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Timeline of Markus Sigrist

2018
Jun
01
Published new article




Article

Frequency stabilization of quantum cascade laser for spectroscopic CO 2 isotope analysis

Published: 01 June 2018 by Elsevier BV in Infrared Physics & Technology

doi: 10.1016/j.infrared.2018.03.016

1 Reads | 2 Citations
2017
Jul
14
Published new article




Article

Fiber optic distributed temperature sensing for fire source localization

Published: 14 July 2017 by IOP Publishing in Measurement Science and Technology

doi: 10.1088/1361-6501/aa7436

A method for localizing a fire source based on a distributed temperature sensor system is proposed. Two sections of optical fibers were placed orthogonally to each other as the sensing elements. A tray of alcohol was lit to act as a fire outbreak in a cabinet with an uneven ceiling to simulate a real scene of fire. Experiments were carried out to demonstrate the feasibility of the method. Rather large fluctuations and systematic errors with respect to predicting the exact room coordinates of the fire source caused by the uneven ceiling were observed. Two mathematical methods (smoothing recorded temperature curves and finding temperature peak positions) to improve the prediction accuracy are presented, and the experimental results indicate that the fluctuation ranges and systematic errors are significantly reduced. The proposed scheme is simple and appears reliable enough to locate a fire source in large spaces.

0 Reads | 2 Citations
2016
Oct
10
Published new article




Article

Mid-Infrared Photoacoustic Detection of Glucose in Human Skin: Towards Non-Invasive Diagnostics

Published: 10 October 2016 by MDPI in Sensors

doi: 10.3390/s16101663

Diabetes mellitus is a widespread metabolic disease without cure. Great efforts are being made to develop a non-invasive monitoring of the blood glucose level. Various attempts have been made, including a number of non-optical approaches as well as optical techniques involving visible, near- and mid-infrared light. However, no true breakthrough has been achieved so far, i.e., there is no fully non-invasive monitoring device available. Here we present a new study based on mid-infrared spectroscopy and photoacoustic detection. We employ two setups, one with a fiber-coupled photoacoustic (PA) cell and a tunable quantum cascade laser (QCL), and a second setup with two QCLs at different wavelengths combined with PA detection. In both cases, the PA cells are in direct skin contact. The performance is tested with an oral glucose tolerance test. While the first setup often gives reasonable qualitative agreement with ordinary invasive blood glucose measurements, the dual-wavelength approach yields a considerably improved stability and an uncertainty of only ±30 mg/dL of the blood glucose concentration level at a confidence level of 90%. This result is achieved without advanced data treatment such as principal component analysis involving extended wavelength ranges.

0 Reads | 10 Citations
2016
Oct
01
Published new article




Article

Investigation of effective line intensities of trans-HONO near 1255 cm −1 using continuous-wave quantum cascade laser sp...

Published: 01 October 2016 by Elsevier BV in Journal of Quantitative Spectroscopy and Radiative Transfer

doi: 10.1016/j.jqsrt.2016.06.014

Highlights•Effective line strengths of trans-HONO between 1251.8 and 1257.2 cm−1.•Comparison to previous line strength data reported in literature.•Synthetization and calibration of concentration of gaseous HONO samples•Sub-ppb HONO detection limit. AbstractEffective line intensities of P branch transitions of trans-nitrous acid (HONO) in the ν3 H-O-N bending mode near 1255 cm−1 have been determined by both tunable diode laser absorption spectroscopy (TDLAS) and the scaling reference method with continuous-wave quantum cascade lasers (cw-QCL). Gaseous HONO samples were synthetized in the laboratory using the reaction of H2SO4 and NaNO2 solutions and the heterogeneous formation on surfaces in the presence of ambient water vapor and NO2 gas in a sealed gas sampling bag. The quantification of HONO was performed using a denuder associated with a NOx analyzer. Observed absorption line strengths for the trans conformer are found to be by a factor of approximately 1.17 higher than previously reported line strengths.

1 Reads | 2 Citations
2016
Jul
19
Published new article




Article

Reconstruction of combustion temperature and gas concentration distributions using line-of-sight tunable diode laser abs...

Published: 19 July 2016 by SPIE-Intl Soc Optical Eng in Optical Engineering

doi: 10.1117/1.oe.55.7.076107

. Spatial temperature and gas concentration distributions are crucial for combustion studies to characterize the combustion position and to evaluate the combustion regime and the released heat quantity. Optical computer tomography (CT) enables the reconstruction of temperature and gas concentration fields in a flame on the basis of line-of-sight tunable diode laser absorption spectroscopy (LOS-TDLAS). A pair of H2O absorption lines at wavelengths 1395.51 and 1395.69 nm is selected. Temperature and H2O concentration distributions for a flat flame furnace are calculated by superimposing two absorption peaks with a discrete algebraic iterative algorithm and a mathematical fitting algorithm. By comparison, direct absorption spectroscopy measurements agree well with the thermocouple measurements and yield a good correlation. The CT reconstruction data of different air-to-fuel ratio combustion conditions (incomplete combustion and full combustion) and three different types of burners (one, two, and three flat flame furnaces) demonstrate that TDLAS has the potential of short response time and enables real-time temperature and gas concentration distribution measurements for combustion diagnosis.

1 Reads | 1 Citations
2016
Jun
06
Published new article




Article

Fire Source Localization Based on Distributed Temperature Sensing by a Dual-Line Optical Fiber System

Published: 06 June 2016 by MDPI in Sensors

doi: 10.3390/s16060829

We propose a method for localizing a fire source using an optical fiber distributed temperature sensor system. A section of two parallel optical fibers employed as the sensing element is installed near the ceiling of a closed room in which the fire source is located. By measuring the temperature of hot air flows, the problem of three-dimensional fire source localization is transformed to two dimensions. The method of the source location is verified with experiments using burning alcohol as fire source, and it is demonstrated that the method represents a robust and reliable technique for localizing a fire source also for long sensing ranges.

0 Reads | 3 Citations
2016
Jun
02
Published new article




Article

Laser-induced breakdown spectroscopy applied to the characterization of rock by support vector machine combined with pri...

Published: 02 June 2016 by IOP Publishing in Chinese Physics B

doi: 10.1088/1674-1056/25/6/065201

Laser-induced breakdown spectroscopy (LIBS) is a versatile tool for both qualitative and quantitative analysis. In this paper, LIBS combined with principal component analysis (PCA) and support vector machine (SVM) is applied to rock analysis. Fourteen emission lines including Fe, Mg, Ca, Al, Si, and Ti are selected as analysis lines. A good accuracy (91.38% for the real rock) is achieved by using SVM to analyze the spectroscopic peak area data which are processed by PCA. It can not only reduce the noise and dimensionality which contributes to improving the efficiency of the program, but also solve the problem of linear inseparability by combining PCA and SVM. By this method, the ability of LIBS to classify rock is validated.

1 Reads | 3 Citations
2016
May
16
Published new article




Article

Development of a tunable diode laser absorption sensor for online monitoring of industrial gas total emissions based on ...

Published: 16 May 2016 in Optics Express

doi:

We report the first application of gas total emission using a DFB diode laser for gas concentration measurements combined with two LEDs for gas velocity measurements. In situ gas total emissions and particle density measurements in an industrial pipeline using simultaneous tunable diode laser absorption spectroscopy (TDLAS) and optical scintillation cross-correlation technique (OSCC) are presented. Velocity mean values obtained are 7.59 m/s (OSCC, standard deviation is 1.37 m/s) and 8.20 m/s (Pitot tube, standard deviation is 1.47 m/s) in a steel plant pipeline for comparison. Our experiments demonstrate that the combined system of TDLAS and OSCC provides a new versatile tool for accurate measurements of total gas emissions.

1 Reads | 0 Citations
2016
Apr
28
Published new article




Article

Development of a tunable diode laser absorption sensor for online monitoring of industrial gas total emissions based on ...

Published: 28 April 2016 by The Optical Society in Optics Express

doi: 10.1364/oe.24.00a943

We report the first application of gas total emission using a DFB diode laser for gas concentration measurements combined with two LEDs for gas velocity measurements. In situ gas total emissions and particle density measurements in an industrial pipeline using simultaneous tunable diode laser absorption spectroscopy (TDLAS) and optical scintillation cross-correlation technique (OSCC) are presented. Velocity mean values obtained are 7.59 m/s (OSCC, standard deviation is 1.37 m/s) and 8.20 m/s (Pitot tube, standard deviation is 1.47 m/s) in a steel plant pipeline for comparison. Our experiments demonstrate that the combined system of TDLAS and OSCC provides a new versatile tool for accurate measurements of total gas emissions.

0 Reads | 3 Citations
2015
Jul
01
Published new article




Article

Optimisation of laser linewidth and cavity alignment in off-axis cavity-enhanced absorption spectroscopy

Published: 01 July 2015 by Elsevier BV in Infrared Physics & Technology

doi: 10.1016/j.infrared.2015.03.011

1 Reads | 0 Citations
2014
Oct
13
Published new article




Article

Mid-infrared laser-spectroscopic sensing of chemical species

Published: 13 October 2014 by Elsevier BV in Journal of Advanced Research

doi: 10.1016/j.jare.2014.09.002

This letter reports on mid-infrared laser-based detection and analysis of chemical species. Emphasis is put on broadly tunable laser sources and sensitive detection schemes. Selected examples from our lab illustrate the performance and potential of such systems in various areas including environmental and medical sensing.

0 Reads | 6 Citations
2014
Aug
19
Published new article




Article

Broadly tunable mid-infrared VECSEL for multiple components hydrocarbon gas sensing

Published: 19 August 2014 by Springer Nature in Applied Physics B

doi: 10.1007/s00340-014-5911-1

A new sensing platform to simultaneously identify and quantify volatile C1 to C4 alkanes in multi-component gas mixtures is presented. This setup is based on an optically pumped, broadly tunable mid-infrared vertical-external-cavity surface-emitting laser (VECSEL) developed for gas detection. The lead-chalcogenide VECSEL is the key component of the presented optical sensor. The potential of the proposed sensing setup is illustrated by experimental absorption spectra obtained from various mixtures of volatile hydrocarbons and water vapor. The sensor has a sub-ppm limit of detection for each targeted alkane in a hydrocarbon gas mixture even in the presence of a high water vapor content.

5 Reads | 3 Citations
2014
Jan
01
Published new article




Article

Infrared detection of cocaine and street cocaine in saliva with a one-step extraction

Published: 01 January 2014 by Royal Society of Chemistry (RSC) in Analytical Methods

doi: 10.1039/c3ay41285g

We present a novel approach for the detection of cocaine in saliva using infrared attenuated total reflection spectroscopy combined with a simple one-step extraction. We demonstrate the performance of this technique with saliva collected from several test persons, spiked with cocaine and street cocaine after sampling. The high efficiency of the extraction yields a limit of detection (LOD) of ∼1 μg cocaine per ml of saliva. A further reduction of the LOD is easily achieved by pre-concentration enabling a limit of detection of a few 100 ng ml−1 of cocaine in saliva. The technique represents an important step towards a compact, easy-to-use, portable, quick and semi-quantitative screening device for on-road-side tests. The extraction method is also applicable to sample preparation for other optical sensor schemes.

1 Reads | 1 Citations
2014
Jan
01
Published new article






Cocaine detection in liquid using a fibered platform and a mid-infrared quantum cascade laser

Published: 01 January 2014 by The Optical Society in Advanced Photonics 2018 (BGPP, IPR, NP, NOMA, Sensors, Networks, SPPCom, SOF)

doi: 10.1364/sensors.2014.seth1c.2

A miniaturized, trace level sensor for cocaine is presented. A quantum cascade laser emitting at 1720 cm-1 is coupled to a fibred absorption flow-cell. A detection limit lower than 250 ng/mL (84 ppb) is reported.

0 Reads | 0 Citations
2013
Apr
10
Published new article




Article

Photothermal diffuse reflectance: a new tool for spectroscopic investigation of scattering samples

Published: 10 April 2013 by Springer Nature in Applied Physics B

doi: 10.1007/s00340-013-5437-y

A new method named photothermal diffuse reflectance (PTDR) is presented. This method combines the diffuse reflectance spectroscopy with the photothermal technique and is particularly suited for the investigation of strongly scattering samples. This method takes advantage of the high spectral selectivity and absorption of the mid-infrared region with the larger scattering cross section and high detector sensitivity available in the near-infrared. A model describing the PTDR method is proposed and supported with experimental results. The potential of the PTDR technique is illustrated by experimental signals obtained from various scattering media like polymers, liquids and powders.

4 Reads | 1 Citations
2013
Feb
02
Published new article




Article

Characterisation of the potential of frequency modulation and optical feedback locking for cavity-enhanced absorption sp...

Published: 02 February 2013 by Springer Nature in Applied Physics B

doi: 10.1007/s00340-013-5338-0

A combination of optical feedback self-locking of a continuous-wave distributed feedback diode laser to a V-shaped high finesse cavity, laser phase modulation at a frequency equal to the free spectral range of the V-cavity and detection of the transmitted laser beam at this high modulation frequency is described for the possible application in cavity-enhanced absorption spectroscopy. In order to estimate the noise level of an absorbance baseline, the triplet of frequency modulated light, i.e. the central laser frequency and the two sidebands, were transmitted through both the V-cavity in open air and a 1.5-cm long optical cell placed behind the cavity output mirror and filled with acetylene (C2H2) at low pressure. The performance of the setup was evaluated from the measured relative intensity noise on the cavity output (normalised by the bandwidth) and the frequency modulation absorption signals induced by C2H2 absorption in the 1.5-cm cell. From these data, we estimate that the noise-equivalent absorption sensitivity of 2.1 × 10−11 cm−1 Hz−1/2—by a factor of 11.7 above the shot-noise limit—can be achieved for C2H2 absorption spectra extracted from the heterodyne beat signals recorded at the transmission maxima intensity peaks of the successive TEM00 resonances.

4 Reads | 1 Citations
2012
Dec
16
Published new article






Characterisation of the potential of frequency modulation and optical feedback locking for cavity-enhanced absorption sp...

Published: 16 December 2012 by ArXiv

doi:

A combination of optical feedback self-locking of a continuous-wave distributed feedback diode laser to a V-shaped high finesse cavity, laser phase modulation at a frequency equal to the free spectral range of the V-cavity and detection of the transmitted laser beam at this high modulation frequency is described for possible application in cavity-enhanced absorption spectroscopy.In order to estimate an absorbance baseline noise of laser intensity and frequency modulated light triplet passed through the V-cavity in open air, a 1.5-cm long optical cell filled by C2H2 at low pressure was placed behind the cavity output mirror. The performance of the setup was evaluated from the experimental bandwidth normalised relative intensity noise on the cavity output and the frequency modulation absorption signals induced by C2H2 absorption in the 1.5-cm cell. From these data we estimate that the noise-equivalent absorption sensitivity of 2.1*10^-11 cm^-1 Hz^-1/2 by a factor of 11.7 above a shot-noise limit can be achieved for C2H2 absorption spectra extracted from the heterodyne beat signals recorded at the transmission maxima intensity peaks of the successive TEM00 resonances.

0 Reads | 0 Citations
2012
Mar
02
Published new article




Article

Chemical analysis of surgical smoke by infrared laser spectroscopy

Published: 02 March 2012 by Springer Nature in Applied Physics B

doi: 10.1007/s00340-012-4920-1

The chemical composition of surgical smoke, a gaseous by-product of some surgical devices—lasers, drills, vessel sealing devices—is of great interest due to the many toxic components that have been found to date. For the first time, surgical smoke samples collected during routine keyhole surgery were analyzed with infrared laser spectroscopy. Traces (ppm range) of methane, ethane, ethylene, carbon monoxide and sevoflurane were detected in the samples which consisted mostly of carbon dioxide and water vapor. Except for the anaesthetic sevoflurane, none of the compounds were present at dangerous concentrations. Negative effects on the health of operation room personnel can be excluded for many toxic compounds found in earlier studies, since their concentrations are below recommended exposure limits.

4 Reads | 3 Citations
2011
Nov
24
Published new article




Article

Infrared attenuated total reflection (IR-ATR) spectroscopy for detecting drugs in human saliva

Published: 24 November 2011 by Wiley in Drug Testing and Analysis

doi: 10.1002/dta.346

The consumption of drugs is of great concern worldwide. Various drug tests for humans have been developed but there is no compact and easy-to-use test device available yet for direct semi-quantitative drug testing in the field. We suggest using attenuated total reflection (ATR) infrared spectroscopy as a sensing method to analyze human saliva samples with respect to drugs. In this paper, we present ATR spectra in the infrared range between 2300 and 900 cm(-1) as a first step towards such a device. We emphasize the common drug cocaine and its metabolites and investigate the problems of spectral interferences of selected diluents, masking agents, common medication, and soft drinks. Furthermore, spectra of saliva samples are recorded and a time-dependent change of the spectral signatures after alcohol consumption is presented. To the best of our knowledge, it is the first time that not only spectra of the drug of interest (cocaine) dissolved in water and in saliva but also spectra of interfering compounds possibly present in the saliva sample of a tested subject are discussed. This paper presents the most appropriate spectral range for strong cocaine absorption (including its metabolites) and minimum interference by the investigated substances. This spectral window is found to be between 1800 and 1710 cm(-1). In addition, we demonstrate the feasibility to identify cocaine in saliva at a concentration of 0.020 mg/ml with IR-ATR-spectroscopy without any separation or extraction procedures. For example, this technique could also be applied for drug detection in waste water.

4 Reads | 8 Citations
2011
May
01
Published new article






Infrared spectroscopic determination of drugs in saliva

Published: 01 May 2011 by Institute of Electrical and Electronics Engineers (IEEE) in 2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference (CLEO EUROPE/EQEC)

doi: 10.1109/cleoe.2011.5943085

We present a new approach based on attenuated total reflection spectroscopy in the infrared using a very simple one-step extraction method. The method also enables the design of a microfluidic device that could perform the extraction by itself. First measurements were done with a Fourier-Transform-Infrared spectrometer. Saliva samples were taken from human test persons and then spiked with caffeine, COC and metabolites. Afterwards the drugs were extracted with an organic solvent immiscible with water. After the phase separation the drugs were measured in the organic solvent.

1 Reads | 0 Citations
2010
Oct
14
Published new article




Article

Automated broad tuning of difference frequency sources for spectroscopic studies

Published: 14 October 2010 by The Optical Society in Applied Optics

doi: 10.1364/ao.50.000a11

Transmission spectroscopy over large spectral ranges (>100 cm−1) generally requires a reference measurement to be taken separately from the sample scan. The ratio of the two measurements (i.e., the transmittance) is therefore susceptible to baseline changes that occur between the recording of the two spectra. The origins of relatively strong baseline changes (≫1%) of a difference-frequency-generation-based laser spectrometer (tuning range 2900–3144 cm−1, 150 μW average power) were investigated and a method for minimizing them by improving reproducibility and reducing measurement time is presented. The new method was tested for a gas mixture and the sensitivity for broad absorption features was determined as 5×10−3 minimum measurable absorbance for a total scan duration of 70 min.

1 Reads | 3 Citations
2010
Mar
26
Published new article




Article

Infrared Spectroscopy on Smoke Produced by Cauterization of Animal Tissue

Published: 26 March 2010 by MDPI in Sensors

doi: 10.3390/s100402694

In view of in vivo surgical smoke studies a difference-frequency-generation (DFG) laser spectrometer (spectral range 2900–3144 cm−1) and a Fourier-transform infrared (FTIR) spectrometer were employed for infrared absorption spectroscopy. The chemical composition of smoke produced in vitro with an electroknife by cauterization of different animal tissues in different atmospheres was investigated. Average concentrations derived are: water vapor (0.87%), methane (20 ppm), ethane (4.8 ppm), ethene (17 ppm), carbon monoxide (190 ppm), nitric oxide (25 ppm), nitrous oxide (40 ppm), ethyne (50 ppm) and hydrogen cyanide (25 ppm). No correlation between smoke composition and the atmosphere or the kind of cauterized tissue was found.

1 Reads | 8 Citations
2008
Jan
31
Published new article




Article

Special Issue: “6th International Conference on Tunable Diode Laser Spectroscopy”

Published: 31 January 2008 by Springer Nature in Applied Physics B

doi: 10.1007/s00340-008-2935-4

4 Reads | 2 Citations
2007
Dec
13
Published new article




Article

Trace gas monitoring with infrared laser-based detection schemes

Published: 13 December 2007 by Springer Nature in Applied Physics B

doi: 10.1007/s00340-007-2875-4

The success of laser-based trace gas sensing techniques crucially depends on the availability and performance of tunable laser sources combined with appropriate detection schemes. Besides near-infrared diode lasers, continuously tunable midinfrared quantum cascade lasers and nonlinear optical laser sources are preferentially employed today. Detection schemes are based on sensitive absorption measurements and comprise direct absorption in multi-pass cells as well as photoacoustic and cavity ringdown techniques in various configurations. We illustrate the performance of several systems implemented in our laboratory. These include time-resolved multicomponent traffic emission measurements with a mobile CO2-laser photoacoustic system, a diode-laser based cavity ringdown device for measurements of impurities in industrial process control, isotope ratio measurements with a difference frequency (DFG) laser source combined with balanced path length detection, detection of methylamines for breath analysis with both a near-IR diode laser and a DFG source, and finally, acetone measurements with a heatable multipass cell intended for vapor phase studies on doping agents in urine samples.

1 Reads | 51 Citations
2015
Jul
13
Conference participation




Markus Sigrist participated at conference 4th International Symposium on Sensor Science.

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