Newsletter of the Fraunhofer IST

Dear reader,

In mid-summer temperatures just before the start of the holiday season, we are pleased to send you our second newsletter of 2019. We would also like to cordially invite you to visit us at the LASER World of Photonics. From the 24^th to the 27^th of June we will present our latest developments in the field of precision optics at a joint Fraunhofer booth. In addition we would like to draw your attention to our annual report of 2018. 

In this newsletter in the column “answers“, you will find the continuation of Professor Bräuer's answer to the question about the creation of a vacuum. By the way: If you always wanted to pose your own question concerning our research topics, please do not hesitate to contact us.

We hope you enjoy reading our latest reports and wish you a wonderful summer to recharge your batteries ready for a successful second half year.

The Editorial Team

Optical functions – e. g. anti-reflective coatings or filters for specific spectral ranges – can be realized by means of interference coating systems. These systems deploy a sequence of high and low-refractive layers (e. g. Ta₂O₅ und SiO₂) whose layer thicknesses are precalculated according to the desired optical function. At the Fraunhofer IST, such coating systems are produced by means of magnetron cathode sputtering; applications are optical components in the field of precision optics.

In order to minimize the quantity of optical components – and, thereby, disturbing reflections - interference coating systems should be applied directly to curved lens surfaces. As a result of the differing angles of incidence at different impact points, the wavelength range of the optical functional layers shifts. The compensation of this effect requires a precisely conformed layer-thickness profile.

For the realization of these requirements, the Fraunhofer IST developed the simulation software MOCCA^+® for magnetron cathode sputtering, with which plasma discharge, gas dynamics and the dynamic coating of moving 3D components can be simulated. With the aid of this simulation environment, a process for applying interference coating systems to convex lenses was developed. A lens coated with a bandpass filter served as the demonstrator, in which the transmission band always remains within the same wavelength range irrespective of the position of the incident light. In the future, the simulation-based process will be extended to other component geometries, thereby enabling the realization of precision optical coatings in a multitude of applications.