Procedures are described to figure optical surfaces by ion polishing. Fused silica, ULE, and Cer-Vit were employed as substrate materials. The sputtering yields for these materials were: 1.9 (150-keV40 Ar+), 1.86 (150-keV 40Ar+), and 3.7 (80-keV 126Xe+) atoms/ion, respectively. The optical scatter, at λ = 632.8 nm, was measured to be 0.06%, which is comparable to good surfaces prepared by conventional lap techniques. The rms surface error was reduced from 0.05λ to 0.01λ over the central 0.12-m aperture of a 0.2-m diam fused silica flat by ion polishing with 150-keV 40Ar+. Based on this experience, the design of a manufacturing facility is discussed.
J. B. Schroeder, H. D. Dieselman, and J. W. Douglass, "Technical Feasibility of Figuring Optical Surfaces by Ion Polishing," Appl. Opt. 10, 295-299 (1971)