Near-field modulated simulation of repaired site contained crack or bubble in fused silica subsurface
裂纹或气泡对熔石英损伤修复坑场调制的近场模拟

Three-dimensional(3D) model of Gaussian repaired site contained crack or bubble is establishd,and 3D finite-difference timedomain method is used to simulate near-field modulation of 355 nm laser incidence by those defects on fused silica rear-surface.The results show that we should avoid any unrepaired cracks,especially cracks with incident angle of 65°,and the size of bubbles should be less than 5 A.All of the above can contribute to the weakening of the modulation around repaired pit.When crack or bubble distributes in the near-surface area(< 3λ) and close to the edge of pit ring,the field modulation is obvious.With the increasing of lateral gap, there will be a maximum due to electric field fluctuations near the surface area,especially when cracks are contained.And the electric field gradually stabilized when lateral gap is far from the surface.As the vertical gap increases,the number of large electric field grid points decreases,and stabilized oscillation emerges when vertical gap is larger than 3 A.If cracks or bubbles are located below Gauss repaired sites within a few wavelengths,its depth seems to be enlarged under irradiation.