Slow-light tailoring in photonic crystal waveguides through additional longitudinal periodicity

Photonic crystals waveguides (PhCWs) can be engineered to obtain reduced group velocity regions and tailored GVD properties by changing the waveguide width, or the size of some holes in the PhC lattice. These approaches modify transversally the PhCW geometry. Weakly coupled cavities implemented in CROW PhCW design or in ring resonator chains have also demonstrated large delays due to sharp resonances but on a limited wavelength range. We propose here to break the translational symmetry along the longitudinal axis creating strongly coupled cavities thus operating on a broad, softened resonance leading, in turn, to a reasonable delay with the advantage of a large wavelength range.