title: Focusing of electromagnetic waves by periodic arrays of air holes with gradually varying radii.
abstract: We study theoretically the focusing effects when a Gaussian beam passing through a graded photonic crystal consisting of air holes with gradually varying radii. The device is used to couple the light between the conventional and photonic crystal waveguides. The coupling efficient is about 4 times higher than that by the linear taper structure.
authors.forename: Hung-Ta
authors.initials: HT
authors.lastname: Chien
authors.forename: Chii-Chang
authors.initials: CC
authors.lastname: Chen