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Proceedings Paper

Silicon carbide high performance optics: a cost-effective, flexible fabrication process
Author(s): John M. Casstevens; Abuagela Rashed; Ronald Plummer; Don Bray; Rob L. Gates; Edgar Lara-Curzio; Matt K. Ferber; Tim Kirkland
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Paper Abstract

Silicon carbide may well be the best known material for the manufacture of high performance optical components. This material offers many advantages over glasses and metals that have historically been used in high performance optical systems. A combination of extremely high specific stiffness (E/r), high thermal conductivity and outstanding dimensional stability make silicon carbide superior overall to beryllium and low-expansion glass ceramics. A major impediment to wide use of silicon carbide in optical systems has been the cost associated with preliminary shaping and final finishing of silicon carbide. Because silicon carbide is an extremely hard and strong material, precision machining can only be done with expensive diamond tooling on very stiff high quality machine tools. Near-net-shape slip casting of silicon carbide can greatly reduce the cost of silicon carbide mirror substrates but this process still requires significant diamond grinding of the cast components. The process described here begins by machining the component from all special type of graphite. This graphite can rapidly be machined with conventional multi-axis CNC machine tools to achieve any level of complexity and lightweighting required. The graphite is then directly converted completely to silicon carbide with very small and very predictable dimensional change. After conversion to silicon carbide the optical surface is coated with very fine grain CVD silicon carbide which is easily polished to extreme smoothness. Details of the fabrication process are described and photos and performance specifications of an eight-inch elliptical demonstration mirror are provided.

Paper Details

Date Published: 27 December 2001
PDF: 10 pages
Proc. SPIE 4451, Optical Manufacturing and Testing IV, (27 December 2001); doi: 10.1117/12.453653
Show Author Affiliations
John M. Casstevens, Dallas Optical Systems, Inc. (United States)
Abuagela Rashed, Poco Graphite, Inc. (United States)
Ronald Plummer, Poco Graphite, Inc. (United States)
Don Bray, Poco Graphite, Inc. (United States)
Rob L. Gates, Poco Graphite, Inc. (United States)
Edgar Lara-Curzio, Oak Ridge National Lab. (United States)
Matt K. Ferber, Oak Ridge National Lab. (United States)
Tim Kirkland, Oak Ridge National Lab. (United States)

Published in SPIE Proceedings Vol. 4451:
Optical Manufacturing and Testing IV
H. Philip Stahl, Editor(s)

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