Ion beam figuring of CVD silicon carbide mirrors

P. Gailly; J.-P. Collette; K. Fleury Frenette; C. Jamar

doi:10.1117/12.2308012

21 November 2017 Ion beam figuring of CVD silicon carbide mirrors

P. Gailly, J.-P. Collette, K. Fleury Frenette, C. Jamar

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Proceedings Volume 10568, International Conference on Space Optics — ICSO 2004; 105681G (2017) https://doi.org/10.1117/12.2308012
Event: International Conference on Space Optics 2004, 2004, Toulouse, France

Abstract

Optical and structural elements made of silicon carbide are increasingly found in space instruments. Chemical vapor deposited silicon carbide (CVD-SiC) is used as a reflective coating on SiC optics in reason of its good behavior under polishing. The advantage of applying ion beam figuring (IBF) to CVD-SiC over other surface figure-improving techniques is discussed herein. The results of an IBF sequence performed at the Centre Spatial de Liège on a 100 mm CVD-SiC mirror are reported. The process allowed to reduce the mirror surface errors from 243 nm to 13 nm rms . Beside the surface figure, roughness is another critical feature to consider in order to preserve the optical quality of CVD-SiC . Thus, experiments focusing on the evolution of roughness were performed in various ion beam etching conditions. The roughness of samples etched at different depths down to 3 ≠m was determined with an optical profilometer. These measurements emphasize the importance of selecting the right combination of gas and beam energy to keep roughness at a low level. Kaufman-type ion sources are generally used to perform IBF but the performance of an end-Hall ion source in figuring CVD-SiC mirrors was also evaluated in this study. In order to do so, ion beam etching profiles obtained with the end-Hall source on CVD-SiC were measured and used as a basis for IBF simulations.

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P. Gailly, J.-P. Collette, K. Fleury Frenette, and C. Jamar "Ion beam figuring of CVD silicon carbide mirrors", Proc. SPIE 10568, International Conference on Space Optics — ICSO 2004, 105681G (21 November 2017); https://doi.org/10.1117/12.2308012

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