Where "defects" are desired – photonic crystals

Fig. 1: SEM image of a photonic crystal, fabricated using femtosecond lasers

A new research project at the Laser Zentrum Hannover e.V. (LZH), which is supported by the European Union, aims at making possible the production of nanooptical components, mainly photonic crystals, using laser technology. Such components can be used in particular in highly integrated systems of optical signal processing.

The principle of photonic crystals is to specifically control or suppress the propagation of light by so-called “defects”. Simple optical functions can be realized by systematically arranging a large number of defects. One important advantage of this technology is that a great many optical functions can be integrated into a very small volume of only a few cubic millimeters. This allows also complex optical systems to be realized, for instance for future optical information processing.

For the fabrication of such optical elements, construction platforms made of nanoscale polymers are developed in the project. They get their optical functionality by a downstream laser process. Using high-resolution femtosecond lasers, first some areas of the polymer structure are modified, from which the defects are then developed in the following process steps. The exact position of and link between the individual defects to form a functioning optical system is previously determined by novel simulation tools, specifically developed for this procedure.

In this research project, supported by the European Union, the LZH, in cooperation with five other European partners [BASF AG (D), Thales (F), TU Denmark (DK), PhotonDesign (UK), ENSTB (F)], intends to develop process and material technologies which allow a fast and flexible fabrication of three-dimensional photonic crystals. At the same time, the simulation and design tools shall also be optimized. The first projected structures are waveguides and filters for applications in telecommunication. Already now it is estimated that photonic crystals could play the same part in optical information processing as do semiconductors and chips in present computer technology.

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Michael Botts
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The Laser Zentrum Hannover e.V. (LZH) carries out research and development in the field of laser technology and is supported by the Ministry of Economic Affairs, Labour and Transport of the State of Lower Saxony (Niedersächsisches Ministerium für Wirtschaft, Arbeit und Verkehr).