Carbonyl sulfide detection with a thermoelectric ally cooled midinfrared quantum cascade laser

A compact absorption spectrometer with a midinfrared tunable quantum cascade laser operating at 4.86 mum (2054 cm(-1)) is used to measure lower concentrations of carbonyl sulfide (COS) in air. A detection sensitivity of similar to30 parts in 10(9) of COS and the selectivity of two stable isotopes, (COS)-C-12-O-16-S-32 and (COS)-C-12-O-16-S-34, are demonstrated. Specifically, the feasibility of detecting COS in expired human breath as a potential noninvasive medical diagnostic tool is investigated. (C) 2003 Optical Society of America.