Laser Absorption spectroscopy to probe chemically reacting flows

Laser absorption spectroscopy is now a well established tool to perform temperature, density and velocity measurements in a wide variety of aerodynamic and combustion flows. Measurements are usually performed on heterogeneous molecules like NO, CO, CO2 and H2O which present strong absorption line strengths in the infrared region due to their high dipole moments. In this paper, we present examples of applications using mid-infrared laser diodes in several hypersonic wind tunnels and combustion facilities of Onera and DLR followed by a review of actual developments in new OPO based laser sources providing better coverage of the infrared domain and opening new possibilities of ultra sensitive detection using cavity enhanced or photo-acoustic methods and stand-off distance measurements based on lidar schemes.