Stefan Bruns

Development of a broadband dielectric beam splitter with reduced spectral wavefront error

A broadband beam splitter coating with the reflecting range from 400 to 900 nm and the transmitting range from 920 to 2300 nm was developed. To avoid absorptive losses at low wavelengths, Ta2O5 was chosen as the high index material. A new setup based on a Hartmann-Shack sensor was built to measure the wavefront error and its spectral dependence. An area of 120 mm diameter was measured. While in a standard coating, large resonant-like wavefront errors occur, an optimized coating with significantly reduced spectral wavefront error was designed and produced.

Properties of Reactive Sputtered Alumina-Silica Mixtures

Standard antireflective coatings applied to hard substrates suffer from poor abrasion resistance. The properties of the low refractive index material silica can be modified by mixing with alumina by reactive magnetron sputtering on heated sapphire.

Recent results of optical coatings deposited on the EOSS coater

In 2011 an optical interference manufacturing platform called EOSS was presented by the Fraunhofer IST. This platform employs cylindrical cathodes in a special sputter-up configuration. The latest results obtained at this coater are presented.