Ion-beam methods for high-precision processing of optical surfaces

Methods for high-precision processing of surface of optical elements using beams of accelerated ions are considered. Characteristics and parameters of the equipment and problems that can be solved are presented. It is shown that final correction of local shape errors is possible with the aid of small-size ion beam and axisymmetric correction/aspherization is possible using wide-aperture ion beam and ion polishing. Effective roughnesses of the surfaces of fused silica, sitall, Zerodur, and ULE$\circledR$ are obtained at spatial frequencies of $q\in$ [2.5 $\times$ 10$^{-2}$–6.0 $\times$ 10$^{1}$ $\mu$m$^{-1}$]. Examples of aspheric surfaces and aspherization profile are presented.