Role of granular structure in metal layers on the optical properties of absorbing mirrors

Abstract

Absorbing mirrors are optical thin film systems consisting of an absorbing metal layer held by a transparent interlayer in defined distance to a (metal) mirror layer. In the reflected light, such three-layer systems show vivid color effects due to the absorption in the metal. This absorption is modified and enhanced by interference effects. The interference condition can be tuned by the thickness of the transparent interlayer. We show by experimentation and by stratified medium model calculations the importance of a nanoscale granular structure in the absorbing metal layer for obtaining a wide spectral range of the color effect.