Anisotropic dependence of damage induced by femtosecond laser ablation on single-crystal calcium fluoride surfaces

Abstract The crystal plane dependence of femtosecond laser ablation of calcium fluoride single crystal was investigated. The results show that 90 ∘ orthogonal cracks are produced on the (100) plane, 72 ∘ inclined cracks are formed on the (110) plane, and 62 ∘ three-way cracks with irregular outward expansion appear on the (111) plane. The local transient stress field and stress intensity factor were calculated. The effective stress intensity factors all exceed the critical value of the material fracture toughness. The differences in crack lengths in different crystal directions are attributed to the coupling effect of crystal anisotropy and local stress field.