In the almost fifty years that have gone by since the first volume of _Progress in Optics_ was published, optics has become one of the most dynamic fields of science. The volumes in this series that have appeared up to now contain more than 300 review articles by distinguished research workers, which have become permanent records for many important developments. * Invariant Optical Fields * Quantum Optics in Structured Media * Polarization and Coherence Optics * Optical Quantum Computation * Photonic Crystals * Lase Beam-Splitting Gratings