Abstract.
A dual-beam laser absorption spectrometer with balanced detection for high sensitivity detection of oxygen via the A-band at 760 nm is described. The 2×2 vertical-cavity surface-emitting laser arrays used for this set-up are characterized by their wavelength tuning behavior with temperature and current, amplitude modulation, side-mode suppression ratio and polarization contrast. The spectrometer performance is determined over time periods of up to 10 h using the variation in the differential absorption between two beam paths. With the R11R11 line at STP, 670 μW laser power and 200 mm-long absorption cells, we realized an excellent linearity (R=0.9999) and over a 5-min interval a record sensitivity for VCSEL-based spectrometers of 35 ppmV, corresponding to an optical density (O.D.) of 7×10-7. For this specific set-up, this sensitivity is only a factor of 2.7 above the shot noise limit, giving us a normalized detection limit of 7.6 ppmV·m·. Over a 10-h interval we achieved a standard deviation of 65 ppmV.
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Received: 26 July 2000 / Revised version: 1 November 2000 / Published online: 6 December 2000
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Vogel, P., Ebert, V. Near shot noise detection of oxygen in the A-band with vertical-cavity surface-emitting lasers . Appl Phys B 72, 127–135 (2001). https://doi.org/10.1007/s003400000516
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DOI: https://doi.org/10.1007/s003400000516