Sub-parts-per-billion level detection of SF6 with a fiber-coupled QCL-QEPAS sensor

The detection and quantification of trace chemical species in the gas phase is of great interest in a wide range of applications such as environmental monitoring, industrial process control and medical diagnostics. In combination quantum cascade laser (QCLs), quartz enhanced photoacoustic spectroscopy (QEPAS) offers the advantage of high sensitivity and fast time-response. Very efficient QCL-based QEPAS sensors have been demonstrated for trace detection of several chemical species, such as NH3, NO, CO2, N2O, CO, CH2O, etc. Small size sensors with simple optical alignment has been realized employing fiber-coupled system between near IR laser source and QEPAS spectrophones, thus the possibility to extend this approach also for mid-IR light sources, considering the small size of the QEPAS module, may allow compact integration also with QCLs.