Effects of different kinds of mitigated pits on transport of laser beam

According to the different kinds of morphology features, 3D grid models of mitigated pits were built, and effects of different kinds of mitigated pits models on transport of laser beam (351 nm) was studied by using scalar diffraction theory and Fast Fourier Transform (FFT) methods. The results indicate that the off-axis downstream intensification of different kinds of mitigated pits, including conic, parabolic and Gaussian, pits, mainly relies on the depth of the mitigated pit. For the off-axis intensification, the maximum intensity increases with deepening depth, and the location of the maximum intensity approaches the output surface of optics with increasing pit depth, and is far away from the output surface of optics with the increasing diameter of mitigated pits. In addition, when the depth and diameter of different kinds of mitigation pits are equal, the parabolic mitigated pits can be the best choice for mitigated morphology. The results of this research indicate that the downstream intensification, which is induced by the mitigated damage pits, can be suppressed by controlling the morphology features of mitigated pits.