UWB systems are valid for the THz regime, as well, and we will describe our recent results in this area.

We take two approaches to these coherent measurements: (1) using a conventional source/detector arrangement with sampling detectors, (2) spatially combining the freely propagating beams from two matched picosecond pulse generators. The latter method employs a dual-source interferometer (DSI) modulating each harmonic of one source with a precisely-offset harmonic from the other source—both sources being driven with stable phase-locked synthesizers—the resultant beat frequency can be low enough for detection by a standard bolometer. Room-temperature detection possibilities for the DSI include antenna-coupled Schottky diodes. We have also developed a reflectometer based on serrodyne modulation of a linearized delay line, using a technique that is process-compatible with pulse generator circuits.

Finally, using the reflection configuration, we have measured absorption characteristics of a variety of targets, including Bacillus spores collected on optical micropillars. Thus, applying THz electronic systems as broadband, standoff sensors will be enabled by the benefits gained from new antennas and optical arrangements.


Authors: David Zimdars, John Federici and Ruth Woodward.

Title: "Terahertz instrumentation for security and non-destructive evaluation."

Affiliation: Picometrix, Inc. 2925 Boardwalk Dr., Ann Arbor, MI 48104, USA.

Abstract: Terahertz imaging has the potential to reveal concealed explosives; metallic and non-metallic weapons (such as ceramic, plastic or composite guns and knives); flammables; biological agents; chemical weapons and other threats hidden in packages or on personnel. THz imaging employs safe low power non-ionizing electromagnetic pulses, which produce images with high spatial resolution. In addition to density and attenuation measurements, THz pulses can be analyzed spectroscopically to reveal chemical content. Recently, highly integrated turn-key THz imaging systems have been introduced commercially. An industrially hardened THz scanning system which has been deployed to scan the space shuttle tank with small remote THz transceiver on a 30 meter fiber optic umbilical, will be described. We will describe miniature fiber optic pigtailed terahertz transmitter and receiver modules enabling this technology. We will discuss developments in the developments for short range THz imaging appropriate for security screening and/or industrial non-destructive examination (NDE). As example applications, we will demonstrate images of threat items beneath clothing (security), and the detection of voids and disbonds intentionally incorporated within the sprayed on foam insulation of a space shuttle external tank mock-up segment using time domain terahertz (a.k.a T-ray) imaging (NDE). The development of long-range interferometric THz imaging for the stand-off detection of explosives will be discussed.


Authors: Xi-Cheng Zhang

Title: Terahertz wave spectroscopy and imaging for defense applications

Affiliation: Center for Terahertz Research, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.

Abstract: Terahertz (THz) radiation offers innovative imaging and sensing technologies that can provide information not available through conventional methods such as microwave and X-ray techniques. As THz wave (T-ray) technology improves, we believe new T-ray capabilities will impact a range of interdisciplinary fields, including chemical and biological identification. This is particularly crucial for the identifying terrorist threats.

T-rays have several advantages over other sensing and imaging techniques. While microwave and X-ray imaging modalities produce density pictures, T-ray imaging also provides spectroscopic information within the THz frequency range. The unique rotational and vibrational responses of biological materials within the THz range provide information that is generally absent in optical, X-ray and NMR images. T-rays can also easily penetrate and image inside most dielectric materials, which are opaque to visible light and low contrast to X-rays, making T-rays a useful and complementary imaging source in this context.

T-rays offer the opportunity for transformational advances in defense and security. Recent work shows that T-rays have promise as a means identifying explosive compounds. Unique features in THz frequency have been obtained. Examples of such applications to identify terrorist threats include terahertz spectroscopy of biomaterial identification with fingerprint in terahertz range, and remote sensing and imaging of explosive targets.




Invited Poster Presentations: (listed in alphabetical order of presenting author)

  • Note: student posters are permitted to be on any RF topic, as well as mm-wave and THz. There will be a $2500 IEEE Prize for the best of these student posters. Follow the link to check the IEEE rules and conditions.
  • The RF posters do not appear on this list, but will be displayed at the workshop.
  • Note that all posters should be erected at 8:00am on the 16th of December. They will be up for the whole of the workshop and can be viewed throughout all coffee breaks.


Authors: Chien Aun Chan, Samuel P. Mickan, Gywn P. Williams and Derek Abbott.

Title: "Terahertz calculations for the Australian synchrotron."

Affiliation: Centre for Biomedical Engineering (CBME) and School of Electrical & Electronic Engineering, The University of Adelaide, SA 5005, Australia.

Abstract: The development of terahertz radiation (T-rays) is spurring new applications in spectroscopy and imaging. To maximize the use of T-rays in more applications, a high average terahertz power is needed. Rather than using fast diodes or laser sources, this paper will show that a synchrotron can generate high average power T-rays. This is achieved by creating an electron bunch in the synchrotron ring with high intensity in the terahertz frequency region via Thomson scattering.


Authors: Stephen V. Milton

Title: "Electron beam properties and high-power synchrotron radiation Generation and Radiation Properties

Affiliation: Argonne National Laboratory, Advanced Photon Source, 9700 S. Cass Ave., Argonne, Illinois,
60439, USA.

Abstract: An electron transversely accelerated by a magnetic field emits electromagnetic (EM) radiation whose properties are very well understood. The emission from an ensemble of electrons is also very well understood; however, it is obvious that the electron ensemble distribution affects the properties of the emitted EM radiation. Depending on its properties an electron bunch can exhibit transverse and/or longitudinal coherent EM emission. In both cases tremendous gains in the photon brightness can be obtained. We will provide a review of the EM emission from an ensemble of electrons. Particular attention will be given to coherent emission at longer wavelengths (microns to millimeters).


Authors: R. Mendis, C. Sydlo, J. Sigmund, M. Feiginov, P. Meissner, H. L. Hartnagel.

Title: "Spectral characterisation of THz antennas via photomixing."

Affiliation: University of Wollongong, Faculty of Engineering, Wollongong, NSW 2522, Australia, and Darmstadt University of Technology, Institute of High-Frequency Engineering, Merckstrasse 25, 64283 Darmstadt, Germany.

Abstract: We report on the spectral characterization of a planar photoconductive antenna using coherently generated and detected continuous THz waves. The experimental setup operates in the frequency-domain as a broadly tunable, continuous-wave (CW) THz system, where the transmitter (Tx) and receiver (Rx) antennas are integrated with low-temperature-grown (LTG) GaAs based interdigitated finger photomixers. The photomixer integrated antennas on both the Tx and Rx have identical log-periodic circular-toothed structures with an outer diameter of 1.28 mm. To the best of our knowledge, this is the first time, antennas of this type, coupled with LTG-GaAs based finger-photomixers, have been used in this CW THz pump-probe system configuration.

CW THz systems based on photomixing (or photoconductive mixing) are more attractive than their pulse counterpart in terms of frequency resolution (a few MHz compared to several GHz) and spectral brightness (~ 10,000 times), and have been gaining ground in recent years. A CW system driven by laser diodes would also be more economical and compact compared to a typical pulse system driven by a Ti:Sapphire laser. Furthermore, by providing access to single frequencies, a CW system allows real-time measurements in the frequency-domain. Coupled with a photoconductive detection scheme that provides both amplitude and phase information, the complete system operates at room temperature. These properties make it ideal for high-resolution spectroscopy, CW imaging, and other frequency-domain applications. By careful control of the optical input power, the single-frequency nature of the system provides the unique ability to minimize the photocurrent response that would otherwise play a significant role in the frequency response of a pulse THz system. This is vital when one uses this type of photoconductive system to extract spectral properties of the antenna, where the photocurrent response may act to mask the antenna response, in particular, resonance behaviour.

We examine the antenna behaviour through the frequency response of the system and show that the antenna exhibits a log-periodic behaviour at low frequencies, and a bow-tie behaviour at high frequencies, with a sharp resonance characteristic in between, well in agreement with the antenna geometry. Based on these results, we predict that an improved geometry that extends the log-periodic behaviour to higher frequencies would enable the generation of broadband THz power levels that challenge the state-of-the-art.


Authors: Gretel M. Png, Tamath Rainsford, Samuel P. Mickan, Derek Abbott.

Title: "Terahertz phase contrast imaging."

Affiliation: Centre for Biomedical Engineering (CBME) and School of Electrical & Electronic Engineering, The University of Adelaide, SA 5005, Australia.

Abstract: Terahertz imaging is presently in its exploratory stage. Although plots of time versus terahertz amplitude, and frequency versus terahertz magnitude are some of the most common ways of analyzing terahertz data, no standard rendering technique has been established. While existing methods are indispensable, improvements as to how terahertz data is rendered and analyzed should be explored so that new techniques can complement existing ones and/or provide a means of displaying new information that existing methods cannot. This paper reports on one solution to terahertz imaging: an implementation of a new form of phase contrast imaging, which is based on a well-established technique for optical microscopy. This will provide us with a further way of interpreting information from terahertz imaging systems.


Authors: Withawat Withayachumnankul, Samuel P. Mickan, Derek Abbott.

Title: "Estimating parameters of inhomogeneous materials via THz-TDS, using power series expansion."

Affiliation: Centre for Biomedical Engineering (CBME) and School of Electrical & Electronic Engineering, The University of Adelaide, SA 5005, Australia.

Abstract: Terahertz time-domain spectroscopy is useful for inspection, since terahertz radiation can pass through dry, non-metallic, and non-polar substances. When the signal penetrates a material, its signature is changed by the absorption and dispersion properties of the material. These properties can be used to classify different types of materials because they are unique. In this poster a method for estimating parameters for inhomogeneous materials is presented. Based on the least-square fitting technique, the method can derive the complex refractive index and thickness of homogeneous or inhomogeneous materials from the reference and transmitted signals.