title: Admittance diagrams of accidental and premeditated optical inhomogeneities in coatings.
abstract: Intuitive interpretation of the effect of inhomogeneous layers in optical coatings is often difficult. I use admittance diagrams to interpret some properties of accidental and premeditated optical inhomogeneities. The effect of accidental homogeneous and inhomogeneous transition layers on the spectral properties of a single film is presented. I show that such layers affect the envelope of the reflectance spectra of thick films, effects that are extended to the shorter wavelength range. Using the same approach, I evaluate the properties and limitations of quintic antireflection coatings and show that the suppression of harmonics in rugate filters is due to an absentee-layer phenomenon and not solely to an antireflection effect as is often suggested.
authors.affiliation: Institute for Microstructural Sciences, National Research Council of Canada, Ottawa, Ontario. daniel.poitras@nrc.ca
authors.forename: Daniel
authors.initials: D
authors.lastname: Poitras