Elastic Emission Machining of Substrates for EUV, Optical, and Infrared Optics

Diffraction limited, low cost, and low weight mirror systems are required to enable and enhance telescopes for missions of all sizes, from CubeSats to Flagship missions. These missions also vary in their operating wavelengths from ultraviolet to far-infrared. With this wide range of sizes and operating wavelengths, a solution that is applicable to any size and material is necessary, capable of the following performance goals:Mid-spatial frequency errors (6 ndash; 60 cycles per aperture (CPA)) lt;5nm RMSHigh-spatial frequency errors (gt;60 CPA) lt;1.5 nm RMSMicro-roughness lt;0.5nm RMSA methodology that OptiPro has recently employed can achieve these tolerances and is scalable for any size of optic: Elastic Emission Machining. EEM is a chemical polishing method, which causes low-energy collisions to occur between particulates and a substrate. These collisions cause chemical reactions whereby the particles become chemically to the surface atoms. The fluid, in which the particles are immersed, is accelerated to flow, and produces a sheering force on the bound particle, which pulls it ndash; and its attached substrate atom ndash; from the substrate, producing an atomic-level machining operation. This process does not damage the atomic lattice structure, allowing for no sub-surface damage. With the material being removed from the surface by the particulate, a Beilby layer is not allowed to form over the optical surface. This technology has been demonstrated on Silicon, and during this Phase I we will demonstrate the process on Ultra Low Expansion glass (Corning Incorporated) and Zerodur (Schott AG).The other aspect of this project which OptiPro will demonstrate is the mitigation of mirror support print through on light-weighted mirrors. Support print through is a problem with light-weighted mirrors where the support structures are apparent in the mirror surface, due to a few factors which we believe EEM could solve, with its highly stable removal rates and low force for polishing.