Article

Applied Physics B

, Volume 79, Issue 4, pp 525-530

Multi-component chemical analysis of gas mixtures using a continuously tuneable lidar system

  • P. WeibringAffiliated withDepartment of Physics, Lund Institute of Technology
  • , C. AbrahamssonAffiliated withDepartment of Physics, Lund Institute of Technology Email author 
  • , M. SjöholmAffiliated withDepartment of Physics, Lund Institute of Technology
  • , J.N. SmithAffiliated withDepartment of Physics, Lund Institute of Technology
  • , H. EdnerAffiliated withDepartment of Physics, Lund Institute of Technology
  • , S. SvanbergAffiliated withDepartment of Physics, Lund Institute of Technology

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Abstract

Differential absorption lidar (DIAL) measurements are usually made on single compounds by alternately switching the wavelength between on and off a resonance line. The selection of more than two wavelengths is a mathematical necessity for simultaneous measurement of multiple species or for resolving interference effects between a compound of interest and a background gas such as water vapour or carbon dioxide. This is especially true in the mid-IR region, where many hydrocarbon compounds have important spectral features. We present a method for remote measurement of gas mixtures in the mid-IR region based on a newly developed fast-switching, frequency-agile optical parametric oscillator lidar transmitter. A multivariate statistical procedure has also been applied for this system, which combines a genetic algorithm for wavelength selection with a partial least squares method for identifying individual compounds from their combined absorption spectrum. A calibration transfer is performed for compounds of interest using reference spectra from an absorption spectra database. Both indoor absorption cell measurements and outdoor remote range resolved measurements of hydrocarbon mixtures were performed to explore the performance of the method.