Abstract

A dielectric material with a 3-D periodicity may have a photonic gap in its frequency spectrum in which propagating electromagnetic modes are forbidden.¹ Recently, a number of materials that have such a gap have been discovered.²,³ Electromagnetic modes with frequencies in this forbidden region must be localized in all three dimensions. We show that lattice imperfections can introduce such exponentially localized states in the photonic band gap. We focus on the frequency spectrum of dielectric structures containing defects in an FCC lattices of nonspherical atoms,³ and compare the results of our calculations with the experiments of Yablonovitch. We consider impurities of two types: air spheres in the dielectric region and dielectric spheres in the air region. In both cases, localized photon modes are found to be introduced into the gap. Variation of the size of the impurity sphere leads to complete tunability of the frequency of this localized mode. We also discuss the localization of light at the surface of a photonic band-gap material.

© 1991 Optical Society of America