Tunable diode and fibre laser spectroscopy in the near-IR for measurement of gas parameters

G. Stewart, W. Johnstone, N. Arsad, K. Duffin

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5 Citations (Scopus)

Abstract

There has been much research performed in recent years on tunable diode laser spectroscopy for detection of gases such as methane, carbon dioxide, acetylene, etc., which possess near-IR absorption lines. To attain adequate sensitivity with weak near-IR lines, wavelength modulation spectroscopy with phase-sensitive detection is normally employed. However injection current modulation of diode lasers produces both wavelength and amplitude modulation, with a phase shift dependent on the modulation frequency. This results in residual amplitude modulation on the output and in distortion of the harmonic signals derived from the absorption line. These are important issues for calibration and where it is desired to accurately recover the line-shape function in order to make simultaneous measurements of gas concentration, pressure or temperature in industrial applications. Here we discuss how calibration-free measurements may be obtained with diode lasers and explore the implications for fibre laser based systems for spectroscopy which conventionally employ thermal or piezoelectric tuning of the wavelength. In particular, we consider modulation techniques which may be applied to ring fibre lasers which use un-pumped erbium fibre as a saturable absorber to prevent mode-hopping or to DFB fibre lasers which use a short cavity with a Bragg grating to ensure single mode operation.

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Laser Spectroscopy
Tunable Laser
Laser spectroscopy
Diode Laser
Fiber Laser
Fiber lasers
laser spectroscopy
fiber lasers
Semiconductor lasers
Amplitude modulation
Gases
semiconductor lasers
Modulation
modulation
Wavelength
Amplitude Modulation
Line
gases
Erbium
Spectroscopy

Keywords

  • fibre sensors
  • fibre lasers
  • DFB lasers
  • diode laser spectroscopy
  • wavelength modulation spectroscopy
  • gas sensors

Cite this

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title = "Tunable diode and fibre laser spectroscopy in the near-IR for measurement of gas parameters",
abstract = "There has been much research performed in recent years on tunable diode laser spectroscopy for detection of gases such as methane, carbon dioxide, acetylene, etc., which possess near-IR absorption lines. To attain adequate sensitivity with weak near-IR lines, wavelength modulation spectroscopy with phase-sensitive detection is normally employed. However injection current modulation of diode lasers produces both wavelength and amplitude modulation, with a phase shift dependent on the modulation frequency. This results in residual amplitude modulation on the output and in distortion of the harmonic signals derived from the absorption line. These are important issues for calibration and where it is desired to accurately recover the line-shape function in order to make simultaneous measurements of gas concentration, pressure or temperature in industrial applications. Here we discuss how calibration-free measurements may be obtained with diode lasers and explore the implications for fibre laser based systems for spectroscopy which conventionally employ thermal or piezoelectric tuning of the wavelength. In particular, we consider modulation techniques which may be applied to ring fibre lasers which use un-pumped erbium fibre as a saturable absorber to prevent mode-hopping or to DFB fibre lasers which use a short cavity with a Bragg grating to ensure single mode operation.",
keywords = "fibre sensors, fibre lasers, DFB lasers, diode laser spectroscopy, wavelength modulation spectroscopy, gas sensors",
author = "G. Stewart and W. Johnstone and N. Arsad and K. Duffin",
year = "2008",
doi = "10.1117/12.779976",
language = "English",
volume = "7003",
pages = "700319",
journal = "Proceedings of SPIE",
issn = "0277-786X",

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TY - JOUR

T1 - Tunable diode and fibre laser spectroscopy in the near-IR for measurement of gas parameters

AU - Stewart, G.

AU - Johnstone, W.

AU - Arsad, N.

AU - Duffin, K.

PY - 2008

Y1 - 2008

N2 - There has been much research performed in recent years on tunable diode laser spectroscopy for detection of gases such as methane, carbon dioxide, acetylene, etc., which possess near-IR absorption lines. To attain adequate sensitivity with weak near-IR lines, wavelength modulation spectroscopy with phase-sensitive detection is normally employed. However injection current modulation of diode lasers produces both wavelength and amplitude modulation, with a phase shift dependent on the modulation frequency. This results in residual amplitude modulation on the output and in distortion of the harmonic signals derived from the absorption line. These are important issues for calibration and where it is desired to accurately recover the line-shape function in order to make simultaneous measurements of gas concentration, pressure or temperature in industrial applications. Here we discuss how calibration-free measurements may be obtained with diode lasers and explore the implications for fibre laser based systems for spectroscopy which conventionally employ thermal or piezoelectric tuning of the wavelength. In particular, we consider modulation techniques which may be applied to ring fibre lasers which use un-pumped erbium fibre as a saturable absorber to prevent mode-hopping or to DFB fibre lasers which use a short cavity with a Bragg grating to ensure single mode operation.

AB - There has been much research performed in recent years on tunable diode laser spectroscopy for detection of gases such as methane, carbon dioxide, acetylene, etc., which possess near-IR absorption lines. To attain adequate sensitivity with weak near-IR lines, wavelength modulation spectroscopy with phase-sensitive detection is normally employed. However injection current modulation of diode lasers produces both wavelength and amplitude modulation, with a phase shift dependent on the modulation frequency. This results in residual amplitude modulation on the output and in distortion of the harmonic signals derived from the absorption line. These are important issues for calibration and where it is desired to accurately recover the line-shape function in order to make simultaneous measurements of gas concentration, pressure or temperature in industrial applications. Here we discuss how calibration-free measurements may be obtained with diode lasers and explore the implications for fibre laser based systems for spectroscopy which conventionally employ thermal or piezoelectric tuning of the wavelength. In particular, we consider modulation techniques which may be applied to ring fibre lasers which use un-pumped erbium fibre as a saturable absorber to prevent mode-hopping or to DFB fibre lasers which use a short cavity with a Bragg grating to ensure single mode operation.

KW - fibre sensors

KW - fibre lasers

KW - DFB lasers

KW - diode laser spectroscopy

KW - wavelength modulation spectroscopy

KW - gas sensors

UR - http://spiedl.aip.org/dbt/dbt.jsp?KEY=PSISDG&Volume=7003&Issue=1#Chemical%20and%20Environmental%20Sensing%20I

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DO - 10.1117/12.779976

M3 - Article

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SP - 700319

JO - Proceedings of SPIE

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SN - 0277-786X

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