Abstract

An anodically oxidized alumina film includes numerous cylindrical micropores oriented parallel to each other and located at a spacing much smaller than the wavelength of light. By electroplating metals into the pores, a lattice of metallic columns can be constructed in the film that works as a wire grid type polarizer. We have fabricated a nickel-implanted alumina film by using sulfuric acid and nickel sulfamate. The extinction ratio of the prepared sample was >30 dB at a wavelength of 1.3 μm. On the other hand, when the pores are filled with suitable dielectric materials, the film becomes birefringent and works as a retardation plate. Using a He-Ne laser (λ = 0.63 (μm), we examined the alumina film with water in its pores and found that the refractive index varies as much as 4 X 10⁻³ depending on the direction of polarization. We have also developed a theory to predict these optical properties from the analysis of the electromagnetic field around the columns.

© 1989 Optical Society of America