Slow-light dispersion properties of multiatomic multiband coupled-resonator optical waveguides

In this paper, we investigate the dispersion properties of a multiatomic coupled-resonator optical waveguide (CROW), and show the existence of band-dependent group velocities in its slow-light bands. By including the next-nearest-neighbor coupling terms in a coupled-mode theory (CMT) analysis for the structure, we explain the physical origin of the band-dependent group velocities in terms of the modification of molecular mode-coupling strengths, and also derive the criteria for complete band separation and perfect intermode intensity overlap. Our results imply that when estimating the performance of a multiwave slow-light device, the band dependency of group velocities must also be considered in addition to the conventional CROW dispersion. Numerical analysis with a photonic crystal platform shows excellent agreement with theory.