OPTICAL-PROPERTIES OF A METAL-FILM AND ITS APPLICATION AS AN INFRARED ABSORBER AND AS A BEAM SPLITTER

The optical properties of a thin metal film are derived, with a thin film defined as having a thickness smaller than the wavelength of the radiation and the skin depth. The derivation is based on the continuity equation for the electric field and on the energy balance for the incident, reflected, transmitted, and absorbed energy current. The use of thin metal films as anti-interference coatings, as absorbers for the infrared, as semitransparent mirrors in interferometric devices and beam splitters, and as mirrors is discussed.