Diode laser spectroscopy using a calibration free phasor decomposition approach with RAM nulling

K.C. Ruxton, A. Chakraborty, A.J. McGettrick, K. Duffin, W. Johnstone, G. Stewart

Research output: Contribution to conferencePaper

Abstract

A limiting factor of tunable diode laser spectroscopy (TDLS) analysis is the large unwanted residual amplitude modulation (RAM) background present on the recovered 1st harmonic signal. A novel approach to remove the background RAM will be presented. This new technique will be used alongside the phasor decomposition method (PDM) [1], a calibration free technique for recovery of the absolute gas absorption line-shape. The RAM nulling method developed, successfully removes the background by optical cancellation. This is
achieved by placing a fibre delay line, which introduces a π phase change in the modulation signal, in parallel with the gas cell line. When these lines are coupled together the background signals are at anti-phase and hence cancel each other. The main benefit being that measurement sensitivity can be increased. Results illustrating RAM nulling whilst using the PDM technique for absorption line-shape recovery will be presented. Figure 1 shows a recorded PDM measurement illustrating the difference with and without RAM Nulling.
Original languageEnglish
Pages80
Number of pages1
Publication statusPublished - Jul 2009
Event7th International Conference on Tunable Diode Laser Spectroscopy - Zermatt, Switzerland
Duration: 13 Jul 200917 Jul 2009

Conference

Conference7th International Conference on Tunable Diode Laser Spectroscopy
CityZermatt, Switzerland
Period13/07/0917/07/09

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Keywords

  • tunable diode laser spectroscopy
  • residual amplitude modulation
  • phasor decomposition method
  • absolute gas absorption
  • optical cancellation

Cite this

Ruxton, K. C., Chakraborty, A., McGettrick, A. J., Duffin, K., Johnstone, W., & Stewart, G. (2009). Diode laser spectroscopy using a calibration free phasor decomposition approach with RAM nulling. 80. Paper presented at 7th International Conference on Tunable Diode Laser Spectroscopy, Zermatt, Switzerland, .