Tunable Photonic Crystals

Abstract

In semiconductor materials electron waves propagate in a periodic potential, which originates from the atomic lattice. This modifies the dispersion relation of free electrons: A complicated bandstructure with a band gap is formed. A judicious incorporation of defects (doping) facilitates the manipulation of the electronic properties of these materials. For many decades now, it has been possible to tailor semiconductors to almost any need. The results are well-known: Almost all modern electronic devices are based on these materials, mainly on silicon. For about a decade now, the optical analogues to electronic semiconductors, the so-called Photonic Crystals (PCs), are the subject of intense international research efforts [1, 2]. PCs are materials with a periodically varying index of refraction, that facilitates the control over both propagation of light and — in case they exhibit a complete photonic band gap (PBG) — the inhibition of spontaneous emission of light from atoms and molecules. By analogy with electronic semiconductors, the periodicity of the underlying lattice of a PC should be of the same order of magnitude as the wavelength of the electromagnetic radiation.