Application: Stand-off detection
Product: IRis-F1
M. Bredács, J. Geier, C. Barretta, R. Horvath, M. Geiser, K. Ander, G. Oreski and S. Gergely
Polymer Testing; 2023
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The high variety of tailor fitted molecular structures of polyethylene (PE) is very beneficial to fulfill requirements of various applications, however it poses a difficulty in the mechanical recycling of post-consumer PE products. To improve the quality of PE recyclates and increase the amounts of recyclates that can be used in new products, separation of PE waste by density and melt flow rate (MFR) during mechanical sorting is essential. Therefore, 25 virgin PE grades were used to manufacture compression molded plates that were then characterized by means of Attenuated Total Reflection - Fourier transformed IR (ATR-FTIR) and near IR (NIR) spectroscopy, NIR hyperspectral imaging and dual-comb spectroscopy. The results were used to build partial least squares regression (PLS) models to predict MFR and density. ATR-FTIR and laboratory NIR spectroscopy provided sufficient information to predict the density value of PE, whereas the MFR assessments was not possible. The PLS model from the industrial NIR data also only allowed the density-based classification of virgin PE grades. The PLS models built from transmission and reflectance dual comb spectroscopy infrared (DCS-IR) of selected samples clearly showed that density and MFR prediction can be carried out with high accuracy. As DCS-IR could be implemented on plastic sorting systems using a conveyor belt, the addition of this sensor in mechanical sorting line would lead to a significantly higher quality of recycled PE with narrow well-defined density and MFR ranges. Such an improvement would immensely support the targeted recycling rates and amount by the European Union and would make a significant step towards circular plastics.
Application: Time resolved vibrational spectroscopy
Product: IRis-F1
Karsten Hinrichs, Brianna Blevins, Andreas Furchner, Nataraja Yadavalli, Sergiy Minko, Raphael Horvath, Markus Mangold
Wiley Natural Sciences; 2023
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The mid-infrared (mid-IR) anisotropic optical response of a material probes vibrational fingerprints and absorption bands sensitive to order, structure and direction dependent stimuli. Such anisotropic properties play a fundamental role in catalysis, optoelectronic, photonic, polymer and biomedical research and applications. Infrared dual-comb polarimetry (IR-DCP) is introduced as a powerful new spectroscopic method for the analysis of complex dielectric functions and anisotropic samples in the mid-IR range. IR DCP enables novel hyperspectral and time-resolved applications far beyond the technical possibilities of classical Fourier-transform IR (FTIR) approaches. The method unravels structure–spectra relations at high spectral bandwidth (100 cm–1) and short integration times of 65 µs, with previously unattainable time resolutions for spectral IR polarimetric measurements for potential studies of noncyclic and irreversible processes. The polarimetric capabilities of IR-DCP are demonstrated by investigating an anisotropic inhomogeneous free-standing nanofiber scaffold for neural tissue applications. Polarization sensitive multi-angle dual-comb transmission amplitude and absolute phase measurements (separately for ss-, pp-, ps- and sp-polarized light) allow the in-depth probing of the samples’ orientation dependent vibrational absorption properties. Mid-IR anisotropies can be quickly identified by cross-polarized IR-DCP polarimetry.
Application: Gas analysis, High resolution spectroscopy, Time resolved vibrational spectroscopy
Product: IRis-F1
Josef A. Agner, Sieghard Albert, Pitt Allmendinger, Urs Hollenstein, Andreas Hugi, Pierre Jouy, Karen Keppler, Markus Mangold, Frédéric Merkt & Martin Quack
Molecular Physics; 2022
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Optical frequency-comb spectroscopy has proven a very useful tool for high-resolution molecular spectroscopy. Frequency combs based on quantum-cascade lasers (QCL) offer the possibility to easily explore the mid-infrared spectral range (4 µm to 12 µm), but are characterised by large repetition frequencies (∼ 10 GHz) which make them seemingly unsuitable for high-resolution spectroscopy. Here, we present techniques to overcome this limitation. We have employed the combined advantages of high temporal and high spectral resolution to measure the infrared (IR) spectra of CF4 and CHCl2F in pulsed, skimmed supersonic beams. The low rotational temperature of the beams and the narrow expansion cone after the skimmer enabled the recording of spectra of cold samples with high resolution. The spectra cover the range from 1200 cm−1 to 1290 cm−1 and the narrowest lines have a full width at half maximum of 15 MHz, limited by the Doppler effect. The results demonstrate the potential of QCL dual-comb spectroscopy for broadband (> 60 cm−1) acquisition of spectra at high spectral (better than 5·10−4 cm−1, 15 MHz) and temporal (better than 4 µs) resolution and high sensitivity in the mid-infrared range. The power of the new technology is demonstrated by comparison with previous results for these molecules obtained by FTIR and diode laser spectroscopy.
Application: Spectroelectrochemistry
Product: IRis-F1
Erick Lins, Ian R. Andvaag, Stuart Read, Scott M. Rosendahl, Ian J. Burgess
Journal of Electroanalytical Chemistry; 2022
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Attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) studies of the potential induced desorption/adsorption of a model organic monolayer is described using a paradigm-challenging dual frequency comb spectrometer. Experimentally measured ATR-SEIRAS transients reveal that both the rates of adsorption and desorption of 4-dimethylaminopyridine (DMAP) are dependent on the ionic strength of the supporting electrolyte. The characteristic time scales of monolayer desorption are found to be directly proportional to the spectroelectrochemical cell time constant indicating that the rate of film dissolution is much faster than the RC charging of the interface. The slow response of the interfacial charging process relative to the kinetics of the film re-organization/desorption processes means that the transient is parametrically linked to the potential dependent DMAP adsorption isotherm. The transients also reveal that the line shape of the molecular IR absorption feature exhibits a temporal dependence. A Lorentzian band is seen at early stages of the desorption transient but increasingly exhibit an anomalous bimodal line-shape at longer times. The development of the anomalous line shape is more pronounced at equivalent times in higher ionic strength electrolytes. Such an effect has been modelled using effective medium theory and is explained by the fact that the fraction of organic layer in the SEIRAS active film influences the observed apparent absorption features. The observation of a coverage dependence on SEIRAS line shapes adds new complexity to previous reports that linked anomalous absorption features exclusively to the metal film morphology and metal volume fraction.
Application: Photochemistry and photocatalysis, Protein dynamics, Time resolved vibrational spectroscopy
Product: IRis-F1
Luiz Schubert, Pit Langner, David Ehrenberg, Victor A. Lorenz-Fonfria, and Joachim Heberle
The Journal of Chemical Physics; 2022
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Mid-IR spectroscopy is a powerful and label-free technique to investigate protein reactions. In this study, we use quantum-cascade-laser-based dual-comb spectroscopy to probe protein conformational changes and protonation events by a single-shot experiment. By using a well-characterized membrane protein, bacteriorhodopsin, we provide a comparison between dual-comb spectroscopy and our homebuilt tunable quantum cascade laser (QCL)-based scanning spectrometer as tools to monitor irreversible reactions with high time resolution. In conclusion, QCL-based infrared spectroscopy is demonstrated to be feasible for tracing functionally relevant protein structural changes and proton translocations by single-shot experiments. Thus, we envisage a bright future for applications of this technology for monitoring the kinetics of irreversible reactions as in (bio-)chemical transformations.
Application: High resolution spectroscopy
Product: IRis-F1
Kenichi N. Komagata, Valentin J. Wittwer, Thomas Südmeyer, Lukas Emmenegger, Michele Gianella
Arxiv; 2022
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Quantum cascade laser (QCL) frequency combs have revolutionized mid-infrared (MIR) spectroscopy by their high brightness and fast temporal resolution, and are a promising technology for fully-integrated and cost-effective sensors. As for other integrated comb sources such as micro-combs and interband cascade laser, QCLs have a comb spacing of several GHz, which is adequate for measurements of wide absorbing structures, typically found in liquid or solid samples. However, high-resolution gas-phase spectra require spectral interleaving and frequency calibration. We developed a frequency calibration scheme for fast interleaved measurements with combs featuring multi-GHz spacing. We then demonstrate dual-comb spectroscopy with 600 kHz accuracy in single-shot 54-ms measurements over 40 cm−1 using two QCLs at 7.8 μm. This work is an important contribution towards fast fingerprinting of complex molecular mixtures in the MIR. Moreover, the calibration scheme could be used with micro-combs for spectroscopy and ranging, both in comb-swept and comb-calibrated setups.
Application: High resolution spectroscopy
Product: IRis-F1
Muriel Lepère, Olivier Browet, Jean Clément, Bastien Vispoel, Pitt Allmendinger, Jakob Hayden, Florian Eigenmann, Andreas Hugi, Markus Mangold
Journal of Quantitative Spectroscopy and Radiative Transfer; 2022
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To meet the challenges of high-resolution molecular spectroscopy, increasingly sophisticated spectroscopic techniques were developed. For a long time FTIR and laser-based spectroscopies were used for these studies. The recent development of dual-comb spectroscopy at high-resolution makes this technique a powerful tool for gas phase studies. We report on the use and characterization of the IRis-F1, a tabletop mid-infrared dual-comb spectrometer, in the newly developed step-sweep mode. The resolution of the wavenumber axis is increased by step-wise tuning (interleaving) and accurate measurement of the laser center wavelength and repetition frequency. Doppler limited measurements of N2O and CH4 reveal a wavenumber accuracy of 10−4 cm−1 on the covered range of > 50 cm−1. Measured half-widths of absorption lines show no systematic broadening, indicating a negligible instrument response function. Finally, measurements of nitrogen pressure broadening coefficients in the ν4 band of methane show that quantum cascade laser dual-comb spectroscopy in step-sweep mode is well adapted for measurements of precision spectroscopic data, in particular line shape parameters.
Application: Stand-off detection
Product: IRis-F1
John Macarthur, Jakob Hayden, Matthew S. Warden, Christopher Carson, David M. Stothard, Vasili G. Savitski
IEEE Transactions on Instrumentation and Measurement; 2022
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Standoff scanning dual-comb spectroscopy of explosive materials is demonstrated with quantum cascade lasers at ∼8 μm . The proof-of-concept of the spectrometer, capable of the detection and identification of explosive materials at a distance of 3 m, has a detection limit of cyclotrimethylenetrinitramine (RDX) and pentaerythritol tetranitrate (PETN) on various surfaces of 5– 8 μg /cm^2 in a scanning regime and 2– 3 μg /cm^2 with stationary beam in reflection–absorption and backscattering modes.
Application: High resolution spectroscopy
Product: IRis-core
Michele Gianella, Simon Vogel, Valentin Wittwer, Thomas Südmeyer, Jérôme Faist, Lukas Emmenegger
Optics Letters; 2022
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In dual-comb spectroscopy, there is a one-to-one map between the frequencies of the measured beat notes and the frequencies of the optical comb lines. Its determination usually involves the use of one or more reference lasers with known frequencies. Quantum cascade laser frequency combs, however, are often operated in a free-running mode, and without a reference, the determination of the RF-to-optical frequency map is not trivial. Here, we propose a method by which the comb shift is measured with an unbalanced Mach–Zehnder interferometer, and the spectral point spacing is determined through the intermode beat measured on the laser electrodes. The frequency axis is accurate within ∼ 0.001 cm−1.
Application: Combustion diagnostics
Product: IRis-F1
Nicolas Hunter Pinkowski, Pujan Biswas, Jiankun Shao, Christopher L Strand and Ronald K Hanson
Measurement Science and Technology; 2021
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Quantum-cascade-laserdual-comb spectroscopy (QCL-DCS) is a promising technology with ultra-fast time resolution capabilities for chemical kinetics, atmospheric gas sensing, and combustion applications. A pair of quantum-cascade frequency combs were used to measure absorbance from methane's 4 band between 1270 cm-1 and 1315 cm-1 at high-temperature and -pressure conditions that were generated using a high-pressure shock tube. Results here mark a major improvement over previous QCL-DCS measurements in shock tubes. Improvements came from a unique spectral-filtering strategy to correct for a bimodal power-spectral density of QCL frequency combs and careful optimization of the laser setup and experimental conditions. Our modified QCL-DCS was ultimately used to measure temperature within 2% and methane mole fraction within 5% by fitting HITEMP spectral simulations to spectra recorded at 4-μs temporal resolution. We measure temperature and species time-histories during methane pyrolysis at conditions between 1212-1980 K, and 12-17 atm, all at 4-μs resolution. Good agreement is observed with kinetic models, illustrating the potential of future applications of DCS in kinetics and combustion research.
Application: High resolution spectroscopy
Product: IRis-F1
K. Komagata, A. Shehzad, G. Terrasanta, P. Brochard, R. Matthey, M. Gianella, P. Jouy, F. Kapsalidis, M. Shahmohammadi, M. Beck, V. J. Wittwer, J. Faist, L. Emmenegger, T. Südmeyer, A. Hugi, and S. Schilt
Optics Express; 2021
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We demonstrate coherent averaging of the multi-heterodyne beat signal between two quantum cascade laser frequency combs in a master-follower configuration. The two combs are mutually locked by acting on the drive current to control their relative offset frequency and by radio-frequency extraction and injection locking of their intermode beat signal to stabilize their mode spacing difference. By implementing an analog common-noise subtraction scheme, a reduction of the linewidth of all heterodyne beat notes by five orders of magnitude is achieved compared to the free-running lasers. We compare stabilization and post-processing corrections in terms of amplitude noise. While they give similar performances in terms of signal-to-noise ratio, real-time processing of the stabilized signal is less demanding in terms of computational power. Lastly, a proof-of-principle spectroscopic measurement was performed, showing the possibility to reduce the amount of data to be processed by three orders of magnitude, compared to the free-running system.
Application: Photochemistry and photocatalysis, Protein dynamics, Time resolved vibrational spectroscopy
Product: IRis-F1
Mohamad Javad Norahan, Raphael Horvath, Nathalie Woitzik, Pierre Jouy, Florian Eigenmann, Klaus Gerwert and Carsten Koetting
ACS Analytical Chemistry; 2021
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Infrared spectroscopy is ideally suited for the investigation of protein reactions at the atomic level. Many systems were investigated successfully by applying Fourier transform infrared (FTIR) spectroscopy. While rapid-scan FTIR spectroscopy is limited by time resolution (about 10 ms with 16 cm-1 resolution), step-scan FTIR spectroscopy reaches a time-resolution of about 10 ns but is limited to cyclic reactions that can be repeated hundreds of times under identical conditions. Consequently, FTIR with high time resolution was only possible with photoactivable proteins that undergo a photocycle. The huge number of non-repetitive reactions, e.g. induced by caged compounds, were limited to the ms time domain. The advent of dual comb quantum cascade laser allows now for a rapid reaction monitoring in the μs time domain. Here we investigate the potential to apply such an instrument to the huge class of G-proteins. We compare caged-compound induced reactions monitored by FTIR and dual comb spectroscopy, respectively, by applying the new technique to the α subunit of the inhibiting Gi protein and to the larger protein-protein complex of Gαi with its cognate regulator of G-protein signaling (RGS). We observe good data quality with 4 μs time resolution with a wavelength resolution comparable to FTIR. This is more than three orders of magnitude faster than any FTIR measurement on G-proteins in the literature. This study paves the way for infrared spectroscopic studies in the so far unresolvable μs time regime for non-repetitive biological systems including all GTPases and ATPases.
Application: High resolution spectroscopy
Product: IRis-F1
Muriel Lepère, Olivier Browet, Sylvain Leonis, Jean Clément, Pitt Allmendinger, Kuno Knapp, Florian Eigenmann, Markus Mangold
SPIE Proceedings; 2021
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For a long time FTIR and laser-based spectroscopies have been used for high resolution molecular spectroscopy studies. The recent development of Dual-Comb Spectroscopy at high resolution (<0.001 cm-1) makes this technique a powerful tool for gas phase studies. The IRis-F1 is a dual-comb spectrometer building on quantum cascade laser frequency combs. We show that it is very well adapted for measurements of line shape parameters. Despite its weak abundance, methane effect on climate and atmospheric chemistry is important. We measured with IRis-F1 the half-widths of absorption lines of methane diluted in nitrogen, and compared with results obtained by other spectroscopies.
Application: Protein dynamics, Stopped flow and microfluidics
Product: IRis-F1
Markus Geiser, Raphael Horvath and Jakob Hayden
Photonics Views; 2021
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Dual‐comb spectroscopy is a powerful direct absorption spectroscopy technique and has attracted considerable attention, with high precision spectroscopy applications being the most prominent since the invention of the frequency comb was awarded the 2005 Nobel Prize in physics. The application range is continuously broadening and here we review recent advances achieved with quantum cascade laser frequency comb spectrometers in process monitoring and reaction kinetics applications.
Application: Combustion diagnostics, Gas analysis, Shock tubes and rapid compression machines, Time resolved vibrational spectroscopy
Product: IRis-F1
Peter Fjodorow, Pitt Allmendinger, Raphael Horvath, Jürgen Herzler, Florian Eigenmann, Markus Geiser, Mustapha Fikri and Christof Schulz
Applied Physics B volume 126, Article number: 193; 2020
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A dual-frequency-comb spectrometer based on two quantum-cascade lasers is applied to kinetics studies of formaldehyde (HCHO) in a shock tube. Multispectral absorption measurements are carried out in a broad spectral range of 1740–1790 cm–1 at temperatures of 800–1500 K and pressures of 2–3 bar. The formation of HCHO from thermal decomposition of 1,3,5-trioxane (C3H6O3, 0.9% diluted in argon) and the subsequent oxidation of formaldehyde is monitored with a time resolution of 4 µs. The rate coefficient of the decomposition of C3H6O3 (i.e., HCHO formation) is found to be k1 = 6.0 × 1015 exp(− 205.58 kJ mol−1/RT) s–1. For the oxidation studies, mixtures of 0.36% C3H6O3 and 1% O2 in argon are used. The information of all laser lines, along with the consideration of individual signal variance of each line, is utilized for kinetic and spectral analysis. The experimental kinetic profiles of HCHO are compared with simulations based on the mechanisms of Zhou et al. (Combust Flame, 197:423–438, 2018) and Cai and Pitsch (Combust Flame, 162:1623–1637, 2015).
Application: Combustion diagnostics, High resolution spectroscopy
Product: IRis-F1
Nicolas Hunter Pinkowski, Sean Joseph Cassady, Christopher L Strand and Ronald K Hanson
Measurement Science and Technology; 2020
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This work presents a methodology for using spectroscopic models to fit absorption-spectrum measurements made by a quantum-cascade-laser-based dual-comb (QCL-DCS) spectrometer for high-temperature kinetics research. A pair of quantum-cascade frequency combs was employed to detect methane's ν4 absorption features between 1270-1320 cm-1 in high-temperature shock-tube environments and extract methane mole fraction and gas temperature from the results. The methodology was first validated by comparing DCS measurements against modeled methane spectra at room temperature in a static cell, followed by assessing the fitting procedure in shock-heated mixtures of 2% methane in Ar at 1000 K. In both validation experiments, the tradeoffs between time resolution and measurement precision were explored. Measurements were achieved at a 4-μs measurement rate with 5% uncertainty for temperature and 4% uncertainty for mole fraction at 1000 K. Higher accuracy was achieved with longer measurement averaging, e.g. 1.8% uncertainty for temperature at 40-μs resolution. Finally, the DCS spectral-fitting methodology was demonstrated to capture temperature and methane time-history evolution during the pyrolysis of iso-octane, a primary gasoline reference fuel. Good agreement was observed with kinetic models, and future applications for DCS kinetics research are discussed.
Application: Gas analysis
Product: IRis-F1
Ramin Ghorbani, Anders Blomberg and Florian M Schmidt
Journal of Breath Research, Volume 14, Number 4; 2020
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The influence of breath sampling on exhaled carbon monoxide (eCO) and related pulmonary gas exchange parameters is investigated in a study with 32 healthy non-smokers. Mid-infrared tunable diode laser absorption spectroscopy and well-controlled online sampling is used to precisely measure mouth- and nose-exhaled CO expirograms at exhalation flow rates (EFRs) of 250, 120 and 60 ml s−1, and for 10 s of breath-holding followed by exhalation at 120 ml s−1. A trumpet model with axial diffusion is employed to fit simulated exhalation profiles to the experimental expirograms, which provides equilibrium airway and alveolar CO concentrations and the average lung diffusing capacity in addition to end-tidal concentrations. For all breathing maneuvers, excellent agreement is found between mouth- and nose-exhaled end-tidal CO (ETCO), and the individual values for ETCO and alveolar diffusing capacity are consistent across maneuvers. The eCO parameters clearly show a dependence on EFR, where the lung diffusing capacity increases with EFR, while ETCO slightly decreases. End-tidal CO is largely independent of ambient air CO and alveolar diffusing capacity. While airway CO is slightly higher than, and correlates strongly with, ambient air CO, and there is a weak correlation with ETCO, the results point to negligible endogenous airway CO production in healthy subjects. An EFR of around 120 ml s−1 can be recommended for clinical eCO measurements. The employed method provides means to measure variations in endogenous CO, which can improve the interpretation of exhaled CO concentrations and the diagnostic value of eCO tests in clinical studies.
Application: Time resolved vibrational spectroscopy
Product: IRis-F1
Dr. Florian Eigenmann and Dr. Raphael Horvath
China Coatings Journal; 2020
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Application: Combustion diagnostics, Shock tubes and rapid compression machines, Time resolved vibrational spectroscopy
Product: IRis-F1
Guangle Zhang, Raphael Horvath, Dapeng Liu, Markus Geiser, Aamir Farooq
Sensors, MDPI; 2020
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Rapid multi-species sensing is an overarching goal in time-resolved studies of chemical kinetics. Most current laser sources cannot achieve this goal due to their narrow spectral coverage and/or slow wavelength scanning. In this work, a novel mid-IR dual-comb spectrometer is utilized for chemical kinetic investigations. The spectrometer is based on two quantum cascade laser frequency combs and provides rapid (4 µs) measurements over a wide spectral range (~1175–1235 cm−1). Here, the spectrometer was applied to make time-resolved absorption measurements of methane, acetone, propene, and propyne at high temperatures (>1000 K) and high pressures (>5 bar) in a shock tube. Such a spectrometer will be of high value in chemical kinetic studies of future fuels.
Application: Spectroelectrochemistry, Time resolved vibrational spectroscopy
Product: IRis-F1
Lins, E.; Read, S.; Unni, B.; Rosendahl, S. M.; Burgess, I. J.
Analytical Chemistry; 2020
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A dual infrared frequency comb spectrometer with heterodyne detection has been used to perform time-resolved electrochemical attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS). The measurement of the potential dependent desorption of a monolayer of a pyridine derivative (4-dimethylaminopyridine, DMAP) with time resolution as high as 4 μs was achieved without the use of step-scan interferometry. An analysis of the detection limit of the method as a function of both time resolution and measurement coadditions is provided and compared to step-scan experiments of an equivalent system. Dual frequency comb spectroscopy is shown to be highly amenable to time-resolved ATR-SEIRAS. Microsecond resolved spectra can be obtained with high spectral resolution and fractional monolayer detection limits in a total experimental duration that is 2 orders of magnitude less than the equivalent step-scan experiment.
Application: Combustion diagnostics, Shock tubes and rapid compression machines, Time resolved vibrational spectroscopy
Product: IRis-F1
Pinkowski, Nicolas Hunter; Ding, Yiming; Strand, Christopher L.; Hanson, Ronald K.; Horvarth, Raphael; Geiser, Markus
Measurement Science and Technology; 2020
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In the current study, a quantum-cascade-laser-based dual-comb spectrometer (DCS) was used to paint a detailed picture of a 1.0 ms high-temperature reaction between propyne and oxygen. The DCS interfaced with a shock tube to provide pre-ignition conditions of 1225 K, 2.8 atm, and 2% p-C3H4/18% O2/Ar. The spectrometer consisted of two free-running, non-stabilized frequency combs each emitting at 179 wavelengths between 1174 and 1233 cm−1. A free spectral range, {f_r}, of 9.86 GHz and a difference in comb spacing, {Delta }{f_r}, of 5 MHz, enabled a theoretical time resolution of 0.2 µs but the data was time-integrated to 4 µs to improve SNR. The accuracy of the spectrometer was monitored using a suite of independent laser diagnostics and good agreement observed. Key challenges remain in the fitting of available high-temperature spectroscopic models to the observed spectra of a post-ignition environment.
Application: High resolution spectroscopy
Product: IRis-F1
Gianella, Michele; Nataraj, Akshay; Tuzson, Béla; Jouy, Pierre; Kapsalidis, Filippos; Beck, Mattias; Mangold, Markus; Hugi, Andreas; Faist, Jérôme; Emmenegger, Lukas
Optics Express, Optical Society of America; 2020
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We present gapless, high-resolution absorption and dispersion spectra obtained with quantum cascade laser frequency combs covering 55 cm−1. Using phase-sensitive dual comb design, the comb lines are gradually swept over 10 GHz, corresponding to the free spectral range of the laser devices, by applying a current modulation. We show that with interleaving the spectral point spacing is reduced by more than four orders of magnitude over the full spectral span of the frequency comb. The potential of this technique for high-precision gas sensing is illustrated by measuring the low pressure (107 hPa) absorption and dispersion spectra of methane spanning the range of 1170 cm−1 - 1225 cm−1 with a resolution of 0.001 cm−1.
Application: Electrochromism
Product: IRis-F1
Szczepaniak, Urszula; Schneider, Samuel Hayes; Horvath, Raphael; Kozuch, Jacek; Geiser, Markus
Applied Spectroscopy, SAGE Publications; 2019
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We demonstrate the performance of a dual frequency comb quantum cascade laser (QCL) spectrometer for the application of vibrational Stark spectroscopy. Measurements performed on fluorobenzene with the dual-comb spectrometer (DCS) were compared to results obtained using a conventional Fourier transform infrared (FT-IR) instrument in terms of spectral response, parameter estimation, and signal-to-noise ratio (S/N). The dual-comb spectrometer provided similar qualitative and quantitative data as the FT-IR setup in 250 times shorter acquisition time. For fluorobenzene, the DCS measurement resulted in a more precise estimation of the fluorobenzene Stark tuning rate ((0.81 ± 0.09) cm−1/(MV/cm)) than with the FT-IR system ((0.89 ± 0.15) cm−1/(MV/cm)). Both values are in accordance with the previously reported value of 0.84 cm−1/(MV/cm). We also point to an improvement of signal-to-noise ratio in the DCS configuration. Additional characteristics of the dual-comb spectrometer applicable to vibrational Stark spectroscopy and their scaling properties for future applications are discussed.
Application: Protein dynamics
Product: IRis-F1
Schubert, Luiz
Presentation at ECSBM 2019; 2019
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Application: Combustion diagnostics, Shock tubes and rapid compression machines, Time resolved vibrational spectroscopy
Product: IRis-F1
Pinkowski, N.; Strand, C. L.; Ding, Y.; Hanson, R. K.; Geiser, M.; Horvath, R.
Presentation at ISSW32; 2019
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Application: High resolution spectroscopy
Product: IRis-F1
Shehzad, A.; Brochard, P.; Matthey, R.; Kapsalidis, F.; Shahmohammadi, M.; Beck, M.; Hugi, A.; Jouy, P.; Faist, J.; Südmeyer, T.; Schilt, S.
Optics Express, Optical Society of America; 2019
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The generation of frequency combs in the mid-infrared (MIR) spectral range by quantum cascade lasers (QCLs) has the potential for revolutionizing dual-comb multi-heterodyne spectroscopy in the molecular fingerprint region. However, in contrast to frequency combs based on passively mode-locked ultrafast lasers, their operation relies on a completely different mechanism resulting from a four-wave mixing process occurring in the semiconductor gain medium that locks the modes together. As a result, these lasers do not emit pulses and no direct self-referencing of a QCL comb spectrum has been achieved so far. Here, we present a detailed frequency noise characterization of a MIR QCL frequency comb operating at a wavelength of 8 µm with a mode spacing of ∼7.4 GHz. Using a beat measurement with a narrow-linewidth single-mode QCL in combination with a dedicated electrical scheme, we measured the frequency noise properties of an optical mode of the QCL comb, and indirectly of its offset frequency for the first time, without detecting it by the standard approach of nonlinear interferometry applied to ultrafast mode-locked lasers. In addition, we also separately measured the noise of the comb mode spacing extracted electrically from the QCL. We observed a strong anti-correlation between the frequency fluctuations of the offset frequency and mode spacing, leading to optical modes with a linewidth slightly below 1 MHz in the free-running QCL comb (at 1-s integration time), which is narrower than the individual contributions of the offset frequency and mode spacing that are at least 2 MHz each.
Application: Gas analysis
Product: IRis-F1
Ramin Ghorbani and Florian M Schmidt
Journal of Breath Research, Volume 13, Number 2; 2019
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Real-time breath gas analysis coupled to gas exchange modeling is emerging as promising strategy to enhance the information gained from breath tests. It is shown for exhaled breath carbon monoxide (eCO), a potential biomarker for oxidative stress and respiratory diseases, that a weighted, nonlinear least-squares fit of simulated to measured expirograms can be used to extract physiological parameters, such as airway and alveolar concentrations and diffusing capacities. Experimental CO exhalation profiles are acquired with high time-resolution and precision using mid-infrared tunable diode laser absorption spectroscopy and online breath sampling. A trumpet model with axial diffusion is employed to generate eCO profiles based on measured exhalation flow rates and volumes. The concept is demonstrated on two healthy non-smokers exhaling at a flow rate of 250 ml s−1 during normal breathing and at 120 ml s−1 after 10 s of breath-holding. The obtained gas exchange parameters of the two subjects are in a similar range, but clearly distinguishable. Over a series of twenty consecutive expirograms, the intra-individual variation in the alveolar parameters is less than 6%. After a 2 h exposure to 10 ± 2 ppm CO, end-tidal and alveolar CO concentrations are significantly increased (by factors of 2.7 and 4.9 for the two subjects) and the airway CO concentration is slightly higher, while the alveolar diffusing capacity is unchanged compared to before exposure. Using model simulations, it is found that a three-fold increase in maximum airway CO flux and a reduction in alveolar diffusing capacity by 60% lead to clearly distinguishable changes in the exhalation profile shape. This suggests that extended breath CO analysis has clinical relevance in assessing airway inflammation and chronic obstructive pulmonary disease. Moreover, the novel methodology contributes to the standardization of real-time breath gas analysis.
Application: Photochemistry and photocatalysis, Protein dynamics
Product: IRis-F1
Klocke, Jessica L.; Mangold, Markus; Allmendinger, Pitt; Hugi, Andreas; Geiser, Markus; Jouy, Pierre; Faist, Jérôme; Kottke, Tilman
Analytical Chemistry, American Chemical Society; 2018
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The kinetic analysis of irreversible protein reactions requires an analytical technique that provides access to time-dependent infrared spectra in a single shot. Here, we present a spectrometer based on dual-frequency-comb spectroscopy using mid-infrared frequency combs generated by quantum cascade lasers. Attenuation of the intensity of the combs by molecular vibrational resonances results in absorption spectra covering 55 cm–1 in the fingerprint region. The setup has a native resolution of 0.3 cm–1, noise levels in the μOD range, and achieves sub-microsecond time resolution. We demonstrate the simultaneous recording of both spectra and transients of the photoactivated proton pump bacteriorhodopsin. More importantly, a single shot, i.e., a single visible light excitation, is sufficient to extract spectral and kinetic characteristics of several intermediates in the bacteriorhodopsin photocycle. This development paves the way for the noninvasive analysis of enzymatic conversions with high time resolution, broad spectral coverage, and minimal sample consumption.
Application: Protein dynamics
Product: IRis-F1
Dutton, Gail
Genetic Engineering & Biotechnology News; 2018
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Application: Stand-off detection
Product: IRis-F1
Hensley, Joel M.; Brown, Justin M.; Allen, Mark G.; Geiser, Markus; Allmendinger, Pitt; Mangold, Markus; Hugi, Andreas; Juoy, Pierre; Faist, Jérôme
Ultrafast Bandgap Photonics III; 2018
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Using dual optical frequency comb (OFC) spectroscopy in the longwave infrared (LWIR), we demonstrate standoff detection of trace amounts of target compounds on diffusely scattering surfaces. The OFC is based on quantum cascade lasers (QCL) that emit ~1 Watt of optical power under cw operation at room temperature over coherent comb bandwidths approaching 100 cm-1. We overlap two nearly identical 1250 cm-1 QCL OFC sources so that the two interfering optical combs create via heterodyne a single comb in the radio frequency (rf) that represents the entire optical spectrum in a single acquisition. In a laboratory scale demonstration we show detection of two spectrally distinct fluorinated silicone oils, poly(methyl-3,3,3-trifluoropropylsiloxane) and Krytox™, that act as LWIR simulants for security relevant compounds whose room temperature vapor pressure is too low to be detected in the gas phase. These target compounds are applied at mass loadings of 0.3 to 90 μg/cm2 to sanded aluminum surfaces. Only the diffusely scattered light is collected by a primary collection optic and focused onto a high speed (0.5 GHz bandwidth) thermoelectrically cooled mercury cadmium telluride (MCT) detector. At standoff distances of both 0.3 and 1 meter, we demonstrate 3 μg/cm2 and 1 μg/cm2 detection limits against poly(methyl-3,3,3-trifluoropropylsiloxane) and Krytox™, respectively.
Application: Photochemistry and photocatalysis, Protein dynamics, Time resolved vibrational spectroscopy
Product: IRis-F1
Geiser, Markus; Klocke, Jessica L.; Mangold, Markus; Allmendinger, Pitt; Hugi, Andreas; Jouy, Pierre; Horvath, Balint; Faist, Jerome; Kottke, Tilman
Biophysical Journal, Elsevier; 2018
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Time-resolved vibrational spectroscopy is an important tool for understanding biological processes and chemical reaction pathways. Today, all available methods to our knowledge require many repetitions of an experiment to acquire a microsecond time-res. mid-IR spectrum. We present the IRspectrometer, a quantum cascade laser dual frequency comb spectrometer. It allows for parallel acquisition of hundreds of mid-infrared wavelengths with microsecond time resolution. The formation of the light-activated L, M and N-states in bacteriorhodopsin - which only have µs to ms lifetimes - has been recorded with our setup: e.g. infrared response of bacteriorhodopsin to 10 ns visible light pulses with microsecond time-resolution. The different wavelengths were all measured in parallel thanks to the dual-comb approach. The spectra as well as the kinetics show good agreement with those from step-scan FTIR measurements. As a benchmark, the spectral signature of several intermediate states of the bacteriorhodopsin photocycle has been recorded in a single shot measurement. This approach greatly reduces the complexity of time-resolved bio-spectroscopy measurements in the mid-infrared which currently require many repetitions.
Application: Gas analysis
Product: IRcell-S
Ghorbani, Ramin; Schmidt, Florian M.
Optics Express, Optical Society of America; 2017
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We present a compact sensor for carbon monoxide (CO) in air and exhaled breath based on a room temperature interband cascade laser (ICL) operating at 4.69 µm, a low-volume circular multipass cell and wavelength modulation absorption spectroscopy. A fringe-limited (1σ) sensitivity of 6.5 × 10−8 cm−1Hz-1/2 and a detection limit of 9 ± 5 ppbv at 0.07 s acquisition time are achieved, which constitutes a 25-fold improvement compared to direct absorption spectroscopy. Integration over 10 s increases the precision to 0.6 ppbv. The setup also allows measuring the stable isotope 13CO in breath. We demonstrate quantification of indoor air CO and real-time detection of CO expirograms from healthy non-smokers and a healthy smoker before and after smoking. Isotope ratio analysis indicates depletion of 13CO in breath compared to natural abundance.
Application: Gas analysis
Product: IRis-F1
Ghorbani, Ramin; Schmidt, Florian M.
Applied Physics B; 2017
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Real-time breath gas analysis is a promising, non-invasive tool in medical diagnostics, and well-suited to investigate the physiology of carbon monoxide (CO), a potential biomarker for oxidative stress and respiratory diseases. A sensor for precise, breath-cycle resolved, simultaneous detection of exhaled CO (eCO) and carbon dioxide (eCO2) was developed based on a continuous wave, external-cavity quantum cascade laser (EC-QCL), a low-volume multi-pass cell and wavelength modulation spectroscopy. The system achieves a noise-equivalent (1σ) sensitivity of 8.5 × 10−8 cm−1 Hz−1/2 and (2σ) detection limits of 9 ± 2 ppbv and 650 ± 7 ppmv at 0.14 s spectrum acquisition time for CO and CO2, respectively. Integration over 15 s yields a precision of 0.6 ppbv for CO. The fact that the eCO2 expirograms measured by capnography and laser spectroscopy have essentially identical shape confirms true real-time detection. It is found that the individual eCO exhalation profiles from healthy non-smokers have a slightly different shape than the eCO2 profiles and exhibit a clear dependence on exhalation flow rate and breath-holding time. Detection of indoor air CO and broadband breath profiling across the 93 cm−1 mode-hop-free tuning range of the EC-QCL are also demonstrated.
Application: High resolution spectroscopy
Product: IRis-F1
Gustavo Villares, Andreas Hugi, Stéphane Blaser & Jérôme Faist
Nature Communications; 2014
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Dual-comb spectroscopy performed in the mid-infrared—where molecules have their strongest rotovibrational absorption lines—offers the promise of high spectral resolution broadband spectroscopy with very short acquisition times (μs) and no moving parts. Recently, we demonstrated frequency comb operation of a quantum-cascade-laser. We now use that device in a compact, dual-comb spectrometer. The noise properties of the heterodyne beat are close to the shot noise limit. Broadband (15 cm−1) high-resolution (80 MHz) absorption spectroscopy of both a GaAs etalon and water vapour is demonstrated, showing the potential of quantum-cascade-laser frequency combs as the basis for a compact, all solid-state, broadband chemical sensor.
Application: Gas analysis
Product: IRcell-S
Jouy, P.; Mangold, M.; Tuzson, B.; Emmenegger, L.; Chang, Y.; Hvozdara, L.; Herzig, H. P.; Wägli, P.; Homsy, A.; Rooij, N. F.; Wirthmueller, A.; Hofstetter, D.; Looserg, H.; Faista, J.
Analyst; 2014
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In this paper we present two compact, quantum cascade laser absorption spectroscopy based, sensors developed for trace substance detection in gases and liquids. The gas sensor, in its most integrated version, represents the first system combining a quantum cascade laser and a quantum cascade detector. Furthermore, it uses a toroidal mirror cell with a volume of only 40 cm3 for a path length of up to 4 m. The analytical performance is assessed by the measurements of isotope ratios of CO2 at ambient abundance. For the 13CO2/12CO2 isotope ratio, a measurement precision of 0.2‰ is demonstrated after an integration time of 600 s. For the liquid sensor, a microfluidic system is used to extract cocaine from saliva into a solvent (PCE) transparent in the mid-infrared. This system is bonded on top of a Si/Ge waveguide and the concentration of cocaine in PCE is measured through the interaction of the evanescent part of the waveguide optical mode and the solvent flowing on top. A detection limit of <100 μg mL−1 was achieved with this system and down to 10 μg mL−1 with a simplified, but improved system.
Application: Gas analysis
Product: IRcell-S
Tuzson, B.; Mangold, M.; Looser, H.; Manninen, A.; Emmenegger, L.
Optical Society of America; 2013
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A multipass cell (MPC) design for laser absorption spectroscopy is presented. The development of this new type of optical cell was driven by stringent criteria for compactness, robustness, low volume, and ease of use in optical systems. A single piece of reflective toroidal surface forms a near-concentric cavity with a volume of merely 40 cm³. Contrary to traditional MPCs, this design allows for flexible path-length adjustments by simply changing the aiming angle of the laser beam at the entrance window. Two effective optical path lengths of 2.2 and 4.1 m were chosen to demonstrate the cell’s suitability for high-precision isotope ratio measurements of CO2 at 1% and ambient mixing ratio levels.