Optical components are key elements in modern optics and laser technology. In analogy to the resistors, capacitors or many other parts controlling the electron current in electronic circuits, they are needed to manipulate and control light in photonic circuits. For instance, no laser system could be operated without adapted mirrors forming a resonance cavity to store the light in the laser material until sufficient amplification is attained.

Typically, several hundred round trips have to be achieved for the photons to keep the system above the laser threshold. As a consequence, mirror reflectance values above 99 percent are often required. Such high values and many other optical functions can be achieved by optical interference coatings, which are formed by a stack of single transparent layers with different refractive indices. The new laser concepts and high precision measurement systems developed in QUEST impose extreme demands on the quality of interference coatings.

The research group on ultrahigh quality optical layers is dedicated to this needed new generation of optical coatings. Major targets are concentrated on the development of coatings with extremely high reflectivity above 99.9999 % and highest precision produced by ion beam sputtering (IBS). The research strategy of the group includes scientific objectives focused on a fundamental understanding and optimization of IBS-processes:

· Construction and implementation of an advanced ion beam sputtering system

· First approaches to modeling of ion beam sputtering processes and layer growth mechanisms

· Investigations in phase separated direct deposition processes and new approaches for a parametric control of the coating structure

· Improvement of deposition control techniques towards a precision on the atomic scale, development simulation algorithms for deposition control strategies

· Adaption of characterization techniques to the measurement of optical losses in the sup-ppm range

The research work is also oriented towards further applications in modern photonics addressing industrial companies in fields of precision optics and laser technology. On this basis, the research activities of the group could be strengthened by further research projects funded by the German Ministry of Research and Education (see for example Pluto: www.pluto-projekt.de).