a material that contains a periodic arrangement of air-filled voids that have a lower refractive index than the host material
a (non-existing so far) periodic dielectric medium that is an optical analog of semiconductors
a periodic dielectric structure with a band gap that forbids propagation of a certain frequency range of light, enabling one to control light with impressive facility
a structure having a periodic variation in permittivity (dielectric constant)
Photonic crystals are made up of a regular crystal lattice of a material that is embedded in another material with very different refraction properties. Photonic crystals do not allow light propagation for certain light wave lengths (bandgap). This property is similar to that of the semi-conductors used in computer chips. In semi-conductors, electrons are also limited in their movement by a bandgap. But it is exactly this that makes for the enormous potential of semi-conductors in electronics.
The optical analog of semiconductor crystals.
Photonic crystals are periodic optical (nano)structures that are designed to affect the motion of photons in a similar way that periodicity of a semiconductor crystal affects the motion of electrons. Photonic crystals occur in nature and in various forms have been studied by science for the last 100 years.
