In this paper, the use of a total absorption attenuated total reflection (ATR) method to measure complex refractive indices and thicknesses of thin foils is discussed. Our studies show that in a prism metal-foil coupling system, the gap thickness between the prism and the metal-foil modifies the state of the coupled surface plasmons on the metal-foil interface, and yields total absorption at three different incident angles, under optimum conditions, respectively. The dependence of the conditions for total absorption on the complex refractive index and on the foil thickness is discussed. By preparing three prism coupling systems with different refractive indices, and by measuring the incident angle at minimum reflectance in each system, complex refractive indices and foil thicknesses of thin gold-foils have been measured.
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