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.
| Original language | English |
|---|---|
| Title of host publication | Proceedings of SPIE - The International Society for Optical Engineering |
| Volume | 7003 |
| DOIs | |
| Publication status | Published - 2008 |
| Externally published | Yes |
| Event | Optical Sensors 2008 - Strasbourg Duration: 7 Apr 2008 → 10 Apr 2008 |
Other
| Other | Optical Sensors 2008 |
|---|---|
| City | Strasbourg |
| Period | 7/4/08 → 10/4/08 |
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Keywords
- DFB lasers
- Diode laser spectroscopy
- Fibre lasers
- Fibre sensors
- Gas sensors
- Wavelength modulation spectroscopy
ASJC Scopus subject areas
- Electrical and Electronic Engineering
- Condensed Matter Physics
Cite this
Tunable diode and fibre laser spectroscopy in the near-IR for measurement of gas parameters. / Stewart, George; Johnstone, Walter; Arsad, Norhana; Duffin, Kevin.
Proceedings of SPIE - The International Society for Optical Engineering. Vol. 7003 2008. 700319.Research output: Chapter in Book/Report/Conference proceeding › Conference contribution
}
TY - GEN
T1 - Tunable diode and fibre laser spectroscopy in the near-IR for measurement of gas parameters
AU - Stewart, George
AU - Johnstone, Walter
AU - Arsad, Norhana
AU - Duffin, Kevin
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 - DFB lasers
KW - Diode laser spectroscopy
KW - Fibre lasers
KW - Fibre sensors
KW - Gas sensors
KW - Wavelength modulation spectroscopy
UR - http://www.scopus.com/inward/record.url?scp=50249133051&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=50249133051&partnerID=8YFLogxK
U2 - 10.1117/12.779976
DO - 10.1117/12.779976
M3 - Conference contribution
SN - 9780819472014
VL - 7003
BT - Proceedings of SPIE - The International Society for Optical Engineering
ER -