Wavelength modulation diode laser absorption spectroscopy for high-pressure gas sensing

A general model for 1f-normalized wavelength modulation absorption spectroscopy with nf detection (i.e., WMS-nf) is presented that considers the performance of injection-current-tuned diode lasers and the reflective interference produced by other optical components on the line-of-sight (LOS) transmission intensity. This model explores the optimization of sensitive detection of optical absorption by species with structured spectra at elevated pressures. Predictions have been validated by comparison with measurements of the 1f-normalized WMS-nf (for n = 2–6) lineshape of the R(11) transition in the 1st overtone band of CO near 2.3 μm at four different pressures ranging from 5 to 20 atm, all at room temperature. The CO mole fractions measured by 1f-normalized WMS-2f, 3f, and 4f techniques agree with calibrated mixtures within 2.0 %. At conditions where absorption features are significantly broadened and large modulation depths are required, uncertainties in the WMS background signals due to reflective interference in the optical path can produce significant error in gas mole fraction measurements by 1f-normalized WMS-2f. However, such potential errors can be greatly reduced by using the higher harmonics, i.e., 1f-normalized WMS-nf with n > 2. In addition, less interference from pressure-broadened neighboring transitions has been observed for WMS with higher harmonics than for WMS-2f.

[1]  Ronald K. Hanson,et al.  High-pressure measurements of CO2 absorption near 2.7 μm: Line mixing and finite duration collision effects , 2010 .

[2]  D. Labrie,et al.  Second-harmonic detection with tunable diode lasers — Comparison of experiment and theory , 1981 .

[3]  Ove Axner,et al.  A general non-complex analytical expression for the nth Fourier component of a wavelength-modulated Lorentzian lineshape function , 2001 .

[4]  T. Aizawa.  Diode-Laser Wavelength-Modulation Absorption Spectroscopy for Quantitative in situ Measurements of Temperature and OH Radical Concentration in Combustion Gases. , 2001, Applied optics.

[5]  Christopher R. Webster,et al.  Brewster-plate spoiler: a novel method for reducing the amplitude of interference fringes that limit tunable-laser absorption sensitivities , 1985 .

[6]  Jürgen Wolfrum,et al.  Lasers in combustion: From basic theory to practical devices , 1998 .

[7]  M. Allen,et al.  Diode laser absorption sensors for gas-dynamic and combustion flows. , 1998, Measurement science & technology.

[8]  Jörgen Gustafsson,et al.  Wavelength modulation absorption spectrometry — an extensive scrutiny of the generation of signals , 2001 .

[9]  O. Axner,et al.  Background signals in wavelength-modulation spectrometry with frequency-doubled diode-laser light. I. Theory. , 2001, Applied optics.

[10]  Volker Ebert,et al.  Digital, phase-sensitive detection for in situ diode-laser spectroscopy under rapidly changing transmission conditions , 2002 .

[11]  P. Werle.  Spectroscopic trace gas analysis using semiconductor diode lasers , 1996 .

[12]  Jonathan Tennyson,et al.  HITEMP, the high-temperature molecular spectroscopic database , 2010 .

[13]  Ronald K. Hanson,et al.  Wavelength-modulation-spectroscopy for real-time, in situ NO detection in combustion gases with a 5.2 μm quantum-cascade laser , 2012 .

[14]  Daniel T. Cassidy,et al.  Atmospheric pressure monitoring of trace gases using tunable diode lasers. , 1982, Applied optics.

[15]  Hejie Li,et al.  Extension of wavelength-modulation spectroscopy to large modulation depth for diode laser absorption measurements in high-pressure gases. , 2006, Applied optics.

[16]  O. Axner,et al.  Background Signals in Wavelength-Modulation Spectrometry by use of Frequency-Doubled Diode-Laser Light. II. Experiment. , 2001, Applied optics.

[17]  Peter Werle,et al.  A review of recent advances in semiconductor laser based gas monitors , 1998 .

[18]  R. Hanson,et al.  In situ combustion measurements of CO with diode-laser absorption near 2.3 microm. , 2000, Applied optics.

[19]  O. Axner,et al.  Characterization of 2f-, 4f-, and 6f-background signals in wavelength modulation diode laser absorption spectrometry in graphite furnaces , 2003 .

[20]  B K Garside,et al.  High sensitivity pollution detection employing tunable diode lasers. , 1978, Applied optics.

[21]  Jonathan T. C. Liu,et al.  Large-modulation-depth 2f spectroscopy with diode lasers for rapid temperature and species measurements in gases with blended and broadened spectra. , 2004, Applied optics.

[22]  Ronald K. Hanson,et al.  Measurements of high-pressure CO2 absorption near 2.0 μm and  implications on tunable diode laser sensor design , 2009 .

[23]  Ronald K. Hanson,et al.  Applications of quantitative laser sensors to kinetics, propulsion and practical energy systems , 2011 .

[24]  Jörgen Gustafsson,et al.  ‘Intelligent’ triggering methodology for improved detectability of wavelength modulation diode laser absorption spectrometry applied to window-equipped graphite furnaces , 2003 .

[25]  Ronald K. Hanson,et al.  Laser diode wavelength-modulation spectroscopy for simultaneous measurement of temperature, pressure, and velocity in shock-heated oxygen flows. , 1993, Applied optics.

[26]  O. Axner,et al.  Theoretical description based on Fourier analysis of wavelength-modulation spectrometry in terms of analytical and background signals. , 1999, Applied optics.

[27]  R. Hanson,et al.  Calibration-free wavelength-modulation spectroscopy for measurements of gas temperature and concentration in harsh environments. , 2009, Applied optics.

[28]  Rolf Arndt,et al.  Analytical Line Shapes for Lorentzian Signals Broadened by Modulation , 1965 .

[29]  J. A. Silver,et al.  Frequency-modulation spectroscopy for trace species detection: theory and comparison among experimental methods. , 1992, Applied optics.

[30]  Ronald K. Hanson,et al.  Measurements of near-IR water vapor absorption at high pressure and temperature , 2007 .

[31]  D. Cassidy,et al.  Trace gas detection with short-external-cavity InGaAsP diode laser transmitter modules operating at 1.58 microm. , 1988, Applied optics.

[32]  Ronald K. Hanson,et al.  Absorption sensor for CO in combustion gases using 2.3 µm tunable diode lasers , 2009 .