MEASUREMENT OF NITRIC-OXIDE WITH AN ANTIMONIDE DIODE-LASER

An antimonide diode laser operating near 2.65 mu m was used to measure absorption lines of NO gas in the first overtone band. A blended line pair of NO that is sufficiently free of interference from H2O to perm it the selective detection of NO under reduced pressure conditions was identified. With wavelength-modulation spectroscopy, a rms noise leve l equivalent to an absorbance of 3.2 x 10(-6) was achieved at a measur ement integration time (for a single spectral data point) of 0.1 s. Th e corresponding detection sensitivity (signal-to-noise ratio of 2) for NO in air at reduced pressure was similar to 15 ppm m (ppm is parts i n 10(6)). Antimonide diode lasers show substantial promise for gas-sen sing applications because they can gain access to relatively strong ab sorption lines of several gases of environmental interest at operating wavelengths at which cryogenic cooling is not required. (C) 1997 Opti cal Society of America.