Improvement of polishing properties of different mirror materials by pulsed laser deposition of brittle hard ceramic thin films

As part of the UCM4Space project (ultralight Carbon Fiber Reinforced Plastic (CFRP) mirrors for space telescopes), an improvement of the polishing properties of CFRP and other materials is developed to get to roughnesses below 1 nm. For this purpose, CFRP samples, pure epoxy resin samples and ceramic samples made of Carbon fiber reinforced SiC (HB-CESIC) with a microroughness of less than 10 nm RMS were received. Alumina (Al2O3) was then successfully deposited on the 60 mm diameter samples via Pulsed Laser Deposition (PLD). Measurements with an AFM, SEM and a white light interferometer showed no change of the microroughness and the geometry of the surface grooves before and after the coating. It can be concluded that the PLD coatings make a direct copy of the sample surfaces. The adhesion between the ceramic layer and the tested materials was also found to be promising for a post-polishing step.