【作者】 赵亮；

【导师】 胡湛；

【作者基本信息】 吉林大学 ， 原子与分子物理， 2019， 硕士

【摘要】 近年来,飞秒激光对材料的烧蚀研究领域得到了广泛的关注,飞秒激光微加工技术并在工业加工领域有着良好的应用前景。飞秒脉冲激光脉宽较短,材料烧蚀过程中热影响区域小,而整形飞秒激光不仅具有此优点,并且可以任意改变脉冲形状实现对烧蚀过程的有效控制,因此整形飞秒激光将在微加工领域呈现出更多的优势。本文采用整形飞秒激光脉冲烧蚀单晶铜和GDP薄膜,通过大量实验数据分析了整形飞秒激光烧蚀单晶铜的物理机制和GDP薄膜微孔形成的规律,具体的研究内容如下:(1)使用整形飞秒激光对单晶铜的进行单脉冲烧蚀,探究了不同能量通量下整形飞秒激光子脉冲个数及相邻子脉冲时间间隔的变化对烧蚀坑深度、表面积、体积和坑内形貌的影响。实验结果表明随着相邻子脉冲时间间隔的增加,烧蚀坑的深度逐渐减小,表面积逐渐增大,且深度的变化率大于表面积的变化率,因此烧蚀坑体积随子脉冲时间间隔的增加而减小。深度、表面积、体积等参数的变化趋势在不同的能量通量条件下相同,但变化的程度不同。我们结合受激辐射热传导机制、等离子体的屏蔽机制、电子-晶格耦合机制等几个方面对深度、表面积和体积的变化趋势进行了分析和解释。(2)在整形飞秒激光对GDP薄膜进行的钻孔实验中,探究了不同能量通量、整形飞秒激光(脉冲序列)子脉冲个数及子脉冲时间间隔对烧蚀孔的尺寸和形貌产生的影响,获得了适用于GDP薄膜钻孔的整形条件。实验结果显示:相同能量通量条件下,烧蚀孔的尺寸、圆度及形貌与整形飞秒激光脉冲的子脉冲个数和子脉冲时间间隔有关。三个能量条件下的变换极限脉冲和子脉冲间隔小的三脉冲序列获得的后孔质量较差并在后孔周围有碎裂现象;相同能量条件下,七脉冲序列烧蚀孔质量更优且圆度更好,前后孔直径随子脉冲间隔增加而减小;子脉冲个数较少时,即三脉冲序列,能量对烧蚀孔的直径影响较大,能量越大获得的前后孔直径越大而前后孔直径差值无明显变化;当子脉冲个数较多时,即七脉冲序列,能量对烧蚀孔的直径以及直径的差值影响都较小。更多还原

【Abstract】 In recent years,more and more research interest has been put into the field of femtosecond laser ablation of materials,femtosecond laser micromachining has good prospects in industrial fabrication.Femtosecond lasers have short laser pulse,thus a small heat affected zone,shaped femtosecond laser pulse has even more advantage that the pulse shape can be changed to further control the ablation process,hence it will benefit micromachining even more.In this thesis,we use shaped femtosecond laser pulse to ablate single crystal copper and GDP film.The mechanism of single-crystal copper ablated by femtosecond shaped laser pulse and the formation of micro-holes in GDP films are analyzed.The research mainly includes the following aspects: In the experiment of single crystal copper ablated by femtosecond shaped-pules,investigation on how the numbers and interval of sub-pulses femtosecond laser pulses in the shaped pulse sequences with different energy fluxes influence the ablation depth,surface area,volume and crater morphology was performed.Results show that with the increase of sub-pulse interval,the ablation depth decreases gradually,nevertheless the surface area expands gradually.The gradient of depth is greater than that of surface area.Therefore,the ablation volume decreases with the increase of sub-pulse time interval.In this work,the plasma shielding mechanism,electron lattice coupling mechanism,electron heating mechanism have been carried on the analysis to the regularity of ablation depth,surface area and volume.The morphology of the ablation crater is further studied by combining the profile curve of the ablation crater and the analysis curve of the falling ash in the ablation crater.In the drilling experiments of femtosecond shaped pulses on GDP thin films,the effects of numbers and interval of sub-pulses in shaped-pulse sequence with various energy fluxes on the size and shape of ablation holes were investigated,the optimal pulse-shaping parameters for GDP drilling were obtained.Results show that the size,roundness and morphology of the ablation hole depend on the numbers and interval of sub-pulses in the shaped pulses with identical energy flux.In the drilling by transform limit pulses and three pulse sequences with small interval,three different energies were employed,the exit qualities of all three cases are decent and there are cracks around the exits.In conditions of an identical energy,the ablation hole drilled by the seven-pulse sequence presents better quality and roundness,the entrance diameters together with exit ones decline while the sub-pulse interval increases;when the number of sub-pulses is small,e.g.the three-pulse sequence,the diameter of the ablation hole has a strong dependence on the pulse energy,in which the higher energy leads to larger diameters of both entrance and exit,but the difference between diameters of the entrance and exit is rather small.When the number of sub-pulses is large,that is,the seven-pulse sequence,the diameters and difference between diameters of the front and back holes show weak response to the pulse energy.Because of the extremely short duration and the formidable peak power,femtosecond laser pulse fabricate little heat affected zone in ablation process,which makes femtosecond laser pulse a luminary in kinds of industrial micro-fabrication.Femtosecond shaped laser pulse possesses not only the advantage of femtosecond laser pulse but also the ability to control the ablation process with various pulse shapes.Thus,femtosecond laser pulse-shaping technique presents better effect in micro-fabrication.In this thesis,the single-crystal copper and GDP film were ablated by femtosecond shaped laser pulse.The mechanism of single-crystal copper ablated by femtosecond shaped laser pulse and the formation of micro-holes in GDP films are analyzed.The research mainly includes the following aspects:In the experiment of single crystal copper ablated by femtosecond shaped-pules,investigation on how the numbers and interval of sub-pulses femtosecond laser pulses in the shaped pulse sequences with different energy fluxes influence the ablation depth,surface area,volume and crater morphology was performed.Results show that with the increase of sub-pulse interval,the ablation depth decreases gradually,nevertheless the surface area expands gradually.The gradient of depth is greater than that of surface area.Therefore,the ablation volume decreases with the increase of sub-pulse time interval.In this work,the plasma shielding mechanism,electron lattice coupling mechanism,electron heating mechanism have been carried on the analysis to the regularity of ablation depth,surface area and volume.The morphology of the ablation crater is further studied by combining the profile curve of the ablation crater and the analysis curve of the falling ash in the ablation crater.In the drilling experiments of femtosecond shaped pulses on GDP thin films,the effects of numbers and interval of sub-pulses in shaped-pulse sequence with various energy fluxes on the size and shape of ablation holes were investigated,the optimal pulse-shaping parameters for GDP drilling were obtained.Results show that the size,roundness and morphology of the ablation hole depend on the numbers and interval of sub-pulses in the shaped pulses with identical energy flux.In the drilling by transform limit pulses and three pulse sequences with small interval,three different energies were employed,the exit qualities of all three cases are decent and there are cracks around the exits.In conditions of an identical energy,the ablation hole drilled by the seven-pulse sequence presents better quality and roundness,the entrance diameters together with exit ones decline while the sub-pulse interval increases;when the number of sub-pulses is small,e.g.the three-pulse sequence,the diameter of the ablation hole has a strong dependence on the pulse energy,in which the higher energy leads to larger diameters of both entrance and exit,but the difference between diameters of the entrance and exit is rather small.When the number of sub-pulses is large,that is,the seven-pulse sequence,the diameters and difference between diameters of the front and back holes show weak response to the pulse energy.更多还原