TABLE OF CONTENTS All the materials discussed in the main text of this book were produced by nature. Well, not by nature alone, we did certainly help nature here and there. We combined the elements in a manner which led to a variety of new properties. We managed to persuade some crystals to grow under circumstances when they were most reluctant to do so. We produced structures with the thickness of a single atom, but we were always restricted by the ways atoms were willing to arrange themselves. An artificial material, on the other hand, comes about by taking an entirely innocuous dielectric, immersing into it some microscopic structure, and lo and behold, its electrical behaviour radically changes.
The idea of producing artificial materials is not new. It has been known for about three scores of years that inclusion of bits of metal in a dielectric will lead to some modest change in the dielectric constant. There were, however, some new developments in the last decade which we should no longer ignore. They could be roughly divided into two classes. In one case the distance between the inclusions is comparable with the wavelength, in the other case it is small relative to the wavelength. The first one is known as the subject of photonic band gaps and the second one as metamaterials. The first one is based on the Bragg effect which came repeatedly into our treatment (X-ray and electron diffraction, the Ziman model of electronic band gaps, volume holography, phase...
