Trace gas spectroscopy using state-of-the- art mid-infrared semiconductor laser sources: progress, status, and applications

The recent development of interband cascade lasers (ICLs) and quantum cascade lasers (QCLs) based trace gas sensors enables the targeting of strong fundamental rotational-vibrational transitions in the mid-infrared, which are one to two orders of magnitude more intense than transitions in the near-infrared. This has led to the development of mid-infrared compact, field deployable sensors based on two sensor system platforms, laser absorption and quartz enhanced spectroscopy. These sensor platforms are applicable for environmental monitoring, atmospheric chemistry and for use in the petrochemical industry. The spectroscopic detection and monitoring of three molecular species, methane (CH₄), ethane (C₂H₆) [1], formaldehyde (H₂CO) [2] and hydrogen sulphide (H₂S) [3] will be described.