时域整形电子动态调控飞秒激光非金属加工新方法

发布时间：2018-06-28 22:53

本文选题：飞秒激光 + 色散　；参考：《北京理工大学》2016年博士论文

【摘要】：飞秒激光微/纳制造是一个包含机械、热力学、光学、材料等多个学科的前沿交叉领域,在国防、医疗、信息等方面均有广泛应用。飞秒激光具有超高的峰值功率,其与材料作用是一个从纳米到毫米、从飞秒到微秒的非线性、非平衡多尺度过程,与传统制造的机理完全不同,因此,研究飞秒激光微/纳加工技术,对物理及制造科学本身都有着极其重要的意义。随着微小型化的进一步发展,对制造品质的要求不断提高,因此,飞秒激光微/纳制造也面临着新的挑战,如更高的加工质量,更高的加工效率和更好的加工可控性等。在理论上,飞秒激光与材料相互作用过程中,许多经典理论已不再适用,材料光学及热力学瞬时(飞秒)局部(纳米)特性的变化极其重要,需要引入量子力学,以提高其预测精度。在实验上,飞秒激光微/纳加工是一个多参数过程,涉及波长、波形、脉宽、频率等,但是激光波形和脉宽会在激光传输过程中因色散的引入而导致畸变或展宽,影响加工的精度及可重复性;此外,飞秒激光加工的表面质量、加工效率、可控性等仍需要进一步提高。因此,针对上述科学问题,本课题组基于电子动态调控的思想,提出利用飞秒激光时域整形的方法,解决脉冲的畸变及展宽,通过调控光子与电子的相互作用,控制材料局部瞬时光学和热力学特性,选择性激发材料相变,实现高质量、高效率、更高可控性的飞秒激光微/纳制造新方法。本论文主要研究了基于电子动态调控的时域整形飞秒激光加工非金属材料(电介质、聚合物和半导体),其主要内容包括:1)以高斯光束为例,建立了飞秒激光在介质中传输的色散模型,理论模拟并分析了二阶色散、三阶色散对飞秒激光脉冲的脉宽及脉冲时域形状的影响。2)建立了时域整形的飞秒激光与电介质材料相互作用的量子等离子体模型,深入的研究了自由电子的激发电离、加热以及材料瞬时局部光学特性的变化。3)搭建了时域整形的飞秒激光微/纳加工光路系统,系统的研究了时域整形飞秒激光参数对烧蚀弹坑的尺寸(直径、深度)及表面质量(重铸、微裂纹)的影响规律。4)理论推导了基于双光子聚合加工的特征尺寸与激光辐照参数的关系,利用时域整形的飞秒激光进行聚合加工,实现了λ/12的极限分辨尺寸。5)提出了利用时域整形的飞秒激光高效率制备微流体通道的新方法,并研究了各参数对微通道加工效率的影响规律。6)研究了时域整形的飞秒激光直写加工半导体硅的各向异性现象,提出了通过调控飞秒激光的扫描速度、扫描方向和偏振方向,进而调控半导体材料表面周期结构的方向及几何形貌。本论文所取得的主要创新成果总结如下:1)提出利用时域整形的飞秒激光加工电介质,通过调控电子激发、电离、复合及相变过程,实现高精度、高质量的微/纳加工新方法。首先,通过改变脉冲序列的子脉冲间隔,发现100 fs-200 fs之间烧蚀增强的新现象。其次,通过改变脉冲序列的子脉冲个数,调控烧蚀结构直径和深度。最后,通过改变脉冲序列的能量分配比,实现对相变的选择性激发,从而减少重铸,提高了材料的表面加工质量。2)提出利用时域整形的飞秒激光在电介质上加工微流体通道,通过调控自由电子密度分布,实现高效率的微/纳加工新方法。首先,提出利用液体辅助飞秒激光脉冲序列的方法在电介质材料上加工微通道结构,在相同条件下,加工效率提高了56倍,单次扫描加工微通道的极限深径比提高了3倍。其次,提出了利用飞秒激光脉冲序列辐照改性化学刻蚀的方法加工微通道结构,在相同的条件下,辐照区域的刻蚀效率提高了10倍;提出了通过匀减速的扫描方法,改善微通道的截面形状,实现了优化加工。最后,提出利用飞秒激光脉冲序列的方法消除激光偏振对辐照改性区域的影响,实现各向同性的微通道化学刻蚀加工。3)首次发现时域整形的线偏振飞秒激光在硅材料表面直写加工的各向异性新现象,通过调控材料表面等离子体的形成及分布,实现可控性表面微/纳加工新方法。在固定点加工中,通过改变脉冲序列子脉冲间隔,调控表面结构的周期及形貌;在激光直写中,首次发现并提出了线偏振的飞秒激光在硅材料表面直写加工的各向异性现象,提出通过改变飞秒激光的偏振、扫描方向、扫描速度等参数,调控表面结构的几何形貌及方向。
[Abstract]:Femtosecond laser micro / nano manufacturing is a frontier area which includes mechanical, thermodynamic, optical, material and other disciplines. It is widely used in defense, medical, information and so on. Femtosecond laser has ultra high peak power, and its function is a nonlinear, nonequilibrium multiscale process from nanometer to millisecond, from femtosecond to microsecond. It is quite different from the traditional manufacturing mechanism. Therefore, the study of femtosecond laser micro / nanofabrication technology is of great importance to the physics and manufacturing science itself. With the further development of microminiaturization, the requirements for the manufacturing quality are increasing. Therefore, the femtosecond laser micro / nano manufacturing is also facing new challenges, such as higher processing quality. In theory, in the process of interaction between femtosecond laser and material, many classical theories are no longer applicable, and the change of optical and thermodynamic instantaneous (femtosecond) local (nanometer) characteristics is very important. Quantum mechanics is needed to improve its prediction accuracy. In experiment, femtosecond laser Micro / nano machining is a multi parameter process involving wavelengths, waveforms, pulse width and frequency, but the laser wave and pulse width will distort or widen in the process of laser transmission due to the introduction of dispersion, and affect the accuracy and repeatability of the processing. In addition, the surface quality, processing efficiency and controllability of the femtosecond laser processing need to be further improved. Therefore, in view of the above scientific problems, the research group, based on the idea of electronic dynamic regulation, proposes to use the method of femtosecond laser time domain shaping to solve the distortion and broadening of the pulse. By controlling the interaction between the photon and the electron, the local instantaneous optical and thermodynamic properties of the material are controlled, the phase transition of the material is selectively excited and the high quality and high efficiency are realized. A new method of femtosecond laser micro / nano fabrication with higher controllability. This paper mainly studies the time-domain shaping femtosecond laser processing nonmetallic materials (dielectric, polymer and semiconductor) based on electronic dynamic regulation and control. The main contents include: 1) the dispersion model of femtosecond laser propagation in the medium is established with Gauss beam as an example. The theoretical model is established. The effects of the two order dispersion, the three order dispersion on the pulse width and the pulse time domain shape of the femtosecond laser pulse are analyzed and analyzed. The quantum plasma model of the interaction of the femtosecond laser with the dielectric material in the time domain is established. The excited ionization of the free electrons, the heat addition and the change of the instantaneous local optical properties of the material are studied in depth. The two order dispersion and the influence of the three order dispersion on the pulse time domain shape of the femtosecond laser pulse are established. A femtosecond laser micro / nanofabrication optical path system in time domain shaping is built. The effect of time domain shaping femtosecond laser parameters on the size (diameter, depth) and surface quality (recasting, micro crack) of the ablation crater is systematically studied. The relationship between the characteristic size of the two-photon polymerization and the laser irradiation parameters based on the two-photon polymerization is derived, and the use of the.4 is derived. The domain shaping femtosecond laser is polymerized and the limit resolution size.5 of lambda /12 is realized. A new method of high efficiency preparation of microfluidic channel using femtosecond laser in time domain shaping is proposed, and the effect of each parameter on the processing efficiency of microchannel.6) is studied. The orientation and geometry of the periodic structure of the semiconductor material are regulated by regulating the scanning speed, the direction and the direction of polarization of the femtosecond laser. The main achievements in this paper are summarized as follows: 1) the processing of the dielectric by using the femtosecond laser in time domain is proposed, and the electronic excitation and electricity are regulated by the control of electronic excitation. A new method of high precision and high quality micro / nano machining. First, a new phenomenon of ablation enhancement between 100 FS-200 FS is discovered by changing the interval of the pulse sequence. Secondly, the diameter and depth of the ablation structure are regulated by changing the number of subpulses in the pulse sequence. Finally, the energy of the pulse sequence is changed. A new method of micro / nanofabrication is realized by using time domain shaping femtosecond laser to process the microfluidic channel on the dielectric. By adjusting the density distribution of free electrons, a new efficient micro / nanofabrication method is realized by using the time domain shaping femtosecond laser in the dielectric. First, the liquid assisted femtosecond excitation is proposed. The method of optical pulse sequence is used to process microchannel structure on dielectric material. Under the same condition, the machining efficiency is increased by 56 times. The limit depth diameter ratio of the single scanning micro channel is 3 times higher. Secondly, the microchannel structure is processed by using the femtosecond laser pulse sequence to irradiate the modified chemical etching. The etching efficiency of the region is increased by 10 times, and the shape of the microchannel cross section is improved by the uniform deceleration method. Finally, the effect of the laser polarization on the irradiated region is eliminated by the method of the femtosecond laser pulse sequence, and the isotropic microchannel chemical etching process.3 is first discovered. A new anisotropic new phenomenon of linear polarization femtosecond laser processing on the surface of silicon material. By regulating the formation and distribution of the surface plasma of the material, a new method of controllable surface micro / nanofabrication is realized. In the fixed point processing, the periodic and morphology of the surface structure are regulated by changing the pulse interval of the pulse sequence, and the laser is straight. In writing, the isotropic phenomenon of linear polarization of femtosecond laser on the surface of silicon material is discovered and proposed for the first time. The geometric morphology and direction of the surface structure are regulated by changing the polarization, scanning direction and scanning speed of the femtosecond laser.
【学位授予单位】：北京理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG665

【参考文献】