Skip to main content Accessibility help

We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.

Close cookie message
×
Hostname: page-component-cd9895bd7-8ctnn Total loading time: 0 Render date: 2024-12-28T01:37:27.736Z Has data issue: false hasContentIssue false

3 - Wavelength Modulation Spectroscopy with DFB Lasers

Published online by Cambridge University Press:  07 April 2021

George Stewart
George Stewart
Affiliation:
University of Strathclyde
Get access

Summary

Based on Fourier analysis, a theoretical description is given of the harmonics arising from current modulation of a DFB laser with its wavelength scanned through a gas absorption line. It is shown that each harmonic consists of a primary component from the wavelength modulation and two secondary components arising from the mixing of the intensity and wavelength modulations, with additional components if the laser light-current characteristic is non-linear. The importance of the lock-in detection phase is discussed and the need for calibration-free, consistent operation in the face of possible drift of laser parameters with time or with aging. Two methods are examined for extraction of gas parameters, one based on the effect of gas absorption on the laser intensity modulation, with correction factors applied at high modulation indices, and the other based on measurement of the second harmonic signal normalised through the first harmonic. It is shown that both methods can give similar sensitivities, but the harmonic ratio method is much superior in noise performance at the expense of increased complexity in signal processing and uncertainty if the laser parameters are prone to drift.

Keywords

Modulation spectroscopyFourier analysisfirst harmonicsecond harmonicharmonic ratiophase-sensitive detectionintensity modulationbackground modulationsignal-to-noisecalibration-free
Type
Chapter
Information
Laser and Fiber Optic Gas Absorption Spectroscopy , pp. 53 - 84
Publisher: Cambridge University Press
Print publication year: 2021

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Silver, J. A., Frequency-modulation spectroscopy for trace species detection: theory and comparison among experimental methods, Appl. Opt., 31, (6), 707–717, 1992.CrossRefGoogle ScholarPubMed
Supplee, J. M., Whittaker, E. A. and Lenth, W., Theoretical description of frequency modulation and wavelength modulation spectroscopy, Appl. Opt., 33, (27), 6294–6302, 1994.CrossRefGoogle ScholarPubMed
Avetisov, V. G. and Kauranen, P., High-resolution absorption measurements by use of two-tone frequency-modulation spectroscopy with diode lasers, Appl. Opt., 36, (18), 4043–4054, 1997.CrossRefGoogle ScholarPubMed
Goldenstein, C. S., Spearrin, R. M., Jeffries, J. B. and Hanson, R. K., Infrared laser-absorption sensing for combustion gases, Prog. Energy Combust. Sci., 60, 132–176, 2016.Google Scholar
Kluczynski, P. and Axner, O., Theoretical description based on Fourier analysis of wavelength-modulation spectrometry in terms of analytical and background signals, Appl. Opt., 38, (27), 5803–5815, 1999.Google Scholar
Kluczynski, P., Lindberg, A. M. and Axner, O., Characterization of background signals in wavelength modulation spectrometry in terms of a Fourier based formalism, Appl. Opt., 40, (6), 770–782, 2001.Google Scholar
Schilt, S., Thevenaz, L. and Robert, P., Wavelength modulation spectroscopy: combined frequency and intensity laser modulation, Appl. Opt., 42, (33), 6728–6738, 2003.CrossRefGoogle ScholarPubMed
Stewart, G., Johnstone, W., Bain, J. R. P., Ruxton, K. and Duffin, K., Recovery of absolute gas absorption line shapes using tuneable diode laser spectroscopy with wavelength modulation – part 1: theoretical analysis, IEEE J. Lightwave Technol., 29, (6), 811–821, 2011.Google Scholar
Bain, J. R. P., Johnstone, W. , Ruxton, K., et al., Recovery of absolute gas absorption line shapes using tunable diode laser spectroscopy with wavelength modulation – part 2: experimental investigation, IEEE J. Lightwave Technol., 29, (7), 987–996, 2011.Google Scholar
Duffin, K., McGettrick, A. J., Johnstone, W., Stewart, G. and Moodie, D. G., Tunable diode laser spectroscopy with wavelength modulation: a calibration-free approach to the recovery of absolute gas absorption line-shapes, IEEE J. Lightwave Technol., 25, (10), 3114–3131, 2007.Google Scholar
McGettrick, A. J., Duffin, K., Johnstone, W., Stewart, G. and Moodie, D. G., Tunable diode laser spectroscopy with wavelength modulation: a phasor decomposition method for calibration free measurements of gas concentration and pressure, IEEE J. Lightwave Technol., 26, (4), 432–440, 2008.Google Scholar
Johnstone, W., McGettrick, A. J., Duffin, K., Cheung, A. and Stewart, G., Tunable diode laser spectroscopy for industrial process applications: system characterisation in conventional and new approaches, IEEE Sens. J., 8, (7), 1079–1088, 2008.Google Scholar
Ruxton, K., Chakraborty, A. L., Johnstone, W., et al., Tunable diode laser spectroscopy with wavelength modulation: elimination of residual amplitude modulation in a phasor decomposition approach, Sens. Actuators, B: Chem., 150, (1), 367–375, 2010.Google Scholar
Upadhyay, A. and Chakraborty, A. L., Residual amplitude modulation method implemented at the phase quadrature frequency of a 1650nm laser diode for line shape recovery of methane, IEEE Sens. J., 15, (2), 1153–1160, 2015.Google Scholar
Benoy, T., Lengden, M., Stewart, G. and Johnstone, W., Recovery of absorption line-shapes with correction for the wavelength modulation characteristics of DFB lasers, IEEE Photon., 8, (3), 2016.Google Scholar
Chakraborty, A. L., Ruxton, K., Johnstone, W., Lengden, M. and Duffin, K., Elimination of residual amplitude modulation in tuneable diode laser wavelength modulation spectroscopy using an optical fiber delay line, Opt. Express, 17, (12), 9602–9607, 2009.Google Scholar
Chakraborty, A. L., Ruxton, K. and Johnstone, W., Influence of the wavelength-dependence of fiber couplers on the background signal in wavelength modulation spectroscopy with RAM nulling, Opt. Express, 18, (1), 267–280, 2010.Google Scholar
Chakraborty, A. L., Ruxton, K., Johnstone, W., Suppression of intensity modulation contributions to signals in second harmonic wavelength modulation spectroscopy, Opt. Lett., 35, (14), 2400–2402, 2010.CrossRefGoogle ScholarPubMed
Hobbs, P. C., Ultra-sensitive laser measurements without tears, Appl. Opt., 36, (4), 903–920, 1997.Google Scholar
Bain, J. R. P., Lengden, M., Stewart, G. and Johnstone, W., Recovery of absolute absorption line shapes in tunable diode laser spectroscopy using external amplitude modulation with balanced detection, IEEE Sens. J., 16, (3), 675–680, 2016.Google Scholar
Li, H., Rieker, G. B., Liu, X., Jeffries, J. B. and Hanson, R. K., Extension of wavelength modulation spectroscopy to large modulation depth for diode laser absorption measurements in high-pressure gases, Appl. Opt., 45, (5), 1052–1061, 2006.Google Scholar
Rieker, G. B., Jeffries, J. B. and Hanson, R. K., Calibration-free wavelength-modulation spectroscopy for measurements of gas temperature and concentration in harsh environments, Appl. Opt., 48, (29), 5546–5560, 2009.CrossRefGoogle ScholarPubMed
Sun, K., Chao, X., Sur, R., et al., Analysis of calibration-free wavelength-scanned wavelength modulation spectroscopy for practical gas sensing using tunable diode lasers, Meas. Sci. Technol., 24, (12), 125203–125214, 2013.Google Scholar
Goldenstein, C. S., Strand, C. L., Schultz, I. A., et al., Fitting of calibration-free scanned-wavelength-modulation spectroscopy spectra for determination of gas properties and absorption lineshapes, Appl. Opt., 53, (3), 356–367, 2014.Google Scholar
Goldenstein, C. S., Thesis: Wavelength-modulation spectroscopy for determination of gas properties in hostile environments, 2014. [Online]. Available: https://purl.stanford.edu/fg346yx4996 (accessed April 2020)Google Scholar
Benoy, T., Wilson, D., Lengden, M., et al., Measurement of CO2 concentration and temperature in an aero-engine exhaust plume using wavelength modulation spectroscopy, IEEE Sens. J., 17, (19), 6409–6417, 2017.Google Scholar
Upadhyay, A. and Chakraborty, A. L., Calibration-free 2f WMS with in situ real-time laser characterization and 2f RAM nulling, Opt. Lett., 40, (17), 4086–4089, 2015.Google Scholar
Upadhyay, A., Wilson, D., Lengden, M., et al., Calibration-free WMS using a cw-DFB-QCL, a VCSEL, and an edge-emitting DFB laser with in-situ real-time laser parameter characterization, IEEE Photon., 9, (2), 6801217, 2017.Google Scholar
Upadhyay, A., Lengden, M., Wilson, D., et al., A new RAM normalized 1f -WMS technique for the measurement of gas parameters in harsh environments and a comparison with 2f⁄1f, IEE Photon., 10, (6), 6804611, 2018.Google Scholar

Save book to Kindle

To save this book to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.

Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

Find out more about the Kindle Personal Document Service.

Available formats
×

Save book to Dropbox

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.

Available formats
×

Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

Available formats
×