Miniaturized laser-based photoacoustic sensor of trace gases

Abstract

A photoacoustic resonant cell intended for laser sensing of trace gases is represented. The cell is adapted so as to enhance the gas-detection performance and, simultaneously, to reduce the cell size. The cell design provides an efficient cancellation of the window background (a parasite response due to absorption of laser beam in the cell windows) and acoustic isolation from the environment for an acoustic resonance of the cell. The useful photoacoustic response from a detected gas, window background and noise are analyzed in experiments as functions of the modulation frequency for a prototype photoacoustic cell with the internal volume ∼ 0.5 cm3. The minimal detectable absorption for the prototype is estimated to be ∼ 1.2·10−8 cm−1 W Hz−1/2.