Wavelength Modulated Cavity Enhanced Absorption Spectroscopy of Water in the 1.37 μm Region

Abstract

We describe the performance of a high-sensitivity wavelength modulated cavity enhanced infrared tunable diode laser absorption spectrometer for the detection of water vapor in the 1.37 μm region. The spectrometer can measure a fractional absorption of ∼10−5 for an absorption path length of a few kilometers. The instrument's sensitivity is more than sufficient to detect water isotopomers (H216O, H218O, HDO) at Martian atmospheric concentrations. The instrument is amenable to miniaturization, so a future compact, multiple-species version of the spectrometer will be highly suitable for in situ planetary exploration.