Structural design and simulation analysis for plasma edge diffusion control in diamond polishing

Ion beam etching technology demonstrates unique advantages in sub-nanometer-level surface shaping and microstructure fabrication of diamond optical components due to its non-contact machining characteristics, particularly enabling ultra-smooth processing of precision devices like diamond cutting tools, complex curved lenses, and diffractive optical elements. However, disordered plasma diffusion during non-etching phases induces secondary contamination in the reaction chamber, increasing diamond surface defect density and degrading its light transmittance. To address this, the study proposes a "guidance + suction + passivation" triple control mechanism, which precisely constrains plasma pathways via multi-physics field coupling. Specifically, this mechanism integrates a fluid dynamics-optimized annular guidance channel (curvature radius R=50 mm) to direct plasma migration and an L-shaped vacuum suction system to minimize residual plasma accumulation, collectively suppressing plasma density fluctuations to within ±5%. Paired with a lattice passivation approach—applying a CVD-SiC/ AlN composite coating to the diamond surface—this strategy effectively suppresses subsurface carbon-based particle redeposition and enhances surface quality. Experimental results show this integrated method significantly reduces etching-induced defects, improving both the optical performance of diamond components and the reliability of atomic-level precision processing for high-refractive-index lenses and ultra-hard tools.