Widely tunable mode-hop free external cavity quantum cascade lasers for high resolution spectroscopy and chemical sensing

Wysocki, Gerard; Lewicki, R.; Curl, R. F.; Tittel, Frank K.; Diehl, Laurent; Capasso, Federico; Troccoli, Mariano; Höfler, G. E.; Bour, D. P.; Corzine, S.; Maulini, Richard; Giovannini, Marcella; Faist, Jérôme

doi:10.1007/s00340-008-3047-x

Cited by 200 publications

(120 citation statements)

References 25 publications

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“…In addition, detection of multi-species absorbers is possible by changing the ECL center wavelength. Overall, external cavity quantum cascade lasers (EC-QCLs) [13][14][15] represents a light source with high power, broad tuning range, narrow linewidth, and rapid wavelength tuning for the sensitive and accurate detection of trace gases like in breath analysis [16,17]. Examples of applications using EC-QCLs in narrowband absorption include detection of exhaled acetone [18,19], ammonia [20] and nitric oxide [21].…”

Section: Introductionmentioning

confidence: 99%

Influence of Ethanol on Breath Acetone Measurements Using an External Cavity Quantum Cascade Laser

et al. 2016

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Broadly tunable external cavity quantum cascade lasers (EC-QCLs) in combination with off-axis integrated cavity enhanced spectroscopy (OA-ICOS) provide high molecular gas sensitivity and selectivity. We used an EC-QCL in the region of 1150-1300 cm´1 in both broadband scan mode, as well as narrow scanning mode around 1216 cm´1, respectively, for detection of acetone in exhaled breath. This wavelength region is essential for accurate determination of breath acetone due to the relative low spectral influence of other endogenous molecules like water, carbon dioxide or methane. We demonstrated that ethanol has a strong spectroscopic influence on the acetone concentration in exhaled breath, an important detail that has been overlooked so far. An ethanol correction is proposed and validated with the reference measurements from a proton-transfer reaction mass spectrometer (PTR-MS) for the same breath samples from ten persons. With the ethanol correction, both broadband and narrowband molecular spectroscopy represent an attractive way to accurately assess the exhaled breath acetone. The importance of considering spectroscopic ethanol influence is essential, especially for the narrowband scans, (e.g., 1216 cm´1), for which the error in determining the acetone concentrations can rise up to 39% if it is not considered.

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Section: Introductionmentioning

confidence: 99%

Influence of Ethanol on Breath Acetone Measurements Using an External Cavity Quantum Cascade Laser

et al. 2016

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“…An External Cavity-Quantum Cascade Laser (EC-QCL) can be used which can achieve kHz scanning rates in a ∼ 7 cm −1 wavelength range or 20-40 Hz rates in a ≈ 100-150 cm −1 wavelength range. 40,41 Thermal isolation…”

Section: Acs Sensorsmentioning

confidence: 99%

On-Chip Mid-Infrared Photothermal Spectroscopy Using Suspended Silicon-on-Insulator Microring Resonators

et al. 2016

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Mid-infrared spectroscopic techniques rely on the specific ”fingerprint” absorption lines of molecules in the mid-infrared band to detect the presence and concentration of these molecules. Despite being very sensitive and selective, bulky and expensive equipment such as cooled mid-infrared detectors is required for conventional systems. In this paper, we demonstrate a miniature CMOS-compatible Silicon-on-Insulator (SOI) photothermal transducer for mid-infrared spectroscopy which can potentially be made in high volumes and at a low cost. The optical absorption of an analyte in the mid-infrared wavelength range (3.25–3.6 μm) is thermally transduced to an optical transmission change of a microring resonator through the thermo-optic effect in silicon. The photothermal signal is further enhanced by locally removing the silicon substrate beneath the transducer, hereby increasing the effective thermal isolation by a factor of 40. As a proof-of-concept, the absorption spectrum of a polymer that has been locally patterned in the annular region of the resonator was recovered using photothermal spectroscopy. The spectrum is in good agreement with a benchmark Fourier-transform infrared spectroscopy (FTIR) measurement. A normalized noise equivalent absorption coefficient (NNEA) of 7.6 × 10–6 cm–1 W/Hz1/2 is estimated.

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“…The expanded view in Figure 3b gives a close-up of one spectrum, for which the linewidth of the MOEMS EC-QCL can be determined to be 1.9 cm´1 at the 1/e 2 -cut (13.5%), or a corresponding FWHM of about 1.1 cm´1. It has to be noted that internal longitudinal modes of the QCL chip («0.4 cm´1 spacing for a chip length of 3.5 mm) are not separated in this measurement due to thermal chirp induced by intra pulse heating in pulsed operation [28] and the limited spectral resolution of the FTIR (0.2 cm´1). From the measurements presented in Figure 3 it is apparent that the linewidth, and thus the spectral resolution provided by the MOEMS EC-QCL remains constant at a value of 1.9 cm´1 over the whole spectral tuning range of the QCL chip.…”

Section: Determination Of the Spectral Linewidth And Wavelength Repromentioning

confidence: 99%

Recent Advances and Applications of External Cavity-QCLs towards Hyperspectral Imaging for Standoff Detection and Real-Time Spectroscopic Sensing of Chemicals

et al. 2016

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External-cavity quantum cascade lasers (EC-QCL) are now established as versatile wavelength-tunable light sources for analytical spectroscopy in the mid-infrared (MIR) spectral range. We report on the realization of rapid broadband spectral tuning with kHz scan rates by combining a QCL chip with a broad gain spectrum and a resonantly driven micro-opto-electro-mechanical (MOEMS) scanner with an integrated diffraction grating in Littrow configuration. The capability for real-time spectroscopic sensing based on MOEMS EC-QCLs is demonstrated by transmission measurements performed on polystyrene reference absorber sheets, as well as on hazardous substances, such as explosives. Furthermore, different applications for the EC-QCL technology in spectroscopic sensing are presented. These include the fields of process analysis with on-or even inline capability and imaging backscattering spectroscopy for contactless identification of solid and liquid contaminations on surfaces. Recent progress in trace detection of explosives and related precursors in relevant environments as well as advances in food quality monitoring by discriminating fresh and mold contaminated peanuts based on their MIR backscattering spectrum is shown.Keywords: quantum cascade lasers; external cavity quantum cascade lasers; MOEMS grating; quantum cascade laser based spectroscopy; imaging laser backscattering spectroscopy; inline spectroscopic analysis

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Widely tunable mode-hop free external cavity quantum cascade lasers for high resolution spectroscopy and chemical sensing

Cited by 200 publications

References 25 publications

Influence of Ethanol on Breath Acetone Measurements Using an External Cavity Quantum Cascade Laser

Influence of Ethanol on Breath Acetone Measurements Using an External Cavity Quantum Cascade Laser

On-Chip Mid-Infrared Photothermal Spectroscopy Using Suspended Silicon-on-Insulator Microring Resonators

Recent Advances and Applications of External Cavity-QCLs towards Hyperspectral Imaging for Standoff Detection and Real-Time Spectroscopic Sensing of Chemicals

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