ABSTRACT
At the end of the twentieth century the start of research activity with photonic crystals (PhCs) required the method of introducing this new and rapidly growing eld in a clear way by drawing an analogy with some well-known phenomena from traditional solidstate physics. For semiconductor physics researchers, the simple way to understand the origin of a photonic band gap was to consider the processes lying in the basis of electron spectrum formation in crystalline semiconductors. Scientists working with x-rays may immediately nd an analogy between PhCs and x-ray diffraction on a periodic atomic lattice. For those who have studied acoustics, the propagation of sound in articially fabricated periodic systems mentioning PhCs often reminds of a modern art sculpture by Eusebio Sempere.1 This famous artwork consists of polished stainless-steel tubes located in periodic order on a base and blocks the propagation of sound waves in a certain frequency band. In the mid 1990s, sonic researchers introduced the term “phononic crystal” (PnC) in analogy with PhCs, which, at that time, already attracted an enormous amount of research groups.
