Recovery of absorption line shapes with correction for the wavelength modulation characteristics of DFB lasers

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Abstract

Tunable diode laser spectroscopy combined with wavelength modulation spectroscopy (WMS) is an important technique for non-invasive measurements of gas parameters such as pressure, concentration and temperature in high noise, harsh environments. A variety of laser types are used for these applications and the modulation characteristics can have significant effects on line shape recovery. Here we identify important characteristics of distributed feedback (DFB) lasers that need to be taken into account in the context of WMS and illustrate the effects with a 2μm wavelength, multi quantum well DFB laser used for CO2 detection. The modulation response of the laser is measured and we demonstrate how the phasor decomposition method (PDM) may be used to obtain accurate line shapes from first harmonic WMS signals by correcting for phase variation across the laser’s low frequency current sweep. We also demonstrate how the PDM approach can be improved by removing the need to pre-set the orientation of the lock-in axis, to isolate the residual amplitude modulation(RAM)component, making it more suitable for field applications.
Original languageEnglish
Article number1501717
Number of pages16
JournalIEEE Photonics Journal
Volume8
Issue number3
DOIs
Publication statusPublished - 4 May 2016

Fingerprint

Distributed feedback lasers
distributed feedback lasers
line shape
recovery
Modulation
modulation
Recovery
Wavelength
wavelengths
Spectroscopy
Lasers
spectroscopy
lasers
Decomposition
decomposition
Laser spectroscopy
Amplitude modulation
quantum well lasers
laser spectroscopy
Semiconductor quantum wells

Keywords

  • diode laser spectroscopy
  • absorption line shape recovery
  • laser modulation
  • wavelength modulation spectroscopy
  • optical gas sensors

Cite this

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title = "Recovery of absorption line shapes with correction for the wavelength modulation characteristics of DFB lasers",
abstract = "Tunable diode laser spectroscopy combined with wavelength modulation spectroscopy (WMS) is an important technique for non-invasive measurements of gas parameters such as pressure, concentration and temperature in high noise, harsh environments. A variety of laser types are used for these applications and the modulation characteristics can have significant effects on line shape recovery. Here we identify important characteristics of distributed feedback (DFB) lasers that need to be taken into account in the context of WMS and illustrate the effects with a 2μm wavelength, multi quantum well DFB laser used for CO2 detection. The modulation response of the laser is measured and we demonstrate how the phasor decomposition method (PDM) may be used to obtain accurate line shapes from first harmonic WMS signals by correcting for phase variation across the laser’s low frequency current sweep. We also demonstrate how the PDM approach can be improved by removing the need to pre-set the orientation of the lock-in axis, to isolate the residual amplitude modulation(RAM)component, making it more suitable for field applications.",
keywords = "diode laser spectroscopy, absorption line shape recovery, laser modulation, wavelength modulation spectroscopy, optical gas sensors",
author = "Thomas Benoy and Michael Lengden and George Stewart and Walter Johnstone",
year = "2016",
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language = "English",
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T1 - Recovery of absorption line shapes with correction for the wavelength modulation characteristics of DFB lasers

AU - Benoy, Thomas

AU - Lengden, Michael

AU - Stewart, George

AU - Johnstone, Walter

PY - 2016/5/4

Y1 - 2016/5/4

N2 - Tunable diode laser spectroscopy combined with wavelength modulation spectroscopy (WMS) is an important technique for non-invasive measurements of gas parameters such as pressure, concentration and temperature in high noise, harsh environments. A variety of laser types are used for these applications and the modulation characteristics can have significant effects on line shape recovery. Here we identify important characteristics of distributed feedback (DFB) lasers that need to be taken into account in the context of WMS and illustrate the effects with a 2μm wavelength, multi quantum well DFB laser used for CO2 detection. The modulation response of the laser is measured and we demonstrate how the phasor decomposition method (PDM) may be used to obtain accurate line shapes from first harmonic WMS signals by correcting for phase variation across the laser’s low frequency current sweep. We also demonstrate how the PDM approach can be improved by removing the need to pre-set the orientation of the lock-in axis, to isolate the residual amplitude modulation(RAM)component, making it more suitable for field applications.

AB - Tunable diode laser spectroscopy combined with wavelength modulation spectroscopy (WMS) is an important technique for non-invasive measurements of gas parameters such as pressure, concentration and temperature in high noise, harsh environments. A variety of laser types are used for these applications and the modulation characteristics can have significant effects on line shape recovery. Here we identify important characteristics of distributed feedback (DFB) lasers that need to be taken into account in the context of WMS and illustrate the effects with a 2μm wavelength, multi quantum well DFB laser used for CO2 detection. The modulation response of the laser is measured and we demonstrate how the phasor decomposition method (PDM) may be used to obtain accurate line shapes from first harmonic WMS signals by correcting for phase variation across the laser’s low frequency current sweep. We also demonstrate how the PDM approach can be improved by removing the need to pre-set the orientation of the lock-in axis, to isolate the residual amplitude modulation(RAM)component, making it more suitable for field applications.

KW - diode laser spectroscopy

KW - absorption line shape recovery

KW - laser modulation

KW - wavelength modulation spectroscopy

KW - optical gas sensors

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