Investigation on the smoothing of surface spatial frequency errors for borosilicate glass by heat-treatment

The mid-spatial frequency error and high-spatial frequency error on the optical glass component surface limit the development of high-power laser devices. By heat-treatment in wet atmosphere, the surface can be smoothed spontaneously under the action of capillary force, which is positive to improve the quality of optical components. In this paper, the finite element simulation model of the glass surface smoothing process is established based on the level-set method. The factors affecting the smoothing process, such as morphology wavelength and viscosity, are analyzed by simulation. A series of surface smoothing heat-treatment experiments for borosilicate glass were carried out to verify the effectiveness of improvement on surface quality through heat-treatment. Finally, the reasons for the discrepancy between theory and experiment are investigated through the simulation, and the effects of wavelength and the water content in the material are further investigated.