Mid-infrared Laser Based Gas Sensor Technologies for Environmental Monitoring, Medical Diagnostics, Industrial and Security Applications
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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, quantification and monitoring of trace gas species and their applications in environmental and industrial process analysis will be reported. These sensors employ a 2f 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.
KeywordsLaser spectroscopy Quartz enhanced photoacoustic spectroscopy Wavelength modulation spectroscopy Quantum cascade lasers Trace gas detection Carbon monoxide Nitric oxide
The Rice University group acknowledges financial support from a National Science Foundation (NSF) grant EEC-0540832 entitled “Mid-Infrared Technologies for Health and the Environment (MIRTHE)”, a NSF-ANR award for international collaboration in chemistry “Next generation of Compact Infrared Laser based Sensor for environmental monitoring (NexCILAS)” and grant C-0586 from the Robert Welch Foundation.
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