Influence of parameters on the surface roughness of the CO2 laser polished fused silica glass

Abstract

The laser polishing method has the advantages of high efficiency and no impurity doping. In this paper, the CO2 laser is used to polish the fused silica glasses. The optimized parameters of the CO2 laser are obtained by adjusting scanning speed, duty ratio, frequency, and defocus amount. The polishing times, track pitch and circumference, and initial roughness of the silica samples are studied. The process parameters have a different influence on the roughness of the polished samples. The results show that lower surface roughness can be obtained in line polishing when the power density is close to the evaporation threshold. The surface roughness of the silica sample is reduced by a low heat with multiple polishing. The lower the initial roughness of silica sample, the lower the surface’s roughness is after polished. The lowest surface roughness Ra = 0.22 µm is obtained, and the process parameters are selected: scanning speed 100 mm/s, frequency 15 kHz, duty ratio 50%, defocus +6 mm, track pitch 0.01 mm, unidirectional scan path length 40 mm width 36 mm. When the process parameters are the same and the roughness of multiple line polishing is the same as the roughness of area polishing, the relationship between the ratio of channel width and the number of polishing times in line polishing is equal to the track pitch during area polishing. The influence of track circumference on the roughness can be negligible.