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 π-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.
© 2006 Optical Society of America
Original Manuscript: September 30, 2005
Revised Manuscript: January 12, 2006
Manuscript Accepted: January 15, 2006
Takeshi Fujisawa and Masanori Koshiba, "Analysis of photonic crystal waveguide gratings with coupled-mode theory and a finite-element method," Appl. Opt. 45, 4114-4121 (2006)