Band splitting and modal dispersion induced by symmetry braking in coupled-resonator slowlight waveguide structures.

We study the dispersion relations in slow-light waveguide structures consisting of coupled microdisk resonators. A group theoretical analysis of the symmetry properties of the propagating modes reveals a fundamental phenomenon: The degeneracy of the CW and CCW rotating modes is removed, giving rise to two distinct transmission bands. This effect induces symmetry-based dispersion which may limit the usable bandwidth of such structures. The properties of this band splitting and its impact on CROW performance for optical communications are studied in detail.