Quantum cascade laser sensor for SO2 and SO3 for application to combustor exhaust streams

We have demonstrated a high-sensitivity, room-temperature quantum-cascade (QC) laser sensor for detection of SO2 and SO3 under conditions relevant to aircraft test combustor exhaust. Two QC lasers probe infrared absorption features at 7.50 and 7.16 (mu)m for SO2 and SO3, respectively, with a common dualbeam detection system. We inferred a noise-equivalent absorbance of ~1*10^-4 Hz-1/2. We have demonstrated detection limits for both SO2 and SO3 of 1-2 ppmv m/Hz1/2 (where ppmv is parts in 106 by volume) for 300 torr, elevated temperature, and path lengths near 1 m. This level of sensitivity permits measurement of <1 ppmv of SO2 and SO3 at these conditions with modest signal averaging.