title: Graded index profile of anodic alumina films that is induced by conical pores.
abstract: The size and the shape of micropores in anodic alumina films are studied by electron microscope observation and mercury intrusion porosimetry. Pores have conical shapes with ~ 10-nm diameters and are widened at the rate of ~ 0.05 nm/min by immersion in a sulfuric acid solution. Such conical pores give rise to the refractive-index distribution and anisotropy in the alumina films. By analyzing interference fringes, we find that a graded-index profile, as well as birefringence, exists in the anodic alumina films. The experimental results are in good agreement with theoretical predictions.
authors.forename: L F
authors.initials: LF
authors.lastname: Huang
authors.forename: M
authors.initials: M
authors.lastname: Saito
authors.forename: M
authors.initials: M
authors.lastname: Miyagi
authors.forename: K
authors.initials: K
authors.lastname: Wada