Mid-infrared Laser Based Gas Sensor Technologies for Environmental Monitoring, Medical Diagnostics, Industrial and Security Applications

Abstract

Recent advances in the development of compact sensors based on mid-infrared continuous wave (CW), thermoelectrically cooled (TEC) and room temperature operated quantum cascade lasers (QCLs) for the detection, quantifi ca-tion and monitoring of trace gas species and their applications in environmental and industrial process analysis will be reported. These sensors employ a 2 f wavelength modulation (WM) technique based on quartz enhanced photoacoustic spectroscopy (QEPAS) that achieves detection sensitivity at the ppbv and sub ppbv concentration levels. The merits of QEPAS include an ultra-compact, rugged sensing module, with wide dynamic range and immunity to environmental acoustic noise. QCLs are convenient QEPAS excitation sources that permit the targeting of strong fundamental rotational-vibrational transitions which are one to two orders of magnitude more intense in the mid-infrared than overtone transitions in the near infrared spectral region.