The light modulation of scratches on the surface of fused silica glass

Surface defects of fused silica glass have become the main reason that limits the resistance of fused silica components to laser damage. When the laser enters the scratch, the scratch modulates the incident light field to increase the local light intensity, increase the probability of damage to the optical element, and reduce the damage threshold. In order to study the modulation effect of scratches on the light field, this paper considers radial triangular scratches and uses the finite difference time domain (FDTD) method to establish a laser incident triangular scratch model. As a result, with the increase of the scratch width w, the maximum light intensity enhancement factor (LIEF) on the front surface of the scratch is 4.6, and the maximum LIEF on the rear surface can reach 9.2. With the increase of the scratch depth d, the LIEF on the front surface of the scratch is 7.5, and the maximum LIEF on the rear surface can reach 12.2. When the scratch is located on the rear surface, the incident laser occurs totally reflection, the interference effect is obvious, the LIEF becomes larger, and the rear surface is more prone to damage.