Laser based detection of gaseous, liquid and solid residues and trace amounts has been developed ever
since lasers were invented. However, the lack of availability of reasonably high power tunable lasers in
the spectral regions where the relevant targets can be interrogated as well as appropriate techniques for
high sensitivity, high selectivity detection has hampered the practical exploitation of techniques for the
detection of targets important for homeland security and defense applications. Furthermore, emphasis
has been on selectivity without particular attention being paid to the impact of interfering species on the
quality of detection. Having high sensitivity is necessary but not a sufficient condition. High sensitivity
assures a high probability of detection of the target species. However, it is only recently that the sensor
community has come to recognize that any measure of probability of detection must be associated with a
probability of false alarm, if it is to have any value as a measure of performance. This is especially true
when one attempts to compare performance characteristics of different sensors based on different
physical principles. In this paper, I will provide a methodology for characterizing the performance of
sensors utilizing optical absorption measurement techniques. However, the underlying principles are
equally application to all other sensors. While most of the current progress in high sensitivity, high
selectivity detection of CWAs, TICs and explosives involve identifying and quantifying the target species
in-situ, there is an urgent need for standoff detection of explosives from safe distances. I will describe our
results on CO2 and quantum cascade laser (QCL) based photoacoustic sensors for the detection of
CWAs, TICs and explosives as well the very new results on stand-off detection of explosives at distances
up to 150 meters. The latter results are critically important for assuring safety of military personnel in
battlefield environment, especially from improvised explosive devices (IEDs), and of civilian personnel
from terrorist attacks in metropolitan areas.
Fielded surface detection systems rely on contact with either the liquid contamination itself or the associated chemical
vapor above the contaminated surface and do not provide a standoff or remote detection capability. Conversely, standoff
chemical vapor sensing techniques have not shown efficacy in detecting those contaminants as liquids or solids on
surfaces. There are a number of optical or spectroscopic techniques that could be applied to this problem of standoff
chemical detection on surfaces. The three techniques that have received the most interest and development are laser
induced breakdown spectroscopy (LIBS), fluorescence, and Raman spectroscopy. Details will be presented on the
development of these techniques and their applicability to detecting CBRNE contamination on surfaces.
This paper reports on a low-cost, borosilicate glass-based spectroscopic sensor for the detection of water contaminants.
10 μL water samples are inserted into a sandblasted sample reservoir in a borosilicate glass substrate and are partially
evaporated with a 200 nm thin-film Cr microheater/cathode patterned to the bottom of the reservoir. The relative
contaminant concentration within the partially evaporated sample is greater, providing a means of measuring lower
concentrations of impurities. An on-chip plasma discharge is stuck to the sample, sputtering the water contaminants into
the discharge, doping its spectral emissions. Cu and Fe impurities are detected at 10 ppm in a 2.5% HNO3 solution and
Ca and Mg contaminants are detected at 100 ppm. The on-chip microheater yields temperature changes as high as 96 °C
when supplied with 100 mA. Multiple single-use sensors can be fabricated inexpensively on the borosilicate glass
substrate using simple, standard photolithography techniques.
Liquid explosives have recently been used in terrorism. Inspection of bottles has become very important, because these
liquid explosives and their raw materials can be easily carried in bottles. Hydrogen peroxide is a typical raw material of
liquid explosives. It was difficult to evaluate the concentration of hydrogen peroxide a bottled drink, because of the
similarity of its optical properties to those of water. Using the near-infrared spectrum and multivariate statistical
analysis, concentrations of a percent order of hydrogen peroxide can be evaluated from outside of the bottle instantly.
Hydrogen peroxide has been detected not only in clear PET or glass bottles but also in colored glass bottles. Hydrogen
peroxide mixed with soft drink such as coke or orange juice with pulp was also easily detected by this method. This
technique can be applied to the inspection of bottles at airport security and so on.
We present experimental results on a Quantum cascade laser (QC laser) embedded in an external cavity. These results were obtained with a broadly tunable laser exceeding 80 cm-1 covering a characteristic absorption band of trinitrotoluene
(TNT). By combining the laser source with a high performance IR imager a stand-off detection setup based on multi-
spectral MIR backscattering spectroscopy has been realized. With this technique TNT surface-contaminations of as low
as 10 μg/cm2 could be detected on surfaces such as an aluminum-sheet and standard car paint. The contrast of the
detection technique depends on the reflectance of the surface. A surface leading to mirror-like reflectance of the IR laser radiation leads to absorbance-like signatures of the TNT contamination, while surfaces showing high absorbance of the laser light may induce a contrast-reversal in the resulting image of the TNT coverage. This effect can be explained by a theoretical model for thin film coated substrates taking into account differences in the reflectance. Limitations and
further work needed to explore the full potential of the IR backscattering technique are also discussed.
The mobile demonstrator for biological aerosol standoff detection has been designed and built to test and develop
reliable optical methods for the identification of biological aerosols in a 10 km range. Disciplines such as agriculture,
defense and security are increasingly concerned with distinguishing certain classes of biological particles from remote
distances. The instrument combines backscatter channels for 3 laser wavelengths, 2 nitrogen Raman channels,
depolarization and fluorescence channels with 2 ultraviolet excitation wavelengths. Aerosol size distribution, particle
shape and refractive index as well as fluorescence excitability by different laser wavelengths and spectral fluorescence
information are the distinguishing variables for the identification of unknown biological aerosols.
Defence R&D Canada (DRDC) has developed, by the end of the 90s, a standoff bioaerosol sensor prototype based on
intensified range-gated spectrometric detection of Laser Induced Fluorescence (LIF) called SINBAHD. This LIDAR
system was used to characterize spectrally the LIF of bioaerosol agent simulants and obscurants during 57 cross-wind
open-air releases at Suffield, CAN in July 2007. An autoclave and gamma-irradiation killing procedures were performed
on Bacillus subtilis var globigii (BG) samples before they were aerosolized, disseminated and spectrally characterized.
Slight discrepancies were observed in the spectral characteristics of killed versus live samples but none between the two
killing methodologies. Significant signature variabilities were observed from the different batches of Erwinia Herbicolas
(EH). The generated cloud was simultaneously characterized in Agent Containing Particle per Liter of Air (ACPLA) by
slit sampler units and in particle per litter of air (ppl) by an Aerodynamic Particle Sizer (APS). Correlation assessment
between the stand-off sensor SINBAHD and the two referee point sensors was done, allowing an estimation of
SINBAHD's sensitivity in ACPLA and in ppl. For a 20-m thick cloud at a range of 990 m, a detection limit of a few tens
of ACPLA and a few ACPLA were obtained for BG and EH respectively. The extracted correlation between ACPLA
and ppl data for releases performed with an agricultural sprayer showed a high degree of variability: 2 to 29% and 1 to
6% of ACPLA/ppl ratio for BG and EH, respectively.
An ultraviolet (UV) laser induced fluorescence (LIF) light detection and ranging (LIDAR) system has been constructed
and commissioned by Dstl and demonstrated to be an effective technique for discriminating between some common
fluorescent potentially interfering aerosols and biological warfare agent (BWA) simulants at a distance remote from the
release. The Mk 3 UV-LIF LIDAR employs the fundamental wavelength (1064 nm) of a Nd:YAG laser to spatially map
aerosol clouds, and the fourth harmonic (266 nm) to excite fluorescence. The fluorescence emission is spectrally
resolved into ten detection channels between 300-500 nm, permitting classification by a discrimination algorithm. The
UV-LIF LIDAR was trialled in 2007 in the Joint Ambient Breeze Tunnel (JABT) and on the open range, at the US Army
Dugway Proving Ground (DPG), Utah. In the JABT, calibration instruments were used to characterise the BWA
simulant and interferent aerosol releases, permitting calculation of the system's limits of detection (LoD) and
III-Nitride based deep ultraviolet (DUV) light emitting diodes (LEDs) rapidly penetrate into sensing market owing to
several advantages over traditional UV sources (i.e. mercury, xenon and deuterium lamps). Small size, a wide choice of
peak emission wavelengths, lower power consumption and reduced cost offer flexibility to system integrators. Short
emission wavelength offer advantages for gas detection and optical sensing systems based on UV induced fluorescence.
Large modulation bandwidth for these devices makes them attractive for frequency-domain spectroscopy. We will
review present status of DUV LED technology and discuss recent advances in short wavelength emitters and high power
After attacks with anthrax pathogens have been committed since 2001 all over the world the fast detection and
determination of biological samples has attracted interest. A very promising method for a rapid test is Laser Induced
Breakdown Spectroscopy (LIBS). LIBS is an optical method which uses time-resolved or time-integrated spectral
analysis of optical plasma emission after pulsed laser excitation. Even though LIBS is well established for the
determination of metals and other inorganic materials the analysis of microbiological organisms is difficult due to their
very similar stoichiometric composition. To analyze similar LIBS-spectra computer assisted chemometrics is a very
In this paper we report on first results of developing a compact and fully automated rapid test for the detection of
hazardous microbiological material. Experiments have been carried out with two setups: A bulky one which is composed
of standard laboratory components and a compact one consisting of miniaturized industrial components. Both setups
work at an excitation wavelength of λ=1064nm (Nd:YAG). Data analysis is done by Principal Component Analysis
(PCA) with an adjacent neural network for fully automated sample identification.
Bio-aerosol terrorist attacks have been carried out against civilians in the United States and
elsewhere. Unfortunately, recurrence appears inevitable. A fast, reliable, and inexpensive bioaerosol
threat detection trigger can be an important tool for detect-to-protect and detect-to-treat
countermeasure scenarios. Bio-aerosol threat detection triggers employing light, historically laser
light but recently LED light, for induced native- or
auto-fluorescence (LIF) have been developed for
well over a decade without a generally accepted solution being found. This paper presents a brief
history of LIF triggers and reviews many vendor efforts, past and current. Various technical
approaches and design considerations are discussed. Triggers from ICx technology, currently
available or in development, are also discussed.
We have performed a field trial to evaluate technologies for stand-off detection of biological aerosols, both in daytime
and at night. Several lidar (light detection and ranging) systems were tested in parallel. We present the results from three
different lidar systems; one system for detection and localization of aerosol clouds using elastic backscattering at
1.57 μm, and two systems for detection and classification of aerosol using spectral detection of ultraviolet laser-induced
fluorescence (UV LIF) excited at 355 nm. The UV lidar systems were utilizing different technologies for the spectral
detection, a photomultiplier tube (PMT) array and an intensified charge-coupled device (ICCD), respectively. During the
first week of the field trial, the lidar systems were measuring towards a semi-closed chamber at a distance of 230 m. The
chamber was built from two docked standard 20-feet containers with air curtains in the short sides to contain the aerosol
inside the chamber. Aerosol was generated inside the semi-closed chamber and monitored by reference equipments, e.g.
slit sampler and particle counters. Signatures from several biological warfare agent simulants and interferents were
measured at different aerosol concentrations. During the second week the aerosol was released in the air and the
reference equipments were located in the centre of the test site. The lidar systems were measuring towards the test site
centre at distances of either 230 m or approximately 1 km. In this paper we are presenting results and some preliminary
signal processing for discrimination between different types of simulants and interference aerosols.