Comparison of the spectral excitation behavior of methane according to InP, GaSb, IC, and QC lasers as excitation source by sensor applications (original) (raw)
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Comparison of laser-based photoacoustic and optical detection of methane
Journal of Sensors and Sensor Systems
The measurement of low methane (CH 4) concentrations is a key objective for safety of industrial and public infrastructures and in environmental research. Laser spectroscopy is best suited for this purpose because it offers high sensitivity, selectivity, dynamic range, and a fast measurement rate. The physical basis of this technique is infrared absorption of molecular gases. Two detection schemes-direct absorption spectroscopy (DAS) and photoacoustic spectroscopy (PAS)-are compared at three wavelength regions in the near-infrared (NIR), mid-wavelength (MWIR), and long-wavelength (LWIR) infrared ranges. For each spectral range a suitable semiconductor laser is selected and used for both detection techniques: a diode laser (DL), an interband cascade laser (ICL), and a quantum cascade laser (QCL) for NIR, MWIR and LWIR, respectively. For DAS short absorption path lengths comparable to the cell dimensions of the photoacoustic cell for PAS are employed. We show that for DAS the lowest detection limit can be achieved in the MWIR range with noise-equivalent concentrations (NECs) below 10 ppb. Using PAS, lower detection limits and higher system stabilities can be reached compared to DAS, especially for long integration times. The lowest detection limit for PAS is obtained in the LWIR with a NEC of 7 ppb. The different DAS and PAS configurations are discussed with respect to potential applications.
A review of developments in near infrared methane detection based on tunable diode laser
Sensors and Actuators B: Chemical, 2012
Diode laser based absorption spectroscopy (DLAS) is widely used for gas detection in variety of applications across the energy, petrochemical and mining industries. Recent developments in near and mid infrared diode lasers have improved the sensitivity of gas measurement based on high resolution spectra of target species. The availability of near-infrared diodes that can operate at room temperature has expanded the application of spectroscopy technique in hand-held gas detection devices. DLAS in conjunction with optical fibres has also been applied for the distributed sensing and monitoring of various gases in real-time basis. This paper, after introducing methane characteristics and semiconductor diode lasers, comprehensively reviews development in spectroscopic methane sensing techniques in accordance with methane absorption lines in the near infrared spectrum.
Optics Letters, 1999
A quantum-cascade laser operating at a wavelength of 8.1 mm was used for high-sensitivity absorption spectroscopy of methane ͑CH 4 ͒. The laser frequency was continuously scanned with current over more than 3 cm 21 , and absorption spectra of the CH 4 n 4 P branch were recorded. The measured laser linewidth was 50 MHz. A CH 4 concentration of 15.6 parts in 10 6 ͑ppm͒ in 50 Torr of air was measured in a 43-cm path length with 60.5-ppm accuracy when the signal was averaged over 400 scans. The minimum detectable absorption in such direct absorption measurements is estimated to be 1.1 3 10 24 . The content of 13 CH 4 and CH 3 D species in a CH 4 sample was determined.
Applied Physics B, 2006
Spectral investigation around 6115 cm −1 for simultaneous detection of ammonia, methane and ethylene in gas samples is presented. Experimental data on the ν 2 + ν 3 + ν 4 combination band of ammonia are reported with a resolution of 1.5 GHz. A trace gas analyzer based on a resonant photoacoustic cell and an external cavity diode laser has been used for detection. A data fitting procedure has been developed in order to improve the system sensitivity and to limit the need of a reference cell. The selected spectral region allows a sensitivity of about 60 ppm for ammonia, 6 ppm for methane and 30 ppm for ethylene with 0.3 mW laser power. An application of simultaneous detection of such molecules in a mixture reproducing their typical abundances in real gas samples from biomass gasification is discussed. PACS 42.62.Fi; 42.55.Px; 82.80.Ch
Quantum-cascade laser photoacoustic detection of methane emitted from natural gas powered engines
Applied Physics B, 2012
In order to investigate the generation of greenhouse gases in sugarcane ethanol production chain, a comparative study of N 2 O emission in artificially fertilized soils and soils free from fertilizers was carried out. Photoacoustic spectroscopy using quantum cascade laser with an emission ranging from 7.71 to 7.88 lm and differential photoacoustic cell were applied to detect nitrous oxide (N 2 O), an important greenhouse gas emitted from soils cultivated with sugar cane. Owing to calibrate the experimental setup, an initial N 2 O concentration was diluted with pure nitrogen and detection limit of 50 ppbv was achieved. The proposed methodology was selective and sensitive enough to detect N 2 O from no fertilized and artificially fertilized soils. The measured N 2 O concentration ranged from ppmv to ppbv.
Infrared Dual-Gas CH4/C2H6Sensor Using Two Continuous-Wave Interband Cascade Lasers
IEEE Photonics Technology Letters, 2016
An infrared dual-gas sensor system for the simultaneous detection and monitoring of methane (CH4) and ethane (C2H6) at parts-per-billion by volume (ppbv) concentration levels was developed using two room temperature, distributed feedback (DFB) interband cascade lasers (ICLs) and two miniature multipass cells with an effective absorption length of 54.6 m. Laser direct absorption spectroscopy (LDAS) was used to detect CH4 utilizing the 3038.5 cm-1 absorption line, and second-harmonic wavelength modulation spectroscopy (2f-WMS) method was used to detect C2H6 using the 2996.88 cm-1 absorption line. The 1σ CH4 detection limit is ~ 2.7 ppbv with a 1 s averaging time and exhibits a minimum value of ~ 1.7 ppbv for a 9 s averaging time; the 1σ C2H6 detection limit is ~ 2.6 ppbv with a 3.4 s averaging time and shows an optimum averaging time of 65 s corresponding to a stability of ~ 0.36 ppbv. Using the dual-gas sensor system, 48 hours' monitoring of the two atmospheric gases was performed in the Greater Houston area, TX, USA.
Recent Advances in Trace Gas Detection Using Quantum and Interband Cascade Lasers
The Review of Laser Engineering, 2006
There is an increasing need in many chemical sensing applications ranging from environmental science to industrial process control as well as medical diagnostics for fast, sensitive, and selective trace gas detection based on laser spectroscopy. The recent availability of novel pulsed and continuous wave (cw) quantum and interband cascade distributed feedback (QC and IC DFB) lasers as mid-infrared spectroscopic sources addresses this need. A number of spectroscopic techniques have been demonstrated worldwide. For example, the authors have employed infrared DFB QC and IC lasers for the detection and quantification of trace gases and isotopic species in ambient air at ppmv, ppbv and even sub-ppbv levels by means of direct absorption, cavity enhanced, photoacoustic and wavelength modulation spectroscopy.
Sensors, 2016
A room-temperature continuous-wave (CW) quantum cascade laser (QCL)-based methane (CH 4) sensor operating in the mid-infrared near 8 µm was developed for continuous measurement of CH 4 concentrations in ambient air. The well-isolated absorption line (7F 2,4 Ð 8F 1,2) of the ν 4 fundamental band of CH 4 located at 1255.0004 cm´1 was used for optical measurement of CH 4 concentration by direct absorption in a White-type multipass cell with an effective path-length of 175 m. A 1σ (SNR = 1) detection limit of 33.3 ppb in 218 s was achieved with a measurement precision of 1.13%. The developed sensor was deployed in a campaign of measurements of time series CH 4 concentration on a site near a suburban traffic road in Dunkirk (France) from 9 to 22 January 2013. An episode of high CH 4 concentration of up to~3 ppm has been observed and analyzed with the help of meteorological parameters combined with back trajectory calculation using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model of NOAA.
Optics Express, 2016
A continuous-wave (CW) interband cascade laser (ICL) based mid-infrared sensor system was demonstrated for simultaneous detection of atmospheric methane (CH 4) and ethane (C 2 H 6). A 3.337 µm CW ICL with an emitting wavenumber range of 2996.0−3001.5 cm −1 was used to simultaneously target two absorption lines, C 2 H 6 at 2996.88 cm −1 and CH 4 at 2999.06 cm −1 , respectively. The sensor performance was first evaluated for single-gas detection by only targeting the absorption line of one gas species. Allan deviations of 11.2 parts per billion in volume (ppbv) for CH 4 and 1.86 ppbv for C 2 H 6 with an averaging time of 3.4 s were achieved for the detection of these two gases. Dual-gas detection was realized by using a long-term scan signal to target both CH 4 and C 2 H 6 lines. The Allan deviations increased slightly to 17.4 ppbv for CH 4 and 2.4 ppbv for C 2 H 6 with an averaging time of 4.6 s due to laser temperature and power drift caused by long-term wavelength scanning. Measurements for both indoor and outdoor concentration changes of CH 4 and C 2 H 6 were conducted. The reported single ICL based dual-gas sensor system has the advantages of reduced size and cost compared to two separate sensor systems.
Sensitive detection of methane at 3.3 μm using an integrating sphere and interband cascade laser
Proceedings of SPIE, 2016
Detection of methane at 3.3µm using a DFB Interband Cascade Laser and gold coated integrating sphere is performed. A 10cm diameter sphere with effective pathlength of 54.5cm was adapted for use as a gas cell. A comparison between this system and one using a 25cm pathlength single-pass gas cell is made using direct TDLS and methane concentrations between 0 and 1000 ppm. Initial investigations suggest a limit of detection of 1.0ppm for the integrating sphere and 2.2ppm for the single pass gas cell. The system has potential applications in challenging or industrial environments subject to high levels of vibration.