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A three-dimensional model for beam propagation through optical interference filters is presented. The model predicts a wavelength-dependent lateral beam displacement of tens or hundreds of micrometers in narrowband filters at an angle of incidence of only 3° to 5°. The effects of filter bandwidth, wavelength offset, angle of incidence, and beam size are investigated. The effect is experimentally confirmed for a 100 GHz filter at a 3.5° angle of incidence.

Electron-beam-deposited zirconia (zirconium dioxide) films are known to be inhomogeneous. They have a higher refractive index near the substrate and a lower index at the outer surface. Zirconia films deposited on high temperature (300°C) substrates are also known to be crystalline, exhibiting both a cubic and a monoclinic phase. X-ray diffraction studies of zirconia films of various thicknesses show that films which have an optical thickness of less than a quarter of a wavelength at 600 nm are cubic, while films that are thicker consist of both cubic and monoclinic zirconia. As the film thickness increases beyond a quarterwave optical thickness of 600 nm, the amount of the cubic phase remains constant and the amount of the monoclinic phase increases linearly with thickness. This implies that the film nucleates with a cubic structure but that after the film reaches a critical thickness, the surface conditions become more favorable for the growth of the monoclinic phase. This also suggests several possible models for the inhomogeneity in index. Spectral analysis indicates that the cubic portion of the film is optically inhomogeneous, while the monoclinic phase is homogeneous and has a lower refractive index.

Results are given of the analysis at five different laboratories of an unknown optical multilayer coating. In all, eleven different analytical and laboratory techniques were applied to the problem. The multilayer nominally consisted of three dielectric and two metallic layers. It was demonstrated convincingly that with present day techniques it is possible to determine the basic structure of such a coating.