Passive remote detection in a combustion system with a tunable heterodyne receiver: application to sulfur dioxide

Here is presented the possibility of remote detection of sulfur dioxide in a combustion chamber. It is of major interest as part of the program of global pollution reduction. The remote detection of combustion products in the middle infrared region can be very useful for engine diagnostics or industrial pollution control. We used a tunable diode laser heterodyne receiver working in the middle infrared. Such an apparatus is able to perform passive emission spectroscopy on distant sources. It is a very sensitive and selective technique for radiation detection able to extract weak signals from the background. To validate our prototype and demonstrate its efficiency, we recorded high-temperature sulfur dioxide emission spectra around 1336 cm-1 (ν3 ro-vibrational band), in the case of a polluted CH4/air flame