Hanjörg Wagner

Recent advancements in photonics have intensified the performance requirements for optical systems and present significant challenges for optical coating technologies. Conventional interference coating systems often prove to be insufficient, especially in applications requiring large angles of light incidence or a wide wavelength range. Nanostructures, which consist of an air material mixture, offer promising alternatives. In this work, silica nanostructures are manufactured by the AR-plas2 method, in which first an organic layer is evaporated onto a substrate. This organic layer forms self-organizing nanostructures by a plasma etching step, which are subsequently coated with silica. Finally, the organic residues are removed by additional plasma etching and heat treatment steps, which results in hollow silica structures. The work examines the optical and functional properties of these structures designed for 355 nm to demonstrate their use as anti-reflective coatings for advanced optical systems.

Stray-light reduction is critical for the operation of optical components in space. Here, we report on the testing of high performance plasmonic broadband absorbing black coatings for space applications fabricated by metastable atomic layer deposition (MS-ALD). For this purpose, humidity testing, thermal cycling, exposure to atomic oxygen, and adhesion testing were used as testing methods. The results show that the films with thickness greater than 9 μm are able to withstand the humidity tests, thermal cycling, and exposure to atomic oxygen without significant loss of their broadband absorption. However, it was also observed that the adhesion of the films has not yet been sufficient to meet the requirements posed by the space environment. Therefore, the authors conclude that further fine-tuning of the films with respect to increasing adhesion is required to make the films suitable for space applications. Therefore, the authors propose to investigate the coating of the MS-ALD films with high refractive index coatings.