12 February 2008 A quantum cascade laser based room temperature spectrometer for sensitive detection of ammonia and ethylene
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Abstract
We investigated the use of a pulsed, distributed feedback (DFB) quantum cascade (QC) laser centered at 970 cm-1 in combination with an astigmatic Herriot cell with 150 m path length for the detection of ammonia and ethylene. This spectrometer utilizes the intra-pulse method, where a linear frequency down-chirp, that is induced when a top-hat current pulse is applied to the laser, is used for sweeping across the absorption line. This provides a real time display of the spectral fingerprint of molecular gases, which can be a few wave numbers wide. A 200 ns long pulse was used for these measurements which resulted in a spectral window of ~1.74 cm-1. A room temperature mercury-cadmium-telluride detector was used, resulting in a completely cryogen free spectrometer. We demonstrated detection limits of ~3 ppb for ammonia and ~5 ppb for ethylene with less than 10 s averaging time.
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J. Manne, J. Manne, W. Jäger, W. Jäger, J. Tulip, J. Tulip, } "A quantum cascade laser based room temperature spectrometer for sensitive detection of ammonia and ethylene", Proc. SPIE 6900, Quantum Sensing and Nanophotonic Devices V, 690014 (12 February 2008); doi: 10.1117/12.785478; https://doi.org/10.1117/12.785478
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