Research On Femtosecond Laser Spatially Shaping Bessel Beam Processing Three-dimensional Surface With Antireflection Performance

With the development of advanced manufacturing and processing technologies,it was difficult to realize fine processing on complex three-dimensional curved surface until now it can realize curved surface processing through various means.The number of products with complex curved surfaces has also been greatly developed.These products are widely used in shipbuilding,aviation,energy and other applications.Many traditional methods are used to process three-dimensional curved surfaces such as mechanical processing,photolithography and the like.However,these traditional processing methods have the disadvantages of complicated processing process,high equipment cost,and pollution to the environment when processing three-dimensional curved surfaces.The femtosecond laser can process high-precision precision micro/nano structures on three-dimensional surfaces with its processing characteristics.However,the commonly used femtosecond laser three-dimensional curved surface processing methods have certain defects during the processing.The femtosecond laser filament processing method is mainly limited by the energy of the laser,and requires a high peak power of the laser;the femtosecond laser confocal system method needs to perform a profile scan first,and then realize three-dimensional curved surface processing according to the profile information,the processing efficiency is limited in this method;femtosecond laser galvanometric scanning system methods also include topographic mapping,so the processing efficiency is also limited;the method of using spatial light modulators(SLM)to control the intensity distribution after focusing is very complex in terms of algorithm,and this drawback causes this method to be unfavorable for large-area processing.By spatially shaping a Gaussian beam into a Bessel beam with an axicon,which has the advantage of ultralong focal depth,so Bessel beam is very suitable for the three-dimensional curved surface processing.At the same time,the existing antireflection surface is mainly manufactured in a one-dimensional plane.The three-dimensional curved surface with antireflection performance obtained by this method has a larger surface area for absorption than a one-dimensional plane,and has been improved in terms of energy efficiency.In this paper,femtosecond laser Bessel beams are used to fabricate micro/nano structures on copper materials with three-dimensional curved surfaces,and then thermal oxidation is used to obtain functional surfaces with antireflection properties.The specific research content is as follows:1.Theoretically analyze the expression of the intensity of Bessel beam produced by the axicon;using Matlab software to simulate the intensity distribution of Bessel beam in the Z-axis and cross-section,and the beam quality meter is used to test the Bessel beam generated by the axicon.2.Using the telescope system to increase the energy density of Bessel beam,change the thermal oxidation temperature to obtain the suitable temperature,and ablate the copper material surface by adjusting the laser energy and scanning speed to get gully structure.The flat sample was placed in different positions in the direction of the Bessel beam propagation to prove the Bezier beam 3D surface processing capability(the Z-axis processable range is4000?m),combined with thermal oxidation to obtain a surface with excellent antireflection performance.Finally,the actual processing on a three-dimensional surface of a copper ball was performed and the morphology was characterized using a scanning electron microscope.3.The femtosecond laser Bessel beam produced by spatial shaping of an axicon is directly used in the three-dimensional curved surface processing to induce a Ripple structure on the surface of the material,and the theoretical formula of the femtosecond laser induced surface periodic structure is summarized.The parameters of the laser energy and scanning speed were adjusted to induce a regular Ripple structure on the surface of the copper material.The planar sample was placed at different positions in the Bessel beam propagation direction to demonstrate the three-dimensional curved surface processing capability of Bessel beam(The Z-axis processable range is 20000?m),combined with thermal oxidation and testing its surface reflectance to obtain a surface with excellent antireflection performance.After the telephoto system was not used,the three-dimensional curved surface processing capability was greatly improved.Finally,actual processing was performed on a curved copper sheet with a three-dimensional curved surface to confirm the Bessel beam three-dimensional surface processing capability.