Physics / mechanism
Ion-beam figuring (IBF) uses a low-energy, broad noble-gas ion beam (typically Ar or Xe, 300–1500 eV) directed at an optical surface to remove material atom-by-atom via momentum-transfer sputtering. The removal function is deterministic and Gaussian-shaped; iterative dwell-time algorithms (derived from deconvolution of the tool influence function) converge surface figure error toward sub-nm RMS. No tool contact means no subsurface damage and no mid-spatial-frequency polishing artifacts introduced. State-of-the-art IBF systems (Zeiss, Optically Driven Figuring/Tinsley, SORL) achieve λ/50 figure accuracy at 632 nm, surface roughness <0.1 nm RMS, and are production-qualified for EUV lithography optics, space telescope mirrors, and X-ray synchrotron optics.
Competitive landscape
Adjacent finishing techniques compete across different error-spatial-frequency regimes. Magnetorheological finishing (MRF) handles mid-spatial frequencies faster but introduces residual iron contamination and struggles below 1 nm RMS. Reactive-ion etching (RIE) planarizes at wafer scale but lacks freeform figure control. Subaperture lap polishing remains cheaper for loose tolerances. IBF has no peers for combining freeform geometry, angstrom-level figure, and zero mechanical stress delivery.
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.