Abstract

We report studies of Pb_1−xSn_xTe and Pb_1−xGe_x Te laser characteristics which affect their performance in high-sensitivity gas analysis. In Pb_1−xSn_xTe, the rates at which the energy gap E_g and the individual cavity mode frequencies $\overline{\nu }$ tune with current are consistent with published data. Single-mode operation typically occurs near threshold; at higher currents, multimode operation is common. In Pb_1−xGe_xTe, E_g and $\overline{\nu }$ tune more slowly, and multimode operation generally occurs. High-resolution absorption measurements on C₂H₄ (950 cm⁻¹) and NH₃ (931 cm⁻¹) indicate that the frequency reproducibility of the lasers is adequate for trace gas analysis. Such analysis has been performed on calibrated samples of C₂H₄ in N₂ at atmospheric pressure. The minimum detectable C₂H₄ concentration for a 10-cm path was between 17 ppm and 50 ppm, in good agreement with the 30 ppm estimated for detector-noise-limited operation. Effects of detector and laser noise on detection sensitivity are discussed.

© 1976 Optical Society of America

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