Investigation of stress during 3.8 μm laser mitigating damage growth on fused silica

The residual stress following mid-to-far infrared laser mitigation of fused silica damage results in crack growth and reduces the lifetime of fused silica. Understanding the evolution of stress during laser mitigation is essential for advancing laser repair technologies. In this study, an experimental setup was established to measure the real-time stress distribution during 3.8 μm mid-infrared laser irradiation, aiming at mitigating damage growth on fused silica. The experimental results indicate that the evolution of the principal stress can be divided into three distinct stages based on the state of the material. After the material was heated and melted, the principal stress distribution could be classified further into three directional layers. Additionally, a mechanical model of the interaction between the 3.8 μm laser and fused silica was developed to investigate the depth-dependent stress distribution during mitigation. The simulation results demonstrated that the maximum principal stress was consistently compressive, with a larger compressive stress occurring inside the fused silica.