Quantum-cascade-laser-based optoacoustic detection for breath sensor applications

Continuous wave, thermoelectrically cooled, quantum cascade laser based sensor platform for the quantitative detection of exhaled human breath is reported. The sensor is based on a 2f wavelength modulation quartz enhanced photoacoustic spectroscopy (QEPAS) technique, which is very well suited for real time breath analysis, due to the fast gas exchange inside a compact QEPAS gas cell. The quantum cascade laser has be designed to target the interference-free NO absorption line at 1900.075 cm
^-1
. A 1s minimum detectable concentration of ~ 8 parts per billion in volume with 1 sec time resolution was obtained. Preliminary breath test demonstrated extremely fast response and fast signal decay.