title: Analysis of photonic crystal waveguide gratings with coupled-mode theory and a finite-element method.
abstract: Both rod and air-hole types of photonic crystal waveguide gratings are proposed and their coupling coefficients and transmission characteristics are effectively investigated by using a simple coupled-mode theory combined with a finite-element method. The results obtained are compared with the results obtained by using a full numerical simulation method. A new definition for unperturbed waveguides is introduced to obtain accurate coupling coefficients. It is shown that, by using a pi-phase-shifted waveguide structure in the case of an air-hole type of photonic crystal waveguide grating, the coupling coefficient is strongly enhanced. The accuracy of the method is discussed through numerical examples of high-index-contrast waveguide gratings.
authors.affiliation: Division of Media and Network Technologies, Hokkaido University, Sapporo, Japan. fujisawa@dpo7.ice.eng.hokudai.ac.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Fujisawa
authors.forename: Masanori
authors.initials: M
authors.lastname: Koshiba