BOUND-STATES IN PHOTONIC CRYSTAL WAVE-GUIDES AND WAVE-GUIDE BENDS

We investigate the mechanism for the appearance of bound states in two -dimensional photonic crystal waveguides and contrast it with the corr esponding mechanism for conventional guides. It is shown that the peri odicity of the ph(atonic crystal can give rise to frequency ranges abo ve cutoff where no guided modes exist in the waveguides. Such mode gap s make possible the creation of bound states in constrictions and in b ends. Bound states are found to correspond to analogous cavity modes a nd it is shown that their appearance strongly depends on the lattice g eometry and cannot be described in a one-dimensional framework.