Design and simulation of axial super-resolved phase plate in femtosecond laser microfabrication

In order to improve the quality of laser micromachining, the focal spot should be shaped. The Fresnel diffraction formula was analyzed, two kinds of axial super-resolved phase plates were designed by using Matlab based on genetic algorithms and design constraints. The normalized radiuses of 0. structure phase plate of four-ring are r1=0.15、r2=0.70、r3=0.81, and the normalized radiuses of non.0. structure phase plate of four-ring are r1=0.25、r2= 0.498、r3=0.652, the phases of each ring from the inside to the outside are 2.879、3.087、0、3.012. The longitudinal spot sizes after using the two phase plates are compressible to 76% and 75% of the Airy pattern , the ratios of the peak energy are respectively 0.39 and 0.42, and sidelobe energy are respectively 0.64 and 0.41.Two phase plates can be applied in femtosecond laser microfabrication.