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PublisherThe University of Arizona.
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AbstractWe consider in this work the contribution of anisotropic microstructure to polarization effects in thin films. The microstructure is pictured by a simple model as composed of identical columns with elliptical cross section elongated in a direction perpendicular to that of the vapor incidence. The asymmetry in columnar structure that results from oblique deposition is identified as the common source for the significant dichroism and birefringence observed in metal and dielectric films, respectively. A four-dimensional theory for multilayer systems is presented that starts from first principles, unifies previous treatments for particular cases of film anisotropy, and properly handles the most general case of elliptically polarized mode propagation. In this framework and from a set of polarimetric measurements, a simple method is devised, with explicit consideration of the anisotropic microstructure, for the determination of the physical thickness and principal refractive indices of a single dielectric film. A sequence of transmittance measurements is performed with a zirconium oxide film deposited at 65° and, substrate role and instrumental errors considered, good agreement is obtained between theory and experiment. Spectrophotometer data for a narrowband filter with 21 layers deposited at 30° is shown to confirm theoretical predictions of peak positions with Angstrom resolution. A hypothetical metal film is discussed that reproduces the essential features observed in the optical behavior of an aluminum film deposited at 85°. Potential applications and suggestions for future work are included.
Degree ProgramOptical Sciences