ABSORPTION-MEASUREMENTS OF THE 2ND OVERTONE BAND OF NO IN AMBIENT ANDCOMBUSTION GASES WITH A 1.8-MU-M ROOM-TEMPERATURE DIODE-LASER

We describe the development of a room-temperature diode sensor for in situ monitoring of combustion-generated NO. The sensor is based on a n ear-IR diode laser operating near 1.8 mu m, which probes isolated tran sitions in the second overtone (3,0) absorption band of NO. Based on a bsorption cell data, the sensitivity for ambient atmospheric pressure conditions is of the order of 30 parts in 10(6) by volume for a meter path (ppmv-m), assuming a minimum measurable absorbance of 10(-5). Ini tial H-2-air flame measurements are complicated by strong water vapor absorption features that constrain the available gain and dynamic rang e of the present detection system. Preliminary results suggest that de tection limits in this environment of the order of 140 ppmv-m could be achieved with optimum baseline correction. (C) 1997 Optical Society o f America.