Sub ppb CO Gas Measurement Using a Non Invasive QCL Laser Absorption Spectrometer Technique

A sensitive gas detection system using a distributed feedback CW Quantum Cascade Laser (QCL) centered at 4610 nm as a radiation source has been developed. QCL was used in combination with an off-axis integrated cavity output spectroscopy (ICOS) for Carbon Monoxide (CO) gas detection in a low gas pressure. a 15 cm long high-finesse cavity with an effective optical path length of 400 m has been used as a sample gas cell. We demonstrated detection limit of 1 ppbv with less than 2 second averaging time. The best detection limit is obtained at 0.4 ppbv for a 128 s acquisition time. All measurement results has shown that the QCL based ICOS detector system proved to be suitable for monitoring CO gas in a low gas pressure condition with sub-ppb sensitivity.