Photonic crystals

The invention relates to photonic crystals, i.e. three-dimensional dielectric structures which are opaque to electromagnetic radiation within a given wavelength irrespective of the direction of incidence. An inventive photonic crystal comprises, for instance, a matrix-type arrangement of free-standing dielectric micro-columns or cylinders having small diameters. Said micro-columns or cylinders are placed on a substrate whose thermal expansion coefficient between 60° C. and 85° C. is at least 50% lower than the thermal expansion coefficients of quartz glass, thereby enabling the thermal expansion of the substrate to be kept to a minimum even when high termperature variations occur; whereby the distance between the micro-columns supported by the substrate or the microcylinders of the photonic crystal varies only to a small amount, whereby the optical characteristics are essentially more stable than those of photonic crystals with a quartz glass substrate. Preferably, glass ceramics or, for example, Zerodur® are used as a substrate.