We investigated the signature phenomenology of long-wave infrared (LWIR) reflectance of contaminated surfaces using
a quantum-cascade laser (QCL) that tunes from λ = 9.1 to 9.8 μm and a HgCdTe focal-plane-array (FPA) with custom
read-out integrated circuit (ROIC). A liquid chemical, diethyl phthalate (DEP), was applied to a variety of substrates
such as diffusely reflecting gold, concrete, asphalt, and sand. Multispectral image-cubes of the scattered radiation were
generated over 81 wavelengths in steps of 1 cm-1 at standoff distances ranging from 0.1 to 5 meters. For idealized
substrates such as diffusely reflecting gold, the experimentally measured signatures are in good agreement with
theoretical calculations. Clear signatures were also obtained for contaminated concrete, asphalt, and sand. These
measurements demonstrate the potential of this technique for detecting and classifying chemicals on native outdoor
surfaces.
This paper describes the development and initial validation of a bioaerosol optical sensor model. This model was used
to help determine design parameters and estimate performance of a new low-cost optical sensor for detecting
bioterrorism agents. In order to estimate sensor performance in detecting biowarfare simulants and rejecting
environmental interferents, use was made of a previously reported catalog of EEM (excitation/emission matrix)
fluorescence cross-section measurements and previously reported multiwavelength-excitation biosensor modeling work.
In the present study, the biosensor modeled employs a single high-power 365 nm UV LED source plus an IR laser diode
for particle size determination. The sensor has four output channels: IR size channel, UV elastic channel and two
fluorescence channels. The sensor simulation was used to select the fluorescence channel wavelengths of 400-450 and
450-600 nm. Using these selected fluorescence channels, the performance of the sensor in detecting simulants and
rejecting interferents was estimated. Preliminary measurements with the sensor are presented which compare favorably
with the simulation results.
We are investigating the utility of UV light emitting diodes (LEDs) as the excitation source for fluorescence-based biological agent detection. These LEDs may enable the development of small and low-cost biological agent detectors. We have designed, and are currently fabricating, a test bed using UV LEDs for detecting biological agent aerosols. Using an experimental apparatus, we have measured the elastic scattering and fluorescence signals from single bacterial spores illuminated by low-power 408-nm laser diode radiation.
Artificial beacons generated at the sodium layer have many advantages for adaptive optics (AO) systems in astronomy. The source can be sufficiently bright to achieve high Strehl ratios at infrared wavelengths and because the target object can often be used as the tracking source, photometric field errors can be much reduced compared to off-axis natural beacons. The problem has been to develop a laser that could be tuned to the sodium D2 line and focused into a compact spot without saturating the layer. Both CW and sum frequency lasers are well suited for this work will be used for the ChAOS AO system described elsewhere in this conference. In this paper we discuss some of the parameters that determine how well CW work, the limitations of pulsed lasers and the development of a 10 watt diode laser pumped sum frequency laser for use in astronomy.
Conference Committee Involvement (5)
Optically Based Biological and Chemical Detection for Defence V
1 September 2009 | Berlin, Germany
Optically Based Biological and Chemical Detection for Defence IV
16 September 2008 | Cardiff, Wales, United Kingdom
Optically Based Biological and Chemical Detection for Defence
18 September 2007 | Florence, Italy
Optically-Based Biological and Chemical Detection for Defence III
11 September 2006 | Stockholm, Sweden
Optically Based Biological and Chemical Sensing for Defence
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