Quantum Cascade Laser Based Photoacoustic Spectroscopy for Depth Profiling Investigations of Condensed-Phase Materials

Holthoff, Ellen L.; Marcus, Logan S.; Pellegrino, Paul M.

doi:10.1366/12-06655a

Cited by 7 publications

(16 citation statements)

References 41 publications

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“…The reference data was collected using a resonant PA cell where the resonant modes of the cell were used to amplify the acoustic signal to improve SNR. 9 The standoff data was collected without the benefit of cell based signal amplification at a modulation frequency higher than that of the cell based data. Spectral resolution of the standoff PA data is 2 cm -1 , and the cell based PA data has twice the resolution at 1 cm -1 .…”

Section: Resultsmentioning

confidence: 99%

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Photoacoustic chemical sensing: ultracompact sources and standoff detection

et al. 2014

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Photoacoustic spectroscopy (PAS) is a useful monitoring technique that is well suited for trace detection of gaseous and condensed media. We have previously demonstrated favorable PAS gas detection characteristics when the system dimensions are scaled to a micro-system design. This design includes quantum cascade laser (QCL)-based microelectromechanical systems (MEMS)-scale photoacoustic sensors that provide detection limits at parts-per-billion (ppb) levels for chemical targets. Current gas sensing research utilizes an ultra compact QCL, SpriteIR, in combination with a MEMS-scale photoacoustic cell for trace gas detection. At approximately one tenth the size of a standard commercially available QCL, SpriteIR is an essential element in the development of an integrated sensor package. We will discuss these results as well as the envisioned sensor prototype. Finally, expanding on our previously reported photoacoustic detection of condensed phase samples, we are investigating standoff photoacoustic chemical detection of these materials and will discuss preliminary results.

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Section: Resultsmentioning

confidence: 99%

“…8 In the realm of solid spectroscopy, PAS has been used for condensed phase sample interrogation and depth profiling in layered samples. 9 This versatility makes PAS one of the premier chemical sensing technologies.…”

Section: Introductionmentioning

confidence: 99%

Photoacoustic chemical sensing: ultracompact sources and standoff detection

et al. 2014

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“…7,8 Solid sample PAS has been shown to be a useful tool in depth profiling studies and standoff chemical detection. 9,10 It is in light of the versatility of PAS to examine solid samples at a standoff distance that we examine layered solid systems and the contribution to PA signal that is generated by the substrate in layered systems.…”

Section: Introductionmentioning

confidence: 99%

“…9 The remaining light, after considering surface reflection, is free to be absorbed by the substrate. We discuss the substrate response to the transmitted light from the excitation source.…”

Section: Introductionmentioning

confidence: 99%

Photoacoustic chemical sensing: layered systems and excitation source analysis

2015

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Photoacoustic spectroscopy (PAS) is a versatile tool that is well suited for the ranged interrogation of layered samples. We have previously demonstrated standoff photoacoustic (PA) chemical detection of condensed phase samples at one meter distance using an interferometric sensing platform. Current research investigates layered solid samples constructed from a thin layer of energetic material deposited on a substrate. The PA signal from the system, as measured by the interferometer, changes based on the differing optical and mechanical properties of the substrate. This signal variance must be understood in order to develop a sensor capable of detecting trace quantities of hazardous materials independent of the surface. Optical absorption and modal excitation are the two biggest sources of PA signal generated in the sample/substrate system. Finally, the mode of operation of the excitation source is investigated. Most PA sensing paradigms use a quantum cascade laser (QCL) operating in either pulsed or modulated CW mode. We will discuss photoacoustic signal generation with respect to these different operating modes.

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“…Also, a few research groups have made studies with solids [7][8][9][10][11]. However, to the best of our knowledge, this broad tuning range (676 cm -1 ) of an EC-QCL has never been used in the photoacoustic detection of solid samples.…”

Section: Introductionmentioning

confidence: 99%

Broadly tunable quantum cascade laser in cantilever-enhanced photoacoustic infrared spectroscopy of solids

Lehtinen

Kuusela

2013

Appl. Phys. B

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An external cavity quantum cascade laser (EC-QCL) is applied in the photoacoustic detection of solid samples. The EC-QCL used has a broad tuning range of 676 cm -1 (970-1,646 cm -1 ) in the mid-infrared region, which enables accurate broadband spectroscopy of large molecules. The high spectral power density of the EC-QCL is combined with an extremely sensitive optical cantilever microphone of the photoacoustic detector to achieve an ultimate sensitivity. The carbon black, polyethylene, and hair fiber samples were measured with the EC-QCL photoacoustic detection using electrical amplitude modulation to demonstrate the possibilities of the setup. The same measurements were repeated with a Fourier transform infrared (FTIR) spectrometer combined with a photoacoustic detector for a comparison. The EC-QCL photoacoustic setup yielded roughly a decade better signalto-noise ratios than the FTIR setup with the same measurement time.

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Quantum Cascade Laser Based Photoacoustic Spectroscopy for Depth Profiling Investigations of Condensed-Phase Materials

Cited by 7 publications

References 41 publications

Photoacoustic chemical sensing: ultracompact sources and standoff detection

Photoacoustic chemical sensing: ultracompact sources and standoff detection

Photoacoustic chemical sensing: layered systems and excitation source analysis

Broadly tunable quantum cascade laser in cantilever-enhanced photoacoustic infrared spectroscopy of solids

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