Atomic-level surface planarization of fused silica by GCIB bombardment.

Atomic-level planarization of fused silica is critical to make precision optical components with ultra-smooth surfaces in high-intensity laser systems. This study demonstrates a method to make the fused silica surface an atomic-level surface planarization based on gas cluster bombardment by simulations. In this work, the surface planarization effects of a polished fused silica under varying cluster energies, sizes, and incident angles were investigated. The results show that the gas cluster bombardment by a grazing incidence can achieve an optimal planarization when the energy per atom (E/N) in the cluster is about the Si-O binding energy. In this case, the cluster bombardment under a proper dose can make the surface roughness Rq reduce to approximately 0.28 nm. Meanwhile, the short-wave (2-40 nm) roughness can be suppressed by about five times. This result could be useful for surface post-polishing treatment of fused silica, with applications in high-power laser systems for manufacturing ultra-smooth optical components.