Abstract

One of the motivations for ongoing intensive study of photonic bandgap materials (photonic crystals) is the possibility to create localized photon modes. The main idea is that such a mode emerges when a defect is introduced into the crystal. The frequency of the mode lies within the bandgap, while the field of the defect-induced mode falls off exponentially away from the defect. The types of defects considered in the literature can be conventonally divided into two groups. Namely, pointlike scatterers, i.e., local perturbations of the spatially periodic dielectric constant, and periodicity interruption or, in other words, the phase slips. While both types of defects cause the formation of the in-gap states, there is a fundamental difference between them. A point-like defect does not lift the long-range order of the underlying crystal. On the contrary, in the presence of a phase-slip, the distance between two lattice sites located to the left and to the right from the phase slip is noninteger (in the units of the lattice constant). Lately, the properties of defects in photonic bandgap structures (phase-slip-like and more complex defects, specifically designed for certain manipulations of the light flow) have become a branch of research of its own.

© 2003 Optical Society of America