Apodized photonic crystal waveguide gratings.

Apodized photonic crystal (PC) waveguide gratings are proposed to suppress sidelobes which appear in reflection spectra of usual PC waveguide gratings. By using specific functions (Gauss and Gauss-cosine functions) for the longitudinal refractive index distribution, it is possible to suppress sidelobes in the reflection spectra of PC waveguide gratings efficiently. The apodization is realized by simply changing diameters of dielectric pillars adjacent to the PC waveguide core. It is shown that by using Gauss-cosine functions for the apodization, Bragg frequency of the waveguide grating becomes insensitive to the magnitude of perturbation leading to the possibility of designing waveguide gratings with arbitrarily Bragg frequency and bandwidth by modulating geometrical parameters only.