Simultaneous determination of thickness and refractive index using Cauchy or Sellmeier formulas by the example of surface plasmon resonance study on ultrathin polysulfone film

A three-wavelength method based on Cauchy or Sellmeier formulas is proposed for simultaneous determination of the thickness and refractive index without using approximate expansions of the refraction index over the wavelength. The method is also applicable for the simultaneous determination of other optical characteristics together with the refractive index. To test the applicability of the proposed method, the refractive index and thickness of ultrathin polysulfone film were obtained in the surface plasmon resonance experiment.