增加飞秒激光光束焦深的折衍混合元件的设计制作
发布时间：2018-08-19 15:43
【摘要】：相比于长脉冲激光,飞秒激光具有的阈值效应明显、热影响区极小、重铸层极小、可控性高等特性,使其在微细加工中占有极其重要的地位。而其出射光束的焦深与焦斑则会直接影响到加工精度。在传统光学中,焦深和焦斑相互制约,无法在增加焦深的同时实现焦斑的不扩散。本论文选取折衍混合元件来增加飞秒激光光束的焦深,并从理论分析、计算仿真模拟、加工制作、测试四个方面具体介绍了该折衍混合元件的设计制作测试过程,主要研究内容如下:首先,通过理论分析和计算模拟得到折衍混合元件的面型参数。折衍混合元件的设计思路遵循改进的能量守恒法。根据Legend Elite飞秒激光器出射光束的参数特点和设计目标,确定折衍混合元件的基本参数;结合菲涅尔衍射理论,用MATLAB#174;编写折衍混合元件衍射面初始相位的计算程序并得到该元件衍射面型的初始相位矩阵,然后通过数据拟合得到衍射面归一化径向孔径坐标的系数值;在Zemax#174;中优化该元件衍射面型结构和折射面型结构,从而得到折衍混合元件的最终结构参数:选取BK7玻璃作为透镜材料;元件整体直径为20.000mm;衍射面直径为11.611mm;中心厚度为2.004mm;凸面曲率为66.542mm;有效焦距为95.257mm。二元面归一化径向孔径坐标的偶次幂系数值分别为:-377.347、335.116、-1174.462、544.835、-130.274。同时模拟分析了该折衍混合元件增加焦深效果,理论上可以使飞秒激光光束的焦深增加至1.5mm左右,焦斑直径大小为45.722μm左右。其次,对折衍混合元件进行制作。选用传统的套刻方法制作折衍混合元件的衍射微结构面。根据二元光学理论,计算元件各项加工数据,使用L-edit#174;软件绘制掩模版,经过光刻实验、等离子体刻蚀实验,制作完成折衍混合元件的衍射微结构面。在衍射微结构面制作完成后,对元件的另一面进行曲面加工,得到最终的折衍混合元件。最后,测试折衍混合元件的效果。使用显微镜、三维形貌仪观察元件形貌。在PMMA材料上测试元件增加焦深水平、出射焦斑大小。测试得到设计制作的折衍混合元件可以将飞秒激光光束的焦深增加到1.5mm左右,在PMMA材料上微孔的直径在100μm左右,符合飞秒激光微加工的要求。
[Abstract]:Compared with the long pulse laser, femtosecond laser has obvious threshold effect, the heat affected zone is very small, the recast layer is very small, and has a high controllability, which makes it play an extremely important role in micro fabrication. The focal depth and focal spot of the outgoing beam will directly affect the machining accuracy. In traditional optics, the focal depth and the focal spot restrict each other, so that the focal spot can not be diffused while increasing the focal depth. In this paper, the refractive-diffractive mixing element is selected to increase the focal depth of femtosecond laser beam, and the design and test process of the hybrid element is introduced from four aspects: theoretical analysis, simulation, fabrication and testing. The main contents are as follows: firstly, the surface parameters of the hybrid element are obtained by theoretical analysis and simulation. The design of the hybrid element follows the improved energy conservation method. According to the characteristic of Legend Elite femtosecond laser output beam and the design goal, the basic parameters of refractive-diffractive mixing element are determined, and the Fresnel diffraction theory is combined with Fresnel diffraction theory. MATLAB #174 was used to calculate the initial phase of diffractive surface of hybrid element and the initial phase matrix of diffraction surface was obtained. Then the coefficient value of the normalized radial aperture coordinate of diffraction surface was obtained by fitting the data. The diffraction and refraction surface structures of the element are optimized in Zemax #174.The final structural parameters of the hybrid element are obtained: the BK7 glass is selected as the lens material; The whole diameter of the element is 20.000mm, the diffractive plane diameter is 11.611mm, the center thickness is 2.004mm, the curvature of the convex surface is 66.542mm, the effective focal length is 95.257mm. The even power coefficients of the binary plane normalized radial aperture coordinates are respectively: -377.347335.116- 1174.462544.835- 130.274. At the same time, the effect of the refractive diffractive mixing element on increasing focal depth is simulated and analyzed. Theoretically, the focal depth of femtosecond laser beam can be increased to about 1.5mm, and the focal spot diameter is about 45.722 渭 m. Secondly, the hybrid element is made. The diffractive microstructures of the hybrid elements are fabricated by using the traditional intersecting method. According to the binary optics theory, the processing data of the components are calculated using L-edit#174.The mask plate is drawn by software, and the diffraction microstructure surface of the hybrid element is fabricated by photolithography experiment and plasma etching experiment. After the fabrication of the diffractive microstructure surface, the surface of the other side of the element is machined and the final hybrid element is obtained. Finally, the effect of the hybrid element is tested. The morphologies of the components were observed by using a microscope and a three-dimensional profilometer. Test elements on PMMA material increase focal depth level and exit focal spot size. The designed hybrid element can increase the focal depth of femtosecond laser beam to about 1.5mm, and the diameter of micropore on PMMA material is about 100 渭 m, which meets the requirement of femtosecond laser micromachining.
【学位授予单位】：北京工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN249
，
本文编号：2192111
[Abstract]:Compared with the long pulse laser, femtosecond laser has obvious threshold effect, the heat affected zone is very small, the recast layer is very small, and has a high controllability, which makes it play an extremely important role in micro fabrication. The focal depth and focal spot of the outgoing beam will directly affect the machining accuracy. In traditional optics, the focal depth and the focal spot restrict each other, so that the focal spot can not be diffused while increasing the focal depth. In this paper, the refractive-diffractive mixing element is selected to increase the focal depth of femtosecond laser beam, and the design and test process of the hybrid element is introduced from four aspects: theoretical analysis, simulation, fabrication and testing. The main contents are as follows: firstly, the surface parameters of the hybrid element are obtained by theoretical analysis and simulation. The design of the hybrid element follows the improved energy conservation method. According to the characteristic of Legend Elite femtosecond laser output beam and the design goal, the basic parameters of refractive-diffractive mixing element are determined, and the Fresnel diffraction theory is combined with Fresnel diffraction theory. MATLAB #174 was used to calculate the initial phase of diffractive surface of hybrid element and the initial phase matrix of diffraction surface was obtained. Then the coefficient value of the normalized radial aperture coordinate of diffraction surface was obtained by fitting the data. The diffraction and refraction surface structures of the element are optimized in Zemax #174.The final structural parameters of the hybrid element are obtained: the BK7 glass is selected as the lens material; The whole diameter of the element is 20.000mm, the diffractive plane diameter is 11.611mm, the center thickness is 2.004mm, the curvature of the convex surface is 66.542mm, the effective focal length is 95.257mm. The even power coefficients of the binary plane normalized radial aperture coordinates are respectively: -377.347335.116- 1174.462544.835- 130.274. At the same time, the effect of the refractive diffractive mixing element on increasing focal depth is simulated and analyzed. Theoretically, the focal depth of femtosecond laser beam can be increased to about 1.5mm, and the focal spot diameter is about 45.722 渭 m. Secondly, the hybrid element is made. The diffractive microstructures of the hybrid elements are fabricated by using the traditional intersecting method. According to the binary optics theory, the processing data of the components are calculated using L-edit#174.The mask plate is drawn by software, and the diffraction microstructure surface of the hybrid element is fabricated by photolithography experiment and plasma etching experiment. After the fabrication of the diffractive microstructure surface, the surface of the other side of the element is machined and the final hybrid element is obtained. Finally, the effect of the hybrid element is tested. The morphologies of the components were observed by using a microscope and a three-dimensional profilometer. Test elements on PMMA material increase focal depth level and exit focal spot size. The designed hybrid element can increase the focal depth of femtosecond laser beam to about 1.5mm, and the diameter of micropore on PMMA material is about 100 渭 m, which meets the requirement of femtosecond laser micromachining.
【学位授予单位】：北京工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN249
，
本文编号：2192111
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