Imaging standoff detection of explosives using widely tunable midinfrared quantum cascade lasers

Fuchs, F.; Hugger, S.; Kinzer, M.; Aidam, R.; Bronner, W.; Lösch, R.; Yang, Quankui; Degreif, Kai; Schnürer, Frank

doi:10.1117/1.3506195

Cited by 68 publications

(36 citation statements)

References 29 publications

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“…Recently, stand-off spectroscopy using wavelength-tunable mid-IR lasers (e.g. quantum cascade lasers or narrow-linewidth OPOs) has been shown to provide sensitive detection of solid or gas samples at medium or long distances [13][14][15][16][17], however combining broad spectral coverage with rapid tuning still remains challenging. In this paper, we present the first implementation, to our knowledge, of active stand-off FTIR spectroscopy using a femtosecond OPO.…”

Section: Introductionmentioning

confidence: 99%

Active FTIR-based standoff detection in the 3-4 micron region using broadband femtosecond optical parametric oscillators

2014

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We present the first demonstration of stand-off Fourier transform infrared spectroscopy using a broadband mid-infrared femtosecond optical parametric oscillator, with spectral coverage over 2700-3200 cm -1 . Remote spectroscopy and chemical detection from 2700-3100 cm -1 is demonstrated for a thiodiglycol drop on concrete and anodized aluminum surfaces at a stand-off distance of 2 meters, as well as open-path spectroscopy of atmospheric water vapor from a concrete target at the same range. Comparison of the measured stand-off spectra with archived reference spectra for thiodiglycol and water vapor show good agreement. This technique provides greater spatial coherence and spectral brightness than a thermal source, and wider spectral coverage than a typical quantum-cascade laser, thereby presenting opportunities for application in the detection of industrial pollutants and the environmental identification of chemical warfare agents, explosives or other hazardous materials.

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Section: Introductionmentioning

confidence: 99%

Active FTIR-based standoff detection in the 3-4 micron region using broadband femtosecond optical parametric oscillators

2014

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“…More promising standoff detection that may be able to obtain IR spectral information from a substance is photothermal spectroscopy (PTS). There is a rich history of techniques based on PTS, [4][5][6][7][8][9][10][11][12][13][14][15] which have been of interest in detecting explosives 5,8,[13][14][15][16][17][18] food and water sensors, 19 and so on. The recent advancements in coherent IR sources such as the quantum cascade laser (QCL) 20 allow delivery of well-defined tunable beams in a precise range of wavelengths where IR absorption bands of interest reside.…”

Section: Introductionmentioning

confidence: 99%

Data analysis of multi-laser standoff spectral identification of chemical and biological compounds

Farahi

Zaharov²,

Tetard

et al. 2013

SPIE Proceedings

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With the availability of tunable broadband coherent sources that emit mid-infrared radiation with well-defined beam characteristics, spectroscopies that were traditionally not practical for standoff detection 1 or for development of miniaturized infrared detectors 2, 3 have renewed interest. While obtaining compositional information for objects from a distance remains a major challenge in chemical and biological sensing, recently we demonstrated that capitalizing on mid-infrared excitation of target molecules by using quantum cascade lasers and invoking a pump probe scheme can provide spectral fingerprints of substances from a variable standoff distance. 3 However, the standoff data is typically associated with random fluctuations that can corrupt the fine spectral features and useful data. To process the data from standoff experiments toward better recognition we consider and apply two types of denoising techniques, namely, spectral analysis and Karhunen-Loeve Transform (KLT). Using these techniques, infrared spectral data have been effectively improved. The result of the analysis illustrates that KLT can be adapted as a powerful data denoising tool for the presented pump-probe infrared standoff spectroscopy.

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“…Starting with a solution of 1 mg explosive dissolved in 1 ml of solvent (typically a 1:1 ratio of methanol and acetonitrile), we deposit one drop at a time onto either a gold mirror or roughened aluminum plate, allowing the solvent to evaporate. Each drop contains ~ 20 µg of solid material, which allows us to simulate first-generation fingerprint quantities of ~ 20-200 µg/cm 2 [8]. An image of the prepared gold mirror is shown in the inset of Fig.…”

Section: Introductionmentioning

confidence: 99%

A difference-frequency based mid-IR broadband source for surface spectroscopy of explosives

Nugent-Glandorf¹,

Neely²,

Johnson³

et al. 2011

2011 IEEE Photonics Society Summer Topical Meeting Series

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Abstract:We describe a 2.8 -4.4 µm tunable difference-frequency based mid-IR broadband source. With a FWHM of 170 nm centered at 3.3 µm, we have investigated the C-H stretch signatures of solid-phase trace explosives on surfaces.Mid-infrared (MIR) laser sources originating from femtosecond fiber lasers have gained recent attention as promising sources for molecular spectroscopy [1][2][3][4], combining broad spectral bandwidth and high resolution. In this study we also utilize the high brightness and power of a MIR laser to probe trace amounts of solid explosives on a surface using backscattered spectroscopy. A diagram of the MIR source is shown in Fig. 1(a). The 2.8 W amplified output of a Yb fiber laser, with 130 fs pulses and a 100 MHz repetition rate, is separated into two beams with a polarizing beamsplitter. A Raman-shifted soliton is formed in one arm by launching a portion of the power into a photonic crystal fiber (PCF). The soliton center wavelength can be tuned from 1.36 -1.66 m depending on the input power and polarization into the fiber [5]. MIR light is generated via simple difference frequency generation (DFG) in a 2-mm long fan-out periodically-poled lithium niobate (PPLN) crystal. The combination of the original laser output at 1.03 m and the Raman soliton results in an idler tunable from 2.8-4.4 µm, with a FWHM spectral width of ~170 nm, and average output power of up to 100 mW. Resulting MIR spectra are shown in Fig. 1(b). While this system has applications for high-resolution precision trace-gas spectroscopy [6], the low vapor pressure of explosives under typical environmental conditions makes the detection of outgassed molecules impractical for field applications [7]. We have thus begun to investigate the broadband spectroscopy of trace amounts of explosive residues deposited on surfaces, by examining the spectroscopic signature of MIR light scattered off the samples.By tuning the MIR laser center-wavelength to 3.3 µm the C-H stretch spectral region common to many organic molecules can be investigated. In particular, we have examined the high explosives RDX, HMX, Tetryl, and PETN. Starting with a solution of 1 mg explosive dissolved in 1 ml of solvent (typically a 1:1 ratio of methanol and acetonitrile), we deposit one drop at a time onto either a gold mirror or roughened aluminum plate, allowing the solvent to evaporate. Each drop contains ~ 20 µg of solid material, which allows us to simulate first-generation fingerprint quantities of ~ 20-200 µg/cm 2 [8]. An image of the prepared gold mirror is shown in the inset of Fig. 2(a).The optical system used to image scattered light from the explosive samples is shown in Fig. 2(a). The light from the laser system is directed at the solid sample, and a CaF 2 lens system is used to image scattered light to the input

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Imaging standoff detection of explosives using widely tunable midinfrared quantum cascade lasers

Cited by 68 publications

References 29 publications

Active FTIR-based standoff detection in the 3-4 micron region using broadband femtosecond optical parametric oscillators

Active FTIR-based standoff detection in the 3-4 micron region using broadband femtosecond optical parametric oscillators

Data analysis of multi-laser standoff spectral identification of chemical and biological compounds

A difference-frequency based mid-IR broadband source for surface spectroscopy of explosives

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