A novel finishing method of the precision optics using a gas cluster ion beam

As the high quality and ultra-precision optical surface are significantly required, the optical polishing and finishing techniques have been developed. Ion beam figuring (IBF) has been used as a powerful tool for correcting errors on an optical surface at sub-nanometer level. A gas cluster ion beam (GCIB) is the ion beam etching method with extremely low energy per atom, which is used for the sputtering or the depth profiling of a secondary ion mass spectrometry (SIMS). In this study, GCIB was applied to the finishing process for the precision optics. To demonstrate this technique, we optimized the GCIB parameters such as the acceleration voltage and the dwell time. We also measured the roughness profile using coherence correlation interferometry (CCI) to compared before and after the processing. Here, we will discuss the effect of the GCIB processing on the roughness and the possibility of this method for precision optics.