Theoretical and experimental study on plasma-induced atom-migration manufacturing (PAMM) of glass

Abstract

Optical manufacturing plays an important role in various fields, such as optical lenses, telescopes, and laser optics. Generally, traditional optical manufacturing techniques are all subtractive processes based on the micro-shearing effect between the tool and surface protrusions. This paper reports a plasma-induced atom migration manufacturing (PAMM) process, which is a nonsubtractive finishing approach by which angstrom level surface roughness of fused silica has been successfully achieved. Inductively coupled plasma (ICP), which is characterized by high temperature and high radical density, is used as the tool of PAMM. After obtaining instantaneous plasma energy input on the fused silica surface, the peak site atoms migrate to the valley sites, thereby reducing the roughness. According to the energy minimization principle, this migration process continues until an ultra-smooth surface with reduced surface energy is formed. Atomic-scale molecular dynamics simulations were performed to clarify the microscopic mechanisms of PAMM, and experiments were conducted to verify its smoothing capability. The roughness of a ground silica surface was drastically reduced from Sa 391 nm to Sa 0.16 nm. This study demonstrates the feasibility of the PAMM as an alternative approach for atomic-level surface manufacturing.