Oxygen measurements at high pressures with vertical cavity surface-emitting lasers |
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Authors: | J Wang ST Sanders JB Jeffries RK Hanson |
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Institution: | (1) High Temperature Gasdynamics Laboratory, Department of Mechanical Engineering, Stanford University, Stanford, California 94305-3032, USA, US |
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Abstract: | Measurements of oxygen concentration at high pressures (to 10.9 bar) were made using diode-laser absorption of oxygen A-band
transitions near 760 nm. The wide current-tuning frequency range (>30 cm-1) of vertical cavity surface-emitting lasers (VCSELs) was exploited to enable the first scanned-wavelength demonstration of
diode-laser absorption at high pressures; this strategy is more robust than fixed-wavelength strategies, particularly in hostile
environments. The wide tuning range and rapid frequency response of the current tuning were further exploited to demonstrate
wavelength-modulation absorption spectroscopy in a high-pressure environment. The minimum detectable absorbance demonstrated,
∼1×10-4, corresponds to ∼800 ppm-m oxygen detectivity at room temperature and is limited by etalon noise. The rapid- and wide-frequency
tunability of VCSELs should significantly expand the application domain of absorption-based sensors limited in the past by
the small current-tuning frequency range (typically <2 cm-1) of conventional edge-emitting diode lasers.
Received: 26 July 2000 / Revised version: 2 January 2001 / Published online: 20 April 2001 |
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Keywords: | PACS: 07 07 Df 42 62 Fi 42 55 Px |
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