2006 Volume 34 Issue 4 Pages 275-282
There is an increasing need in many chemical sensing applications ranging from environmental science to industrial process control as well as medical diagnostics for fast, sensitive, and selective trace gas detection based on laser spectroscopy. The recent availability of novel pulsed and continuous wave (cw) quantum and interband cascade distributed feedback (QC and IC DFB) lasers as mid-infrared spectroscopic sources addresses this need. A number of spectroscopic techniques have been demonstrated worldwide. For example, the authors have employed infrared DFB QC and IC lasers for the detection and quantification of trace gases and isotopic species in ambient air at ppmv, ppbv and even sub-ppbv levels by means of direct absorption, cavity enhanced, photoacoustic and wavelength modulation spectroscopy.