Photonic crystals: working at the speed of light

Summary form only given. During the last several years, a very innovative and exciting new class of materials has emerged called photonic band gap materials, or photonic crystals, for simplicity. The basic idea is to design materials that can control the properties of electromagnetic waves (photons) in much the same way that a semiconductor crystal controls the properties of electrons. Therefore, if one were to construct a material consisting of a periodic array of macroscopic uniform "dielectric atoms", then, as in the case of electrons, the photons in this crystal could be described in terms of a band structure. The beauty of possessing a band structure is the possibility of having a complete (or omnidirectional) photonic band gap, i.e. a range of frequencies for which photons are forbidden to travel within the crystal for any direction of propagation.