Showing papers in "International Journal of High Speed Electronics and Systems in 2008"
TL;DR: In this article, the authors investigated the use of high data rate for 3D collision avoidance and object tracking using 3D flash ladar cameras fabricated by Advanced Scientific Concepts, Inc.
Abstract: 3-D flash ladar, herein defined as obtaining an entire frame of 3-D ladar data with one laser pulse, is an emerging technology with a number of advantages over conventional point scanner systems. Probably the most obvious advantage is the higher data rates possible and the potential for much higher data rates with increases in the associated 3-D focal planes array (FPA) format. High data rate means that topographical mapping, for example, can be obtained more rapidly decreasing the amount of flight time required. This paper investigates the clear but perhaps not-so-intuitive use of the high data rate: time dependent 3-D movies can be acquired at the repetition frequency of the associated laser. Data is taken using 3-D flash ladar cameras fabricated by Advanced Scientific Concepts, Inc. The paper concludes that there are a number of advantages and unique applications of the time dynamic 3-D flash ladar, including 3-D collision avoidance and object tracking.
59 citations
TL;DR: In this paper, a novel nanoscale-engineering methodology is presented that has potential for the first-time development of a microscope-system capable of collecting terahertz (THz) frequency spectroscopic signatures from microscopic biological (bio) structures.
Abstract: A novel nanoscale-engineering methodology is presented that has potential for the first-time development of a microscope-system capable of collecting terahertz (THz) frequency spectroscopic signatures from microscopic biological (bio) structures. This unique THz transmission microscopy approach is motivated by prior studies on bio-materials and bio-agents (e.g., DNA, RNA and bacterial spores) that have produced spectral features within the THz frequency regime (i.e., ~ 300 GHz to 1000 GHz) that appear to be representative of the internal structure and characteristics of the constituent bio-molecules. The suggested THz transmission microscopy is a fundamentally new technological approach that seeks to avoid the limitations that exist in traditional experiments (i.e., that must average over large numbers of microscopic molecules) by prescribing a viable technique whereby the THz frequency signatures may be collected from individual bio-molecules and/or microscopic biological constructs. Specifically, it is possible to envision the development of a “nanoscale imaging array” that possesses the characteristics necessary (e.g., sub-wavelength resolution) for successfully performing “THz-frequency microscopy.”
18 citations
TL;DR: In this paper, the effects of an electric field on electron kinetics and transport in quantum-dot structures with potential barriers created around dots via intentional or unintentional doping were investigated using Monte-Carlo simulations.
Abstract: Employing Monte-Carlo simulations we investigate effects of an electric field on electron kinetics and transport in quantum-dot structures with potential barriers created around dots via intentional or unintentional doping. Results of our simulations demonstrate that the photoelectron capture is substantially enhanced in strong electric fields and this process has an exponential character. Detailed analysis shows that effects of the electric field on electron capture in the structures with barriers are not sensitive to the redistribution of electrons between valleys and these effects are not related to an increase of drift velocity. Most data find adequate explanation in the model of hot-electron transport in the potential relief of quantum dots. Electron kinetics controllable by potential barriers and an electric field may provide significant improvements in the photoconductive gain, detectivity, and responsivity of photodetectors.
14 citations
TL;DR: In this paper, a terahertz (THz) quantum-cascade laser with record performance was developed, using those high-power lasers as the illumination sources and a focal-plane array camera.
Abstract: We report our development of terahertz (THz) quantum-cascade lasers with record performance. Using those high-power lasers as the illumination sources and a focal-plane array camera, we are able to perform real-time THz imaging at video rate.
12 citations
TL;DR: In this paper, the authors investigated the short-channel effect (SCE), floating-body effect, and three-dimensional coupling effect in triple-gate MOSFETs with various fin widths, gate lengths and number of fins.
Abstract: We have investigated the short-channel effect (SCE), floating-body effect, and three-dimensional coupling effect in triple-gate MOSFET with various fin widths, gate lengths and number of fins. It is found that the SCE of these devices is alleviated as the fin width shrinks and does not depend on the number of fins. The gate-induced floating-body effect (GIFBE) is visible even in fully depleted (FD) triple-gate transistors when the film-buried oxide (BOX) interface is swept from depletion to accumulation by the back-gate bias. The 3-D coupling effect in vertical, lateral, and longitudinal directions was investigated for different channel geometries. The biasing condition which enables the simultaneous activation of all channels and gives rise to volume inversion is discussed.
11 citations
TL;DR: In this article, a semiconductor scintillation-type gamma radiation detector is discussed in which the gamma-ray absorbing semiconductor body is impregnated with multiple small direct-gap semiconductor inclusions of bandgap slightly narrower than that of the body.
Abstract: A semiconductor scintillation-type gamma radiation detector is discussed in which the gamma-ray absorbing semiconductor body is impregnated with multiple small direct-gap semiconductor inclusions of bandgap slightly narrower than that of the body. If the typical distance between them is smaller than the diffusion length of carriers in the body material, the photo-generated electrons and holes will recombine inside the impregnations and produce scintillating radiation to which the wide-gap body is essentially transparent. In this way it is possible to implement a semiconductor scintillator of linear dimensions exceeding 10 cm.
11 citations
TL;DR: In this article, a visible, hyperspectral imager using chromotomography CT was built, with the goal of extending the technology to spatially extended sources with quickly varying (> 10 Hz) features, such as bomb detonations and muzzle flashes.
Abstract: A visible, hyperspectral imager using chromotomography CT) has been built, with the goal of extending the technology to spatially extended sources with quickly varying (> 10 Hz) features, such as bomb detonations and muzzle flashes. Even with a low dispersion, ~0.7 mrad/nm, direct vision prism with undeviated wavelength near λ = 548 nm, spectral resolution of better than Δ λ < 10 nm across the λ = 400 – 600 nm band is demonstrated with spatial resolution of better than 0.5 mm. The primary objective of this paper is to show empirically that the spatial and spectral resolution of data obtained by a simple CT instrument is unchanged in projection space and reconstructed object space.
11 citations
TL;DR: In this article, a comparative analysis of different wavelength ranges for the spectroscopic detection of acetone vapor is presented, taking into account the absorption strength, available technology, and possible interferences.
Abstract: This paper presents comparative analysis of different wavelength ranges for the spectroscopic detection of acetone vapor. We collected and analyzed original absorption line spectra arising from electronic transitions in the ultraviolet, near-infrared vibrational overtones, mid-infrared fundamentals, THz torsional modes, and mm-wave rotational transitions. Peak absorption cross sections of prominent spectral features are determined. The relative merit of each spectral range for sensing is considered, taking into account the absorption strength, available technology, and possible interferences.
11 citations
TL;DR: In this paper, an overview of III-V MOSFET technological challenges in comparison to well-established heterostructure-based FET technologies is presented with an emphasis on required properties and possible solutions.
Abstract: An overview of III-V MOSFET technological challenges in comparison to well-established heterostructure-based FET technologies is presented with an emphasis on required properties and possible solutions. Possible approaches to achieve thermodynamically stable high-k gate stack with low interface trap density are reviewed, followed with our results on amorphous Si interface passivation layer (IPL) in-situ deposited on top of GaAs or strained InGaAs MOSFET channels grown by molecular beam epitaxy. Main issues of Si IPL, namely increased equivalent oxide thickness due to IPL oxidation and Si diffusion into the semiconductor channel, are addressed using an in-situ deposited HfO2 with ultrathin (down to 0.25 nm) Si IPL and controlling its bonding state at the interface. Enhancement mode inversion-type MOSFET with HfO2 high-k oxide is demonstrated. The device employs amorphous Si interface passivation layer, sputter-deposited high-k oxide and metal TaN gate and modulation p-doped GaAs/AlGaAs heterostructure with inversion n-channel formed at the interface with the oxide. The MOSFET with equivalent oxide thickness of 3.7 nm and long 100 μm channel have maximum DC transonductance of 0.9 mS/mm, Ion/Ioff = 2×104 (at low Ioff of 30 nA) and effective channel mobility exceeding 1000 cm2/V-s at sheet electron density <2×1012 cm-2.
10 citations
TL;DR: The experimental and computational study of bacterial thioredoxin, an E. coli protein, at THz frequencies is presented in this article, where the absorption spectrum of the entire protein in water was studied numerically in the terahertz range (0.1 − 2 THz).
Abstract: The experimental and computational study of bacterial thioredoxin, an E. coli protein, at THz frequencies is presented. The absorption spectrum of the entire protein in water was studied numerically in the terahertz range (0.1 – 2 THz). In our work, the initial X-ray molecular structure of thioredoxin was optimized using the molecular dynamical (MD) simulations at room temperature and atmospheric pressure. The effect of a liquid content of a bacterial cell was taken into account explicitly via the simulation of water molecules using the TIP3P water model. Using atomic trajectories from the room-temperature MD simulations, thioredoxin's THz vibrational spectrum and the absorption coefficient were calculated in a quasi harmonic approximation. For our terahertz transmission measurements, we used solutions of thioredoxin in distilled water obtained from Sigma. The experimental and simulated signatures are correlated and dominant peaks are close in frequencies. The results of this study demonstrate that terahertz spectroscopy is a promising tool in generating spectral data for cellular components of bio agents such as bacterial cells and spores.
9 citations
TL;DR: In this article, the authors presented the phenomenology of detonation fireballs and explored the utility of physics-based features for explosive classification by modeling the spectra as a single-temperature Planckian.
Abstract: Conventional munitions emit intense radiation upon detonation which spans much of the electromagnetic spectrum. The phenomenology of time-resolved visible, near- and mid-IR spectra from these fast transient events is poorly understood. The observed spectrum is driven by many factors including the type, size and age of the chemical explosive, method of detonation, interaction with the environment, and the casing used to enclose the explosive. Midwave infrared emissions (1800–6000 cm-1, 1.67–5.56 μm) from a variety of conventional military munitions were collected with a Fourier transform spectrometer (16 cm-1, 21 Hz) to assess the possibility of event classification via remotely sensed spectra. Conventional munitions fireballs appear to be graybodies in the midwave. Modeling the spectra as a single-temperature Planckian (appropriately modified by atmospheric transmittance) provided key features for classification and substantially reduced the dimensionality of the data. The temperature cools from ~1800 K to ambient conditions in 3–5 s, often following an exponential decay with a rate near 1 s-1 second. A systematic, large residual spanning 2050–2250 cm-1 was consistently observed shortly after detonation and may be attributable to hot CO2 emission at the periphery of the fireball. For two different explosive types detonated under similar conditions, features based on the temperature, area and fit residuals could be used to distinguish between them. This paper will present the phenomenology of detonation fireballs and explore the utility of physics-based features for explosive classification.
TL;DR: The Advanced Responsive Tactically-Effective Military Imaging Spectrometer (ARTEMIS) is under development for tactical military applications and is the primary payload for the TacSat-3 satellite.
Abstract: The Advanced Responsive Tactically-Effective Military Imaging Spectrometer (ARTEMIS) is under development for tactical military applications and is the primary payload for the TacSat-3 satellite. The optical design for the telescope, imaging spectrometer, and high resolution imager is described.
TL;DR: In this article, a new analytical model of a Heterostructure Field Effect Transistors (HFETs) that accounts for electron trapping in the gate-drain spacing of the device and for related non-ideal device behavior was described.
Abstract: We describe a new analytical model of a Heterostructure Field Effect Transistors (HFETs) that accounts for electron trapping in the gate-drain spacing of the device and for related non-ideal device behavior. Under conditions of a very strong trapping, the electron velocity saturates outside the gate, in the trapping region, and the negative trapped charge leads to relatively large differential output conductance at the drain voltages exceeding the knee voltage. Also under the conditions of severe trapping, the negative trapped charge leads to the positive offset of the output current-voltage (I-V) characteristic. The model describes quite well numerous experimental data for passivated and unpassivated AlGaN/GaN HFETs with and without field plates (FP) under different bias conditions.
TL;DR: In this paper, a method is introduced to characterize the properties of dense dust clouds with passive IR spectral measurements, based on the solution of the appropriate radiative transfer equations, and actual field measurements of silicone-oil aerosol clouds with an IR spectro-radiometer are analyzed and compared with the theoretical model predictions.
Abstract: Heavy loads of aerosols in the air have considerable health effects in individuals who suffer from chronic breathing difficulties. This problem is more acute in the Middle-East, where dust storms in winter and spring transverse from the neighboring deserts into dense populated areas. Discrimination between the dust types and association with their source can assist in assessment of the expected health effects. A method is introduced to characterize the properties of dense dust clouds with passive IR spectral measurements. First, we introduce a model based on the solution of the appropriate radiative transfer equations. Model predictions are presented and discussed. Actual field measurements of silicone-oil aerosol clouds with an IR spectro-radiometer are analyzed and compared with the theoretical model predictions. Silicone-oil aerosol clouds have been used instead of dust in our research, since they are composed of one compound in the form of spherical droplets and their release is easily controlled and repetitive. Both the theoretical model and the experimental results clearly show that discrimination between different dust types using IR spectral measurements is feasible. The dependence of this technique on measurement conditions, its limitations, and the future work needed for its practical application of this technique is discussed.
TL;DR: A simulation study using molecular dynamics and the density-functional-theory/non-equilibrium-Green's function approach has been carried out to investigate the potential of carbon nanotubes (CNT) as molecular-scale biosensors as discussed by the authors.
Abstract: A simulation study using molecular dynamics and the density-functional-theory/non-equilibrium-Green's-function approach has been carried out to investigate the potential of carbon nanotubes (CNT) as molecular-scale biosensors. Single molecules of each of two amino acids (isoleucine and asparagine) were used as the target molecules in two separate simulations. The results show a significant suppression of the local density of states (LDOS) in both cases, with a distinct response for each molecule. This is promising for the prospect of CNT-based single-molecule sensors that might depend on the LDOS, e.g., devices that respond to changes in either conductance or electroluminescence.
TL;DR: In this article, the authors report advances in signal processing of multicomponent Raman Spectra of particulate matter and evaluate laboratory and ambient samples collected in field experiments in Canada (during the Pacific 2001 Experiment, Vancouver, BC and at ALERT station, Nunavut, 2002).
Abstract: We report advances in the signal processing of Multicomponent Raman Spectra of particulate matter. We evaluate laboratory and ambient samples collected in field experiments in Canada (during the Pacific 2001 Experiment, Vancouver, BC and at ALERT station, Nunavut, 2002). We discuss methodologies for signal processing the Raman spectra: de-noising and de-peaking, baseline reduction, and identification of chemical fingerprints. The ambient samples were collected near the surface in different environmental conditions during field experiments. In this article we compare and assess the methodologies performances and differences.
TL;DR: In this article, the process flow for the fabrication of un-cooled IR detectors employing surface micro-machining techniques over silicon substrates is presented, and two device configurations have been designed and fabricated, labeled planar and sandwich.
Abstract: In this work we present the process flow for the fabrication of un-cooled IR detectors employing surface micro-machining techniques over silicon substrates. These detectors are based on thin films deposited by plasma at low temperatures. The thermo sensing film used is an intrinsic a-SixGe1-x:H film, which has demonstrated a very high temperature coefficient of resistance (TCR), and a moderated resistivity, these properties are better than those of the a-Si:H intrinsic film, which is commonly used in commercial IR devices. Two device configurations have been designed and fabricated, labeled planar and sandwich. The former is the configuration commonly used in commercial micro-bolometers, while the latter is proposed in order to reduce the high cell resistance observed in this kind of devices, without the necessity of doping the intrinsic film, which results in a decrement of the TCR and therefore in responsivity. Finally some performance characteristics of the devices studied are discussed in comparison with data reported in literature.
TL;DR: In this article, a new pyramid-based block design for the BOS method is also introduced as opposed to the cube based block designed by Theiler et al.'s BOS.
Abstract: Pixel Purity Index (PPI) has been widely used for endmember extraction. Recently, an approach using blocks of skewers was proposed by Theiler et al., called blocks of skewers (BOS) method, to improve computation of the PPI. It utilizes a block of skewers to reduce number of calculations of dot products operated by the PPI on each skewers with all data sample vectors. Unfortunately, the BOS method also suffers from the same drawbacks that the PPI does in terms of several parameters which are needed to be determined a priori. Besides, it also has an additional parameter, block size, B needed to be determined where no guideline is provided of how to select this parameter. In this paper, the BOS method is also investigated. Most importantly, a new pyramid-based block design for the BOS method is also introduced as opposed to the cube-based block designed used by Theiler et al.'s BOS. One major advantage of our proposed pyramid-based BOS over Theiler et al.'s cube-design BOS is the hardware design for Field Programmable Gate Arrays (FPGAs) implementation.
TL;DR: In this article, a single crystal growth of KPb2Br5 by vertical Bridgman technique using in-house processed zone refined PbBr2 and KBr with rare-earth terbium doping has been studied.
Abstract: The single crystal growth of KPb2Br5 by vertical Bridgman technique using in-house processed zone refined PbBr2 and KBr with rare-earth terbium doping has been studied. The grown moisture resistant crystals (1.5 cm diameter and 10 cm length) have shown high promise for low phonon energy room temperature solid-state laser applications in the longer side of mid-IR (4-15 µm) due to their high storage lifetimes, wide tunability, and excellent optical quality. The processed crystals are highly transparent (T= ≥80%) in the 0.4-25 µm spectral region. Repeated melting-freezing cycles during differential scanning calorimetry (DSC) experiments did not reveal any appreciable variation in the melting point or phase transitions, which is indicative of their excellent thermal stability. The emission spectra pumped with a 2 µm source show broadband emissions with peak wavelength of 3 µm (7F4→ 7F6), 5µm (7F5→ 7F6) and 7.9µm (7F4→ 7F5). The KPb2Br5:Tb laser crystals will be highly useful for standoff detection of incoming chemical and biological threats using unique infrared absorption signatures.
TL;DR: In this article, the authors investigated the spectrometric LIDAR-based standoff bioaerosol detection technique to address the threat of bio-aerosols in the environment.
Abstract: Threats associated with bioaerosol weapons have been around for several decades. However, with the recent political developments that changed the image and dynamics of the international order and security, the visibility and importance of these bioaerosol threats have considerably increased. Over the last few years, Defence Research and Development Canada has investigated the spectrometric LIDAR-based standoff bioaerosol detection technique to address this menace. This technique has the advantages of rapidly monitoring the atmosphere over wide areas without physical intrusions and reporting an approaching threat before it reaches sensitive sites. However, it has the disadvantages of providing a quality of information that degrades as a function of range and bioaerosol concentration. In order to determine the importance of these disadvantages, Canada initiated in 1999 the SINBAHD (Standoff Integrated Bioaerosol Active Hyperspectral Detection) project investigating the standoff detection and characterizatio...
TL;DR: In this paper, surface-enhanced Raman spectroscopy (SERS) was used to detect dipicolinic acid (DPA) as a chemical signature of bacilli spores.
Abstract: Since the distribution of anthrax causing spores through the U.S. Postal System in the autumn of 2001, bioterrorism has become an ever present threat. During and following an attack it is also important to detect spores on surfaces, to assess the extent of an attack, to quantify risk of infection by contact, as well as to evaluate post-attack clean-up. To perform useful measurements, analyzers and/or methods must be capable of detecting as few as 10 spores/cm2, in under 5-minutes, with little or no sample preparation or false-positive responses, using a portable device. In an effort to develop such a device, we have been investigating the ability of surface-enhanced Raman spectroscopy (SERS) to detect dipicolinic acid (DPA) as a chemical signature of bacilli spores. In general, SERS is capable of detecting mg/L concentrations and lower, and providing unequivocal identification of chemicals based on each one's unique spectrum. However, rapid analysis requires extracting the DPA from the spores for SERS detection. Here we describe the use of a room temperature digesting agent in combination with SERS to detect 220 spores on a surface, the entire procedure which was performed in 2.5 minutes.
TL;DR: In this article, a new broadband Chirped-Pulse Fourier Transform Microwave (CP-FTMW) spectrometer was developed for the early detection of airborne chemical warfare agents (CWA).
Abstract: We have developed a new broadband Chirped-Pulse Fourier Transform Microwave (CP-FTMW) spectrometer that allows the microwave spectrum in the 7.5-18.5 GHz range to be measured in a single data event. This technique produces a pure rotational spectrum that can be used for unambiguous identification of any species having a permanent electric dipole moment. CP-FTMW is a gas phase technique that is ideally suited for the detection of airborne chemical warfare agents (CWA) which must be detected in trace amounts (<10 ppm in air). The high resolution of the technique allows the identification of complex mixtures without the need for a preliminary separation step, such as gas chromatography, which significantly reduces analysis time. The technique is “blind” to major atmospheric components (N2, O2, CO2, H2O) as they either do not posses a permanent dipole moment or do not absorb in the range of the spectrometer, thereby eliminating large background signals. In this paper we will present preliminary results that are focused on early detection of airborne CWA, including acquisition time, sensitivity limits, and sample handling requirements for several of these species.
TL;DR: In this article, the spectral properties of VX [O-ethyl S-(2-diisopropylaminoethyl) methylphosphonothioate] in the vapor and liquid phases were analyzed.
Abstract: Two primary goals of infrared spectroscopic detection are chemical identification and quantification. In order to accomplish these goals, a comprehensive and quantitative spectral library suitable for digital manipulation is required. To a large degree, the contents of such a library depend on the application. Since the primary application of the PNNL/DOE spectral library is for environmental monitoring, we have focused our efforts on hazardous pollutants, as well as a large variety of natural and anthropogenic chemicals. As a spin-off project and in collaboration with Dugway Proving Ground, we also had the opportunity to analyze a limited set of chemical warfare agents (CWAs). An example of such data appears below. Infrared optical properties of VX [O-ethyl S-(2-diisopropylaminoethyl) methylphosphonothioate] in the vapor and liquid phases. Refractive index data (top traces) are critical for modeling aerosol and reflection phenomena.
TL;DR: In this paper, the authors developed a small instrument based upon a Fabry-Perot interferometer that is highly sensitive to atmospheric CO2 and tested this instrument in a ground-based configuration and from aircraft platforms simulating operation from a satellite.
Abstract: To address the problem of sources and sinks of atmospheric CO2, measurements are needed on a global scale. Satellite instruments show promise, but typically measure the total column. Since sources and sinks at the surface represent a small perturbation to the total column, a precision of better than 1% is required. No species has ever been measured from space at this level. Over the last three years, we have developed a small instrument based upon a Fabry-Perot interferometer that is highly sensitive to atmospheric CO2. We have tested this instrument in a ground based configuration and from aircraft platforms simulating operation from a satellite. The instrument is characterized by high signal to noise ratio, fast response and great specificity. We have performed simulations and instrument designs for systems to detect, H2O, CO, 13CO2, CH4, CH2O, NH3, SO2, N2O, NO2, and O3. The high resolution and throughput, and small size of this instrument make it adaptable to many other atmospheric species. We present results and discuss ways this instrument can be used for ground, aircraft or space based surveillance and the detection of pollutants, toxics and industrial effluents in a variety of scenarios including battlefields, industrial monitoring, or pollution transport.
TL;DR: The TES technique presented in this paper is based on iteration on temperature principle, where a total square error criterion is used to estimate the temperature and a mathematical behavior model is provided.
Abstract: The construction of very good hyperspectral sensors operating in the thermal infrared bands from 8 to 12 microns arouses much interest for the development of data exploitation tools. Temperature emissivity separation (TES) algorithms are very important components of a future toolbox, because they make it possible to extract these two fundamental targets’ parameters. The emissivity relies on the nature of the target's surface materials, while the temperature gives information related to their use and relationship with the environment. The TES technique presented in this paper is based on iteration on temperature principle, where a total square error criterion is used to estimate the temperature. The complete procedure is described in the paper. Its sensitivity to noise is studied and a mathematical behavior model is provided. The model is validated through a Monte-Carlo simulation of the technique's operation.
TL;DR: In this paper, a database of terahertz (THz) time-domain spectroscopy (TDS) absorption spectra from bulk explosives was assembled to demonstrate selectivity of THz TDS from the clutter of background spectra coming from the substrate such as soil or sand.
Abstract: In the last few years, a number of researchers including our collaboration have assembled databases of terahertz (THz) time-domain spectroscopy (TDS) absorption spectra from bulk explosives. While this was a necessary and important step in demonstrating the feasibility of THz TDS for explosives detection, the goal of our research is to demonstrate selectivity of THz spectra from the clutter of background spectra coming from the substrate such as soil or sand. We have investigated THz TDS reflection spectra from sand with different grain sizes as well as from metallic powders in order to distinguish between the signals reflected from the rough surfaces compared to distributed reflections at finite depths in the granular material. With marker materials such as tartaric acid, which have absorption features in the 1-2 THz range, we have investigated the reflection spectra of granular substrates with marker chemicals, and compared this to reflection and transmission spectra of solid materials prepared in polyethylene sample pellets. In principle, the same experiments can then be performed using TNT, RDX, HMX and PETN, which all have characteristic features in the 0.5-8 THz frequency range. Absolute molecular absorption coefficients can be measured as well, and we include here preliminary values for RDX. A full analysis will be reported elsewhere.
TL;DR: In this paper, it is demonstrated that many explosives exhibit a signature (fingerprint) in the long-wave infrared (LWIR) region (i.e., 8 − 14 μm).
Abstract: The objective of this paper is to show that explosives may potentially be detected by passive standoff FTIR radiometry. It is demonstrated that many explosives exhibit a signature (fingerprint) in the longwave infrared (LWIR) region (i.e., 8 – 14 μm). Simulations using the radiative transfer model, MODTRAN4, clearly suggest that such materials can be identified when a thermal contrast exists between the material and its environment. The explosives considered in this study include octogen (HMX), trinitrotoluene (TNT), cyclonite (RDX), and the plastic explosives, C-4 and Detasheet-C. In addition, passive FTIR measurements of HMX have been performed in the field at standoff distances up to 60 m. The development of a passive standoff detection capability based on FTIR radiometry may be a potentially useful addition to the arsenal of measurement techniques that currently exist for the detection and identification of explosive threats.
TL;DR: In this paper, the passive standoff long wave infrared technology developed for atmospheric remote sensing was used to detect and identify chemical pollutants in the atmosphere, and the measurement approach is based on the differential passive standoff detection method that has been developed by DRDC Valcartier.
Abstract: In this paper, the passive standoff long wave infrared technology developed for atmospheric remote sensing was used to detect and identify chemical pollutants in the atmosphere. The measurement approach is based on the differential passive standoff detection method that has been developed by DRDC Valcartier during the past few years. The measurements were performed on real chemical warfare agents and toxic chemical vapors. The results clearly demonstrate the capability of the differential radiometry approach for the detection, identification and quantification of toxic chemical vapor clouds in an open-air environment.
TL;DR: In this article, an approach for the passive standoff detection of surface contaminants by differential polarization FTIR spectrometry is proposed, and the surface radiance modeling associated with the method is given.
Abstract: An approach for the passive standoff detection of surface contaminants by differential polarization FTIR spectrometry is proposed. The surface radiance modeling associated with the method is given. Unpolarized and polarized sensing measurements obtained with the CATSI sensor for the standoff detection of liquid agent VX deposited on high-reflectivity surfaces are presented. The analysis of results indicates that the differential polarization approach is well suited to mitigate sky radiance drifts, which favours unambiguous surface contaminant detections. An experimental and modeling study initiated to address the spectral polarization phenomenology is outlined. The design of an optimized FTIR sensor for differential polarization spectrometry measurements is discussed.
TL;DR: In this paper, the detection of THz radiation by a high electron mobility (HEMT) GaAs/GaAlAs transistor was investigated at 4 K as a function of the magnetic field B. The detection signal was found to be periodic in B-1, i.e., it showed Shubnikov - de Haas oscillations.
Abstract: Detection of THz radiation by a high electron mobility (HEMT) GaAs/GaAlAs transistor was investigated at 4 K as a function of the magnetic field B. The detection signal (a source - drain photovoltage appearing as a response to THz radiation) was found to be periodic in B-1, i.e., it showed Shubnikov - de Haas oscillations. A Fourier transform of the signal showed a large amplitude component independent of the gate voltage, and a small amplitude component dependent on it. This shows that a HEMT response to the radiation cannot be described either by a plasma instability in gated ("shallow water") or in ungated ("deep water") parts of the channel, but rather by a response of the channel as a whole. This is in a good correspondence with recent experimental evidence of antenna effects in detection of radiation by HEMTs and advanced theoretical models of instability of coupled gated - ungated plasma in HEMTs.