IMPURITY BANDS IN PHOTONIC INSULATORS

A chain of impurity cells in a photonic insulator introduces impurity modes of the electromagnetic held over a narrow band of frequencies. W e introduce a model of this band in the manner of a tight-binding desc ription of impurity bands in semiconductors, and use it to describe wa veguiding along the chain, and, in particular, across a corner of 90 d egrees. We also point out the possibility of using impurity bands in p hotonic insulators to study wave propagation along an effectively one- dimensional disordered chain. [S0163-1829(98)11919-7].