Formation mechanism and suppression method of surface deterioration in CO2 laser polishing for fused silica

Thus, a double-side polishing method is proposed as a solution to suppress the scanning ripple and decrease roughness. Compared to single-side polishing, form error Root Mean Square (RMS) reduces from 0.433 λ (λ=632.8 nm) to 0.194 λ, and surface roughness decreases from 0.371 nm to 0.270 nm by double-side polishing with a power density of 4.244 kW/cm2 and a scanning speed of 1.3 mm/s. Plus, the laser-induced damage thresholds (LIDT) after double-side polishing at 0% and 100% probability demonstrated a marked improvement, rising from 19.4 J/cm² and 39.2 J/cm² to 21.2 J/cm² and 41.5 J/cm², respectively.

The enhancement of the form error, surface roughness and LIDT is attributed to the offset of residual thermal stress and secondary surface melting flow. This research provides valuable insights into enhancing the processing quality and performance of fused silica.