SiC coatings on RB SiC mirrors for ultrasmooth surfaces

Steven G. Johnson

doi:10.1117/12.165233

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6 December 1993 SiC coatings on RB SiC mirrors for ultrasmooth surfaces

Steven G. Johnson

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Proceedings Volume 2018, Passive Materials for Optical Elements II; (1993) https://doi.org/10.1117/12.165233
Event: SPIE's 1993 International Symposium on Optics, Imaging, and Instrumentation, 1993, San Diego, CA, United States

Abstract

This is a review of the demonstrated capability to produce ultra-smooth super-polished surfaces (< 2 angstroms rms) when a reaction bonded silicon carbide (RB SiC) mirror is coated with a SiC coating. Also covered is the viability of this design choice for large scale lightweighted mirror blanks. A super-polished surface finish on bare RB SiC is not attainable due to the difference in hardness of the two phases, SiC and up to 30% silicon. Therefore, deposition of an additional layer of SiC onto the figured RB SiC blank is required. This technique has been demonstrated and can result in meter class optics with a surface roughness in the regime of less than 2 angstroms rms. The blank and optical fabrication techniques are described along with performance characterization data.

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Steven G. Johnson "SiC coatings on RB SiC mirrors for ultrasmooth surfaces", Proc. SPIE 2018, Passive Materials for Optical Elements II, (6 December 1993); https://doi.org/10.1117/12.165233

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