Vol. 38, Issue 2, pp. 341-352

Abstract

A photoacoustic sensor using a laser diode emitting near 1573 nm in combination with a dual-microphone resonant photoacoustic cell has been developed for carbon dioxide trace gas analysis at atmospheric pressure. Wavelength-modulation scheme and 1f detection for CO₂ concentration measurements in Ar are demonstrated. The noise equivalent absorption sensitivity of NEAS(1σ) = 1.01×10^–8 Wcm^–1/Hz^1/2, corresponding to a detection limit of 30 parts in 10⁶ by volume (ppmv) for a 100 s integration time and 4.5 mW average laser power. The photoacoustic response of CO₂ dependence on the buffer gases with different mixture ratio of Ar and N₂ was investigated. Finally, the possibility to make use of the sensor for measurements of ambient CO₂ is also presented.