Optimum conditions in the attenuated total reflection technique.

In this paper the optimum condition for using the attenuated total reflection (ATR) technique is studied. In optimum conditions, the energy of an incident plane wave can be totally absorbed. The optimum condition can be realized by fabricating a localized thickness variation in the gap between a prism and a sample substrate with a point contact pressure. In the ATR technique, for example, the complex refractive index and the foil thickness of a thin metal foil, and the gap thickness are unknown parameters. To determine these unknown parameters, we prepared three prism coupling systems with different refractive indices. By this technique, we measured the complex refractive indices and the foil thicknesses of thin gold foils sputtered onto glass substrates, and the refractive index and the film thickness of a silica film sputtered onto a metal substrate.