Time-resolved photothermal breath analysis

Infrared laser spectroscopy allows the sensitive detection of gaseous substances. We present a novel gas sensing approach based on photothermal common-path interferometry that offers parts-per-billion sensitivity in microliter volumes: The thermal lens distortion pattern imprinted onto a near-infrared probe beam by the absorption of an infrared pump laser serves as signal for the sensing of low trace substance concentrations in the ppb range. Next to high specific sensitivity, additional focus lies on a tiny measurement volume and a compact overall setup. The advantages of this approach are discussed at the example of real-time measurements of breath N2O.