23 September 2002 Highly sensitive detection of trace gases using pulsed quantum cascade lasers
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We show that by using a high resolution Fourier transform infrared spectrometer we can map the temporal characteristics of a pulsed quantum cascade laser into the wavenumber domain, and hence show that when a square current pulse is applied to a distributed feedback laser a linear sub-microsecond frequency chirp is developed. We describe a mid infrared spectrometer, that is based upon the use of this linear chirp, which can provide a real-time display of the spectral fingerprint of molecular gases. The sensitivity of the spectrometer is based upon the use of long pathlength White or Herriot cells, and the multiplex advantage associated with recording the entire spectral window during each electrical pulse. For a cell with a path length of 9.6 m, dilution measurements made on the ν9 band transistions of 1,1 difluoroethylene indicate a sensitivity of 30 parts per billion.
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Geoffrey Duxbury, Geoffrey Duxbury, Erwan L. Normand, Erwan L. Normand, Nigel Langford, Nigel Langford, Michael T. McCulloch, Michael T. McCulloch, Stephen Walker, Stephen Walker, } "Highly sensitive detection of trace gases using pulsed quantum cascade lasers", Proc. SPIE 4817, Diode Lasers and Applications in Atmospheric Sensing, (23 September 2002); doi: 10.1117/12.451459; https://doi.org/10.1117/12.451459

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