The physical vapor deposition process of serial bideposition is adapted to the fabrication of uniaxial optical coatings. During the coating process the vapor impinges at an angle of incidence of about 70 • on to the substrate, and a stepwise axial rotation with 90 • increments causes a columnar structure to grow normal to the substrate. Symmetry considerations that follow from the choice of 90 • for the stepwise increment ensure that the film is achiral and has negligible in-plane linear

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... ngence. Optical characterization techniques confirm that films of tantalum oxide, titanium oxide and zirconium oxide are positive uniaxial with n e − n o in the range 0.10 to 0.14.