Optical & Photonic QuasiCrystals
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Photonic Crystals
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The study of the physical and optical properties of photonic crystals has generated
a burst of new ideas for optical devices and systems.
Special mention needs to be made here of photonic crystal silica fibres, which appear as the first application of photonic crystals to the real world of optical communications. In the field of semiconductors and metals, the fabrication of photonic crystals has represented an important challenge for micro- and nanotechnology. In turn, these technologies have benefited from the validation of processes which has thus been completed. In this respect, the evolution of photonics has paralleled the revolution which has been taking place in the field of electronics with the development of nanotransistors and quantum dot memories. Nanophotonics are now being recognized as a special branch of optics, in much the same way as nanoelectronics form a special branch of electronics. Some of the technological problems that had appeared at the time of the first studies on photonic crystals, are currently in the process of being solved. However, it should be stressed that future development and applications of photonic crystals are definitively dependent on the degree of accuracy which can be achieved in the fabrication of micro- and nanostructures, and thus on the overall dimensions of the corresponding devices. One of the most striking illustrations of the fruitfulness of research on metallo-dielectric photonic crystals is probably the development of the so-called metamaterials, which are expected to provide a new approach towards negative refraction, through the simultaneous control of the effective permittivity and the effective permeability. |
Photonic Quaicrystals
A very simple method for constructing quasi-crystals is represented in Fig. 3.1. This method consists in projecting a structure exhibiting a periodicity in an Ndimensional space onto a space of lower dimensionality. The structure considered here is a grid G with a square symmetry. A one-dimensional quasi-crystal can be derived from the grid G by considering all intersections of this grid with a straight line ? of irrational slope. The intersection points thus generated are indeed distributed according to a quasi-periodic pattern. In practice, a photonic quasi-crystal can be constructed by alternately stacking dielectric layers with permittivities e1 and e2 respectively, in such a way that the thickness of the layers will vary with the distance between the successive intersection points represented in Fig. 3.1. Under ConstructionI will be doing an entire section on photon logic and the basic designs behind photonic circuits. |
