Diode-Laser Sensors for In-Situ Gas Analysis

Optical sensors based on semiconductor lasers are at the threshold of routine applications in gas analysis and increasingly these sensors are used for industrial and environmental monitoring applications whenever sensitive, selective and fast in-situ analysis in the near- and mid-infrared spectral region is required. With the increasing complexity of processes, online gas analysis is becoming an issue in automated control of various industrial applications such as combustion and plasma diagnostics, investigations of engines and automobile exhaust measurements. Other challenges are online analysis of high purity process gases, medical diagnostics and monitoring of agricultural and industrial emissions (VDI 2002). The need to meet increasingly stringent environmental and legislative requirements has led to the development of analyzers to measure concentrations of a variety of gases based on near- and mid-infrared absorption spectroscopy.