Benefits of ion milling ULE as compared to glass ceramics

J. F. Ellison; G. P. Cox; L. J. Sutton; A. C. Fox; T. M. Rich; T. A. Sebring

doi:10.1117/12.2023532

26 September 2013 Benefits of ion milling ULE as compared to glass ceramics

J. F. Ellison, G. P. Cox, L. J. Sutton, A. C. Fox, T. M. Rich, T. A. Sebring

Proceedings Volume 8860, UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts VI; 88600O (2013) https://doi.org/10.1117/12.2023532
Event: SPIE Optical Engineering + Applications, 2013, San Diego, California, United States

Abstract

Corning’s ULE^® is an ultra-low expansion glass used for machine tool blocks to astronomical mirrors. Its primary alternative is a glass ceramic. In many applications, ion beam milling is used for final surface figuring. Ion milling removes material at an atomic level and is typically a slow, expensive process. Experiments have determined the upper limits of removal rate for ion beam milling during optical figuring. The goal was to increase the power density of the ion beam during figuring to achieve higher removal rates with no negative effects on surface properties. Testing shows that the removal rate on ULE^® is about 50% higher than on glass ceramics under the same conditions. With an increase in material removal rate, both ULE^® and the glass ceramic show an increase in surface roughness. Average birefringence of both materials increases slightly after milling; however the level of birefringence in the glass ceramic is seven times larger than for ULE^®. Therefore using higher ion milling power densities, the surface figuring of ULE^® can be accelerated to produce shorter processing times without adverse effects on surface properties. This can help lower the cost for manufacture of ULE^® optics.

Citation Download Citation

J. F. Ellison, G. P. Cox, L. J. Sutton, A. C. Fox, T. M. Rich, and T. A. Sebring "Benefits of ion milling ULE as compared to glass ceramics", Proc. SPIE 8860, UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts VI, 88600O (26 September 2013); https://doi.org/10.1117/12.2023532

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