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V. Ebert, T. Fernholz, P. Vogel

Sensitive Extractive Detection of Oxygen and Methane with Near Infrared Diode Lasers

A highly linear (R = 0.9999) dual beam laser absorption spectrometer is described with balanced detection and 200 mm absorption path for sensitive detection of O₂ via R11 R11-line in the A-band at 760 nm and CH₄ via the R3-transition of 2ν₃-band. Various laser types are compared with regard to their performance. A record sensitivity for Vertical-Cavity-Laser based spectrometers of 35 ppmV O₂ over a 5 min interval, corresponding to an OD of 7 × 10⁻⁷ is reported, which is only a factor of 3 above the shot noise limit. The normalized detection limit is 7.6 ppmV · m · mW^1/2 · s^1/2. Using a Distributed-Feedback-Diode-Laser in a new external cavity setup at 1.65 μm a detectivity of 600 ppb · m CH₄ is achieved.

tm – Technisches Messen, Oldenbourg Wissenschaftsverlag

Print ISSN: 0171-8096
Volume: 68, 10/2001
Pages: 439

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