Figure Correction of a Quartz Sub-Mirror for a Transmissive Diffractive Segmented Telescope by Reactive Ion Figuring

A quartz sub-mirror was figure-corrected in a parallel removal process for the first time. An Reactive Ion Figuring (RIF) process with a simple and universal masking method was demonstrated, and the 350-mm quartz sub-mirror was figure-corrected from the initial figure error of ~23 nm RMS to the final figure error of ~8 nm RMS in total effective figuring time of ~52 minutes after 4 iterations, which exhibited the actual potential of RIF on the figure-correction of quartz optical elements and the possibility on applying RIF to meet the requirement of mass production for sub-mirrors of transmissive diffractive segmented telescopes.