Photonic crystals

Illustration 17: SEM

Images of two-dimensional photonic crystals. Scale of length (a) 10 ^m, (b-e) 1 ^m, (Source: Campbell et al. 2000)

Illustration 17: SEM

Images of two-dimensional photonic crystals. Scale of length (a) 10 ^m, (b-e) 1 ^m, (Source: Campbell et al. 2000)

Photonic crystals are a further example of nano-optoelectronic components with application potential in optical data communication. Photonic crystals exhibit a periodic refractive index and possess an analogy to semiconductors in electronics, a "photonic band gap" for certain frequency in the visible and IR wavelength ranges. The lattice constant of photonic crystals lies in the range of half the wavelength of the light in the medium. For visible light this means that for the production of photonic crystals a precision within the range of 10 nm is necessary. Two-dimensional structures today can be routinely manufactured with high precision. At present, intensified efforts are made for the development of three-dimensional photonic crystals, e.g. with utilization of lithography and self-organization procedures, in which nanoscale colloids (e.g. from polymers or silicates) arrange spontaneously to a cubic lattice. These lattices are used as templates for lattices from more interesting materials such as metals and metal oxides. Three-dimensional photonic crystals would open up new possibilities in optical data communication (light could be guided and branched to arbitrary directions) and offer in principle the potential for the realization of purely optical circuits (optical computing). Such photonic transistors are however at present still very far from realization (Yablonovic 2002). In the long run, photonic crystals will find applications in optical satellite communications.

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