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The surface quality of the optical element substrate will affect the laser damage threshold of the dielectric coatings. Substrate surface scratches are one of the common damages to the substrate. In this work, the parabola-section-model lateral scratches of the 45° HR coating with a central wavelength of 1064 nm substrate are studied, and the scratches and multilayer coatings are established. The three-dimensional finite element method is used to simulate the electric field modulation generated by scratches in the fundamental frequency high-reflective film when coatings irradiated at 1064nm and 355nm . The results show that under the same conditions, greater light intensification at the shorter wavelength.The electric field enhancement of p-polarized light is larger than that of s-polarized light. For 1064nm laser, when the incident angle is 45° The electric field intensity is the highest. When the incident laser at 355nm , the maximum intensity enhancement is produced when the incident is 60à.When the laser is incident at 45°, the greater the depth of the scratch, the stronger the electric field intensity in the film. The angle at which the 355nm laser is irradiated on the surface of the recessed film determines the magnitude of the electric field enhancement. Therefore, the electric field strength is very sensitive to the angle of incidence and the depth of the scratch.
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