From photonic band gaps to refractive index engineering

Since the pioneering work of Yablonovitch ten years ago, photonic band gap (PBG) materials have become the subject of a well-established domain of electromagnetism, with well-defined branches dealing with microwave engineering, quantum optics, semiconductor technology or laser theory. The resolution of Maxwell's equations in three-dimensional (3D) resonant structures is more than ever the key point. This paper reviews the state-of-the-art of photonic band gap materials. It seems that, after the early years devoted to understanding simple and standard structures (i.e. highly symmetric, infinite or perfectly two-dimensional, or with simple planar boundaries, ...), the way from photonic crystal concepts to real photonic structures requires now to go one step further towards complexity, towards a complete three-dimensional refractive index engineering. (C) 1999 Elsevier Science B.V. All rights reserved.