OXYGEN SENSING USING SINGLE-FREQUENCY DFB LASER-DIODES ART LAMBDA = 761 NM

Oxygen O-2 sensing using high-resolution direct optical absorption wit h a single mode GaAs-AlGaAs distributed feedback (DFB) laser diode emi tting at a wavelength around 761 nm which coincides with the b(1) Sigm a(g)(+) (v' = 0) <-- X-3 Sigma(g)(-) (v '' = 0) electronic transition band is reported. In particular, issues relevant to O-2 sensing in the high concentration regime, not previously of concern for trace gas se nsing, are investigated. While detectivity of 20 ppm over a 1 m pathle ngth is determined, the need for careful consideration of parameters s uch as linearity, dynamic range and calibration and the effect of pres sure-induced broadening on sensitivity is highlighted. (C) 1997 Elsevi er Science S.A.