Characterization of Thin Absorbing Films Using Infrared Surface Plasmons

Abstract

A combination of infrared excitation of surface plasmons and guided mode resonances is used to accurately parameterize thin highly absorbing films. In most circumstances it is difficult to determine both the thickness and dielectric constants of such films even if they are metallic and therefore able to support surface plasmons. Indeed it is clearly shown how it is impossible to characterize highly absorbing metal films using the Kretschmann geometry. However using an experimental system combining the Kretschmann geometry with a small air-gap spacer between the thin layer of interest and a normal thick metal layer it is possible to uniquely characterize the thin layer.