Phase-shift off-axis cavity-enhanced absorption detector of nitrogen dioxide

Vasili L. Kasyutich, Philip A. Martin, Robert J. Holdsworth

    Research output: Contribution to journalArticlepeer-review


    Phase-sensitive, off-axis cavity-enhanced absorption spectroscopy techniques with a rectangular pulse current modulated violet diode laser (∼404 nm) were applied to measurement of nitrogen dioxide (NO2) in diluted standard mixture and laboratory air. An optical cell of an NO 2 detector was bounded by two plano-concave mirrors with a diameter of 7.75 mm and a reflectivity of 0.999, separated by a distance of 43 cm. The phase shift measurements due to Rayleigh scattering extinction were used for calibration of the detector. NO2 sensitivities were extracted from synchronous measurements of either the cavity output light intensity or the phase shift induced by the cavity. NO2 noise equivalent detection limit (S/N ≤ 1) of 1-2 ppbv was demonstrated for the intensity measurements with a lock-in amplifier time constant of 1 s. From the Allan plot of the intensity measurements the NO2 minimum concentration was estimated to be 0.24 ppbv in 80 s at atmospheric pressure. © 2006 IOP Publishing Ltd.
    Original languageEnglish
    Pages (from-to)923-931
    Number of pages8
    JournalMeasurement Science and Technology
    Issue number4
    Publication statusPublished - 1 Apr 2006


    • Absorption
    • Cavity
    • Detector
    • Diode laser
    • Nitrogen dioxide
    • Phase shift


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