Abstract

Recent advances in room-temperature visible diode lasers and ultrasensitive detection techniques have been exploited to create a highly sensitive tunable diode laser absorption technique for in situ monitoring of NO₂ in the lower troposphere. High sensitivity to NO₂ is achieved by probing the visible absorption band of NO₂ with an AlGaInP diode laser at 640 or 670 nm combined with a balanced ratiometric electronic detection technique. We have demonstrated a sensitivity of 3.5 × 10¹⁰ cm⁻³ for neat NO₂ in a 1-m path at 640 nm and have estimated a sensitivity for ambient operation of 5 ppbv m (10 ppbv m at 670 nm), where ppbvm is parts in 10⁹ by volume per meter of absorption path length, from measured pressure-broadening coefficients.

© 1996 Optical Society of America

Tunable diode-laser absorption measurements of NO₂ near 670 and 395 nm

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