Adjustment of Stress Induced by Ultrafast Laser Modified Silica Glass in Burst Mode

During the process of ultrafast laser modification of silica glass, the focal spot typically exhibits a strong central area and a weaker periphery. Furthermore, due to the plasma shielding effect, pulse energy cannot be effectively transferred into the silica glass, which makes it challenging to accurately predict the stress generated during the laser modification process. This study investigates the ultrafast laser energy modification of silica glass through both simulations and experiments, determining the stress distribution both during and after the laser processing. A single pulse is temporally modulated into burst pulses for processing silica glass, and the functional relationship between stress values and laser parameters (pulse energy and the number of sub-pulses in burst mode) is established. The modified silica glass is then subjected to wet etching to reduce or eliminate the residual stress, and a functional relationship is developed to describe the process. The silica glass pendulum was successfully fabricated by using the proposed technology in this study, with its overall maximum stress value precisely controlled to ensure it does not exceed 35.8 kPa.