QUANTUM ELECTRODYNAMICS OF LOCALIZED LIGHT

Recent experiments have confirmed the occurrence of photon mobility edges and photonic band gaps for microwave radiation in strongly scattering dielectrics. This suggests that similar phenomena may soon be observed at optical frequencies. The localization of light gives rise to fundamental modifications in the radiative properties of atoms and molecules. We discuss the occurrence of novel dressed atomic states, photon-atom bound states and vacuum Rabi atomic line splittings within these novel dielectric materials. It is suggested that the photonic band gap protects these dressed atomic states from homogeneous collision broadening when the temperature is small compared to the electromagnetic energy gap. When a finite density of impurity atoms with an optical transition in the photonic band gap is present, the atomic resonance dipole-dipole interaction leads to the formation of a narrow photonic impurity band within the larger gap. This suggests new frontiers in laser physics, nonlinear optics and photochemistry.