ABSTRACT

Periodic order in a dielectric microstructure provides coherent scattering of light from a precise geometrical arrangement of nearly identical scatterers. Bragg scattering resonances lead to the formation of stop gaps, where destructive wave interference prevents light propagation in specic directions over specic frequency ranges. These wave interference effects lead to a redistribution of the electromagnetic density of states as a function of frequency. In some frequency intervals this can result in a very “high” density of states, consisting of “slow” modes with a greatly reduced velocity for energy transport. In other frequency intervals, if the scattering is strong enough, this can lead to the complete absence of electromagnetic modes propagating in any direction. Such a frequency interval is referred to as a photonic band gap (PBG). The attainability of a PBG for waves obeying Maxwell’s equations, using nonabsorbing dielectric materials, was rst proposed in 1987. The occurrence of a PBG in certain articial periodic microstructures has been the starting point of a broad and interdisciplinary eld of research.