Information A microstructured material is one that is structured on the scale of the optical wavelength. A diffraction grating is a simple example. Another distinction is that we are in principle free to engineer the structure of a photonic crystal as we please, limited only by the available microfabrication technologies. An SEM image of a photonic crystal fibre. The fibre is about 40 microns across.
Light can behave in unfamiliar ways in a photonic crystal.
For example, constructive multiple-beam interference in the periodic structure can expel light from the material for certain frequencies and directions of incidence. It can be possible for light of certain frequencies to be expelled for all directions - light of these frequencies simply will not propagate in the material. A photograph of the far field pattern emerging from a photonic crystal fibre. The fibre was carrying red light from a helium-neon laser and green light from an argon ion laser. In practice, it is extremely difficult to make three-dimensional photonic crystals on the scale of a micron.