Determining the refractive index dispersion and thickness of hot-pressed chalcogenide thin films from an improved Swanepoel method

Y. Z. Fang, D. Jayasuriya, David Furniss, Z. Q. Tang, Michal Sojka, Christos Markos, Slawomir Sujecki, Angela B. Seddon, Trevor M. Benson

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The well-known method presented by Swanepoel can be used to determine the refractive index dispersion of thin films in the near-infrared region from wavelength values at maxima and minima, only, of the transmission interference fringes. In order to extend this method into the mid-infrared spectral region (our measurements are over the wavelength range from 2 to 25 µm), the method is improved by using a two-term Sellmeier model instead of the Cauchy model as the dispersive equation. Chalcogenide thin films of nominal batch composition As40Se60 (at.%) and Ge16As24Se15.5Te44.5 (at.%) are prepared by a hot-pressing technique. The refractive index dispersion of the chalcogenide thin films is determined by the improved method with a standard deviation of less than 0.0027. The accuracy of the method is shown to be better than 0.4% at a wavelength of 3.1 µm by comparison with a benchmark refractive index value obtained from prism measurements on Ge16As24Se15.5Te44.5 material taken from the same batch.
Original languageEnglish
Article number237
JournalOptical and Quantum Electronics
Issue number7
Number of pages19
Publication statusPublished - 2017


  • Chalcogenide glasses
  • Refractive index
  • Dispersion

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