Manipulation Of The Vectorial Field And Its Application In Surface Machining

Since the first laser was invented in 1960,human beings have started to manipulate the quality of laser in order to make better use of it.In this paper,the introduction gives the background of the vectorial optical field,including its concept,mathematical and physical basis and application in focusing.The physical mechanism of laser processing are summarized and the convenience and advantages of vector optical field in laser processing are analyzed.Secondly,the generation and modulation of vectorial optical field are introduced.The widely used generation methods are analyzed according to the active and the passive generation method,including the methods using space light modulator,Sagnac interferometer,meta-surface and so on.Based on the research background above,this paper studies the manipulation of vectorial fields and its application in surface machining.And the research contents and results are summarized below1、 In the third chapter,according to the application requirement of vectorial optical field in laser processing,the generation and modulation of super-long three-dimensional flat-top focusing light field under lower numerical aperture(NA=0.6)are studied.Utilizing the diffraction integral theory of vectorial fields and method of reversal construction of dipole-array radiation,the ultra-long depth of focus(>10λ)and the pattern of vectorial light field at pupil plane are obtained.The distribution parameters of light field can be used to design three-ring complex-amplitude pupil filter.Ultra-long three-dimensional flat-top focusing field can improve the processing efficiency and quality and the laser material processing and machining can benefit from this work.2、 In the fourth chapter,the experimental system for generating and manipulating vectorial field is set up.Utilizing this system,the surface machining on titanium alloy and silicon is studied.The effects of pulse energy,pulse number,polarization state and topological charge on the quality of holes are investigated by single factor variable method.The corresponding conclusions are obtained by scanning electron microscopy(SEM)analysis of the samples.The results show that the number of pulses and the energy of pulses have great influence on the depth and aperture of the hole.For the radially and azimuthally polarized light,the processing effect is better than that for linearly polarized light.The bottom of the hole processed by radially polarized light is smoother than that by azimuthally polarized light.When the number of topological charges does not exceed 4,the more the topological charges of the light,the smoother the bottom of the hole is.The debris around the hole is also less.These experimental conclusions are helpful for surface machining.