Wavelength Modulation Spectroscopy
359
are now possible with the mid-infrared region becoming more accessible than ever
before. The analytical framework of WMS is now very well developed and takes
into account the modulation behaviour of edge-emitting lasers, VCSELs and QCLs.
The calibration-free algorithms have made a telling contribution and are expected
to be used more widely as more applied research is reported. More work is likely
to emerge from the combination of these techniques and new types of QCLs that
exhibit exotic modulation behaviour. Recent research has shown zero-background
trace gas sensing using QCLs that exhibit pure IM [64]. QCLs with integrated heaters
have been demonstrated that can be operated in a pure IM mode as well as in a pure
IM/FM mode of operation [65]. It would be very interesting to see how the WMS
techniques discussed in this chapter perform on such new types of lasers.
References
1. O. Witzel, A. Klein, C. Meffert, S. Wagner, S. Kaiser, C. Schulz, V. Ebert, VCSEL-based, highspeed, in situ TDLAS for in-cylinder water vapor measurements in IC engines. Opt. Express,
21, 19951–19965 (2013) (Optical Society of America)
2. X. Chao, J.B. Jeffries, R.K. Hanson, Wavelength modulation spectroscopy for real-time, in situ
NO detection in combustion gases with a 5.2 µ m quantum cascade laser. Appl. Phys. B 106,
987–997 (2012)
3. A. Hangauer, J. Chen, R. Strzoda, M. Fleischer, M.-C. Amann, Performance of a fire detector
based on a compact laser spectroscopic carbon monoxide sensor. Opt. Express, 22,13680–
13690 (2014) (Optical Society of America)
4. L.C. Philippe R.K. Hanson, Laser diode wavelength-modulation spectroscopy for simultaneous
measurement of temperature, pressure, and velocity in shock-heated oxygen flows. Appl. Opt.
32, 6090–6103 (1993) (Optical Society of America)
5. M.E. Webber, R. Claps, F.V. Englich, F.K. Tittel, J.B. Jeffries, R K. Hanson, Measurements
of NH 3 and CO 2 with distributed-feedback diode lasers near 2.0 µ m in bioreactor vent gases.
Appl. Opt., 40, 4395–4403 (2001) (Optical Society of America)
6. G.B. Rieker, J.B. Jeffries, R.K. Hanson, Calibration-free wavelength modulation spectroscopy
for measurements of gas temperature and concentration in harsh environments. Appl. Opt. 48,
5546–5560 (2009) (Optical Society of America)
7. A. Farooq, J.B. Jeffries, R.K. Hanson, In situ combustion measurements of H 2 O and temperature near 2.5 µm using tunable diode laser absorption. Measure. Sci. Technol. 19, 075604
(2008)
8. J.J. Girard, R.M. Spearrin, C.S. Goldenstein, R.K. Hanson, Compact optical probe for flame
temperature and carbon dioxide using interband cascade laser absorption near 4.2 µm. Combust.
Flame 178, 158–167 (2017)
9. D.J. Miller, K.Sun, L.Tao, M.A. Khan, M.A. Zondlo, Open-path, quantum cascade-laser-based
sensor for high-resolution atmospheric ammonia measurements. Atmos. Measure. Tech. 7,
81–93 (2014) (Copernicus GmbH)
10. A.Roy, N.K. Sharma, A.L. Chakraborty, A. Upadhyay, Measurement of atmospheric carbon
dioxide and water vapor in built-up urban areas in the Gandhinagar-Ahmedabad region in
India using a portable tunable diode laser spectroscopy system,. Appl. Opt. 56, H57–H66
(2017) (Optical Society of America)
11. A. Khan, D. Schaefer, L. Tao, D.J. Miller, K. Sun, M.A. Zondlo, W.A. Harrison, B. Roscoe,
D.J. Lary, Low power greenhouse gas sensors for unmanned aerial vehicles. Remote Sens. 4,
1355–1368 (2012) (Number 5 Molecular Diversity Preservation International)
359
are now possible with the mid-infrared region becoming more accessible than ever
before. The analytical framework of WMS is now very well developed and takes
into account the modulation behaviour of edge-emitting lasers, VCSELs and QCLs.
The calibration-free algorithms have made a telling contribution and are expected
to be used more widely as more applied research is reported. More work is likely
to emerge from the combination of these techniques and new types of QCLs that
exhibit exotic modulation behaviour. Recent research has shown zero-background
trace gas sensing using QCLs that exhibit pure IM [64]. QCLs with integrated heaters
have been demonstrated that can be operated in a pure IM mode as well as in a pure
IM/FM mode of operation [65]. It would be very interesting to see how the WMS
techniques discussed in this chapter perform on such new types of lasers.
References
1. O. Witzel, A. Klein, C. Meffert, S. Wagner, S. Kaiser, C. Schulz, V. Ebert, VCSEL-based, highspeed, in situ TDLAS for in-cylinder water vapor measurements in IC engines. Opt. Express,
21, 19951–19965 (2013) (Optical Society of America)
2. X. Chao, J.B. Jeffries, R.K. Hanson, Wavelength modulation spectroscopy for real-time, in situ
NO detection in combustion gases with a 5.2 µ m quantum cascade laser. Appl. Phys. B 106,
987–997 (2012)
3. A. Hangauer, J. Chen, R. Strzoda, M. Fleischer, M.-C. Amann, Performance of a fire detector
based on a compact laser spectroscopic carbon monoxide sensor. Opt. Express, 22,13680–
13690 (2014) (Optical Society of America)
4. L.C. Philippe R.K. Hanson, Laser diode wavelength-modulation spectroscopy for simultaneous
measurement of temperature, pressure, and velocity in shock-heated oxygen flows. Appl. Opt.
32, 6090–6103 (1993) (Optical Society of America)
5. M.E. Webber, R. Claps, F.V. Englich, F.K. Tittel, J.B. Jeffries, R K. Hanson, Measurements
of NH 3 and CO 2 with distributed-feedback diode lasers near 2.0 µ m in bioreactor vent gases.
Appl. Opt., 40, 4395–4403 (2001) (Optical Society of America)
6. G.B. Rieker, J.B. Jeffries, R.K. Hanson, Calibration-free wavelength modulation spectroscopy
for measurements of gas temperature and concentration in harsh environments. Appl. Opt. 48,
5546–5560 (2009) (Optical Society of America)
7. A. Farooq, J.B. Jeffries, R.K. Hanson, In situ combustion measurements of H 2 O and temperature near 2.5 µm using tunable diode laser absorption. Measure. Sci. Technol. 19, 075604
(2008)
8. J.J. Girard, R.M. Spearrin, C.S. Goldenstein, R.K. Hanson, Compact optical probe for flame
temperature and carbon dioxide using interband cascade laser absorption near 4.2 µm. Combust.
Flame 178, 158–167 (2017)
9. D.J. Miller, K.Sun, L.Tao, M.A. Khan, M.A. Zondlo, Open-path, quantum cascade-laser-based
sensor for high-resolution atmospheric ammonia measurements. Atmos. Measure. Tech. 7,
81–93 (2014) (Copernicus GmbH)
10. A.Roy, N.K. Sharma, A.L. Chakraborty, A. Upadhyay, Measurement of atmospheric carbon
dioxide and water vapor in built-up urban areas in the Gandhinagar-Ahmedabad region in
India using a portable tunable diode laser spectroscopy system,. Appl. Opt. 56, H57–H66
(2017) (Optical Society of America)
11. A. Khan, D. Schaefer, L. Tao, D.J. Miller, K. Sun, M.A. Zondlo, W.A. Harrison, B. Roscoe,
D.J. Lary, Low power greenhouse gas sensors for unmanned aerial vehicles. Remote Sens. 4,
1355–1368 (2012) (Number 5 Molecular Diversity Preservation International)